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                            <b>2.1.1.</b>
                        
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                        Interactive vs Non-Interactive Shell
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                        Login vs Non-Login Shell
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                            <b>2.9.</b>
                        
                        etc
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                            <b>3.</b>
                        
                        Test
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                            <b>3.1.</b>
                        
                        Operators
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                            <b>4.</b>
                        
                        Subshells
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                            <b>4.1.</b>
                        
                        Process Creation
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                            <b>5.</b>
                        
                        Commands
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                            <b>5.1.</b>
                        
                        Builtin Commands
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                            <b>5.1.1.</b>
                        
                        read
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                            <b>5.1.2.</b>
                        
                        printf
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                            <b>5.1.3.</b>
                        
                        eval
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                        getopts
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                        Keyword Commands
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                        Compound Commands
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                        Special Commands
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                        expr
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                            <b>5.5.</b>
                        
                        grep
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                            <b>5.6.</b>
                        
                        find
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                            <b>5.7.</b>
                        
                        xargs
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                            <b>6.</b>
                        
                        Arrays
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                            <b>7.</b>
                        
                        Shell Metacharacters
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                            <b>7.1.</b>
                        
                        Precedence
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                            <b>8.</b>
                        
                        Expansions and Substitutions
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                            <b>8.1.</b>
                        
                        Brace Expansion
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                            <b>8.2.</b>
                        
                        Tilde Expansion
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                            <b>8.3.</b>
                        
                        Parameter Expansion
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                            <b>8.4.</b>
                        
                        Arithmetic Expansion
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                            <b>8.5.</b>
                        
                        Command Substitution
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                            <b>8.6.</b>
                        
                        Process Substitution
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                            <b>8.7.</b>
                        
                        Word Splitting
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                            <b>8.8.</b>
                        
                        Filename Expansion
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                            <b>9.</b>
                        
                        Job Control
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                            <b>9.1.</b>
                        
                        Session and Process Group
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                            <b>9.2.</b>
                        
                        Process State Codes
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                            <b>9.3.</b>
                        
                        TTY
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                            <b>9.4.</b>
                        
                        Mutual Exclusion
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                            <b>10.</b>
                        
                        Redirections
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                            <b>10.1.</b>
                        
                        File Descriptors
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                            <b>10.2.</b>
                        
                        &lt;&lt; , &lt;&lt;&lt;
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                            <b>10.3.</b>
                        
                        Pipe
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                            <b>10.4.</b>
                        
                        Named Pipe
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                            <b>10.5.</b>
                        
                        Buffering
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                            <b>11.</b>
                        
                        Signals and Traps
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                            <b>11.1.</b>
                        
                        kill
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                            <b>11.2.</b>
                        
                        trap
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                            <b>11.3.</b>
                        
                        Signals Table
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                            <b>12.</b>
                        
                        Command Aliases
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        <li class="chapter " data-level="13" data-path="command_history.html">
            
                
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                            <b>13.</b>
                        
                        Command History
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                            <b>14.</b>
                        
                        Command Completion
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        <li class="chapter " data-level="15" data-path="readline.html">
            
                
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                            <b>15.</b>
                        
                        Readline
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        <li class="chapter " data-level="16" data-path="colors_and_prompt.html">
            
                
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                            <b>16.</b>
                        
                        Colors and Prompt
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        <li class="chapter " data-level="17" data-path="shell_variables.html">
            
                
                    <a href="./shell_variables.html">
                
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                            <b>17.</b>
                        
                        Shell Variables
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        <li class="chapter " data-level="17.1" data-path="positional_parameters.html">
            
                
                    <a href="./positional_parameters.html">
                
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                            <b>17.1.</b>
                        
                        Positional Parameters
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        <li class="chapter " data-level="17.2" data-path="special_parameters.html">
            
                
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                            <b>17.2.</b>
                        
                        Special Parameters
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        <li class="chapter " data-level="18" data-path="shell_options.html">
            
                
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                            <b>18.</b>
                        
                        Shell Options
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        <li class="chapter " data-level="18.1" data-path="command_line_options.html">
            
                
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                            <b>18.1.</b>
                        
                        Command-line options
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        <li class="chapter " data-level="19" data-path="debugging.html">
            
                
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                            <b>19.</b>
                        
                        Debugging
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        <li class="chapter " data-level="20" data-path="locale.html">
            
                
                    <a href="./locale.html">
                
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                            <b>20.</b>
                        
                        Locale
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                            <b>21.</b>
                        
                        sh
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                            <b>22.</b>
                        
                        Tips
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                        맺음말
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                            <b>24.</b>
                        
                        별책부록
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                    <section class="normal" id="section-">
                    
                        <h1 id="proc">/proc</h1>
<p>&#xC774; &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB294; &#xD604;&#xC7AC; &#xC2DC;&#xC2A4;&#xD15C;&#xC5D0;&#xC11C; &#xC2E4;&#xD589;&#xB418;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC5D0; &#xB300;&#xD55C; &#xC815;&#xBCF4;&#xB97C; &#xC81C;&#xACF5;&#xD558;&#xAE30; &#xC704;&#xD574;
OS &#xC5D0;&#xC11C; &#xC81C;&#xACF5;&#xD558;&#xB294; &#xAC00;&#xC0C1;&#xC758; &#xD30C;&#xC77C;&#xC2DC;&#xC2A4;&#xD15C; &#xC785;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB7EC;&#xB2C8;&#xAE4C; &#xC2E4;&#xC81C; &#xD30C;&#xC77C;&#xC774; &#xC874;&#xC7AC;&#xD558;&#xB294; &#xAC83;&#xC774; &#xC544;&#xB2D9;&#xB2C8;&#xB2E4;.
&#xCEE4;&#xB110;&#xC774; &#xAC00;&#xC9C0;&#xACE0; &#xC788;&#xB294; &#xC815;&#xBCF4;&#xB294; &#xC0AC;&#xC6A9;&#xC790; &#xD504;&#xB85C;&#xADF8;&#xB7A8;&#xC5D0;&#xC11C; &#xC9C1;&#xC811; &#xC811;&#xADFC;&#xD560; &#xC218;&#xAC00; &#xC5C6;&#xC73C;&#xBBC0;&#xB85C;
system call &#xC744; &#xD1B5;&#xD574; &#xC81C;&#xACF5;&#xD558;&#xB294; &#xBC29;&#xBC95;&#xB3C4; &#xC0DD;&#xAC01;&#xD574; &#xBCFC; &#xC218; &#xC788;&#xACA0;&#xC73C;&#xB098; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xAC00;&#xC9C0;&#xB294;
&#xC790;&#xB8CC;&#xAD6C;&#xC870;&#xB97C; &#xC0DD;&#xAC01;&#xD560;&#xB54C; &#xC0AC;&#xC6A9;&#xC790;&#xAC00; &#xC27D;&#xAC8C; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xB3C4;&#xB85D; &#xBA54;&#xBAA8;&#xB9AC;&#xC0C1;&#xC5D0; &#xAC00;&#xC0C1;&#xC758; &#xD30C;&#xC77C; &#xC2DC;&#xC2A4;&#xD15C;&#xC744;
&#xB9CC;&#xB4E4;&#xC5B4;&#xC11C; &#xAD6C;&#xC870;&#xC801;&#xC73C;&#xB85C; &#xC81C;&#xACF5;&#xD558;&#xB294; &#xAC83;&#xC785;&#xB2C8;&#xB2E4;.
&#xAC01;&#xAC01;&#xC758; &#xD30C;&#xC77C;&#xC740; &#xCEE4;&#xB110; &#xB0B4;&#xBD80;&#xC758; &#xD2B9;&#xC815; &#xD568;&#xC218;&#xC640; &#xC5F0;&#xACB0;&#xB418;&#xC5B4; &#xC788;&#xC5B4;&#xC11C; read &#xD558;&#xBA74; &#xC2E4;&#xC2DC;&#xAC04;&#xC73C;&#xB85C; &#xD574;&#xB2F9; &#xC815;&#xBCF4;&#xAC00; &#xD45C;&#xC2DC;&#xB429;&#xB2C8;&#xB2E4;. ( &#xBA54;&#xBAA8;&#xB9AC; &#xC774;&#xBBC0;&#xB85C; &#xC18D;&#xB3C4;&#xAC00; &#xBE60;&#xB985;&#xB2C8;&#xB2E4; ).</p>
<p>&#xC774;&#xC640; &#xAC19;&#xC740; &#xC815;&#xBCF4;&#xC81C;&#xACF5; &#xBC29;&#xBC95;&#xC774; &#xC720;&#xC6A9;&#xD55C; &#xC810;&#xC774; &#xB9CE;&#xAE30; &#xB54C;&#xBB38;&#xC5D0; &#xC9C0;&#xAE08;&#xC740; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xC815;&#xBCF4;&#xBFD0;&#xB9CC; &#xC544;&#xB2C8;&#xB77C;
&#xCEE4;&#xB110;&#xC774; &#xAC00;&#xC9C0;&#xACE0; &#xC788;&#xB294; &#xC5EC;&#xB7EC;&#xAC00;&#xC9C0; &#xC2DC;&#xC2A4;&#xD15C; &#xAD00;&#xB828; &#xC815;&#xBCF4;&#xB3C4; /proc &#xB97C; &#xD1B5;&#xD574; &#xC81C;&#xACF5;&#xD558;&#xACE0; &#xC788;&#xACE0;
&#xCEE4;&#xB110; &#xD30C;&#xB77C;&#xBBF8;&#xD130; &#xAC12;&#xC744; write &#xC744; &#xD1B5;&#xD574; &#xBCC0;&#xACBD;&#xD560; &#xC218;&#xB3C4; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># `ps` &#xBA85;&#xB839;&#xC740; &#xBAA8;&#xB4E0; &#xC815;&#xBCF4;&#xB97C; /proc &#xB97C; &#xC774;&#xC6A9;&#xD574; &#xD45C;&#xC2DC;&#xD569;&#xB2C8;&#xB2E4;.</span>

$ strace <span class="hljs-operator">-e</span> openat ps |&amp; grep /proc/
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/self/auxv&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/sys/kernel/osrelease&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/self/auxv&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/self/stat&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/uptime&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/sys/kernel/pid_max&quot;</span>, O_RDONLY) = <span class="hljs-number">4</span>
. . .
----------------------------------------------------

<span class="hljs-comment"># vmstat &#xBA85;&#xB839;</span>
$ strace <span class="hljs-operator">-e</span> openat vmstat |&amp; grep /proc/ 
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/self/auxv&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/sys/kernel/osrelease&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/self/auxv&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/sys/kernel/osrelease&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/meminfo&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/stat&quot;</span>, O_RDONLY) = <span class="hljs-number">4</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/vmstat&quot;</span>, O_RDONLY) = <span class="hljs-number">5</span>

<span class="hljs-comment"># netstat &#xBA85;&#xB839;</span>
$ strace <span class="hljs-operator">-e</span> openat netstat |&amp; grep /proc/     
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/filesystems&quot;</span>, O_RDONLY|O_CLOEXEC) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/net/tcp&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/net/tcp6&quot;</span>, O_RDONLY) = <span class="hljs-number">3</span>
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/net/sctp/eps&quot;</span>, O_RDONLY) = -<span class="hljs-number">1</span> ENOENT (No such file or directory)
openat(AT_FDCWD, <span class="hljs-string">&quot;/proc/net/sctp6/eps&quot;</span>, O_RDONLY) = -<span class="hljs-number">1</span> ENOENT (No such file or directory)
. . .

<span class="hljs-comment"># /proc &#xB97C; &#xC0AC;&#xC6A9; &#xC911;&#xC778; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4; </span>
$ ps f $( fuser -m /proc <span class="hljs-number">2</span>&gt; /dev/null )
. . .
</code></pre>
<p>/proc &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB97C; ls &#xD588;&#xC744;&#xB54C; &#xBCF4;&#xC774;&#xB294; &#xC22B;&#xC790;&#xB85C;&#xB41C; &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xAC00; &#xD604;&#xC7AC; &#xC2DC;&#xC2A4;&#xD15C;&#xC5D0;&#xC11C; &#xC2E4;&#xD589;&#xB418;&#xACE0; &#xC788;&#xB294;
&#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC785;&#xB2C8;&#xB2E4;.
&#xC608;&#xB97C; &#xB4E4;&#xC5B4; &#xD604;&#xC7AC; bash shell &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC640; &#xAD00;&#xB828;&#xB41C; &#xC815;&#xBCF4;&#xB97C; &#xBCF4;&#xB824;&#xBA74; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; &#xD558;&#xBA74; &#xB429;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># &apos;$$&apos; &#xB294; &#xD604;&#xC7AC; shell pid &#xB97C; &#xB098;&#xD0C0;&#xB0B4;&#xB294; &#xD2B9;&#xC218;&#xBCC0;&#xC218; &#xC785;&#xB2C8;&#xB2E4;.</span>
$ ls <span class="hljs-operator">-l</span> /proc/$$/
total <span class="hljs-number">0</span>
dr-xr-xr-x <span class="hljs-number">2</span> mug896 mug896 <span class="hljs-number">0</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">04</span>:<span class="hljs-number">48</span> attr/
-rw-r--r-- <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">0</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">04</span>:<span class="hljs-number">48</span> autogroup
-r-------- <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">0</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">04</span>:<span class="hljs-number">48</span> auxv
-r--r--r-- <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">0</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">04</span>:<span class="hljs-number">48</span> cgroup
--w------- <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">0</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">04</span>:<span class="hljs-number">48</span> clear_refs
-r--r--r-- <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">0</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">04</span>:<span class="hljs-number">48</span> cmdline
. . .

<span class="hljs-comment"># &#xD604;&#xC7AC; shell &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xAC00;&#xC9C0;&#xACE0; &#xC788;&#xB294; file descriptors</span>
$ ls <span class="hljs-operator">-l</span> /proc/$$/fd/
total <span class="hljs-number">0</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">05</span>:<span class="hljs-number">06</span> <span class="hljs-number">0</span> -&gt; /dev/pts/<span class="hljs-number">2</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">05</span>:<span class="hljs-number">06</span> <span class="hljs-number">1</span> -&gt; /dev/pts/<span class="hljs-number">2</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">05</span>:<span class="hljs-number">06</span> <span class="hljs-number">2</span> -&gt; /dev/pts/<span class="hljs-number">2</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2017</span>-<span class="hljs-number">02</span>-<span class="hljs-number">18</span> <span class="hljs-number">05</span>:<span class="hljs-number">06</span> <span class="hljs-number">255</span> -&gt; /dev/pts/<span class="hljs-number">2</span>
</code></pre>
<p>&#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774;&#xD558;&#xBA74; &#xD604;&#xC7AC; libcairo.so &#xB77C;&#xC774;&#xBE0C;&#xB7EC;&#xB9AC;&#xB97C; &#xC0AC;&#xC6A9; &#xC911;&#xC778; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xBAA9;&#xB85D;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ sudo grep libcairo.so /proc/[<span class="hljs-number">1</span>-<span class="hljs-number">9</span>]*/maps
</code></pre>
<p>&#xD604;&#xC7AC; &#xC2DC;&#xC2A4;&#xD15C;&#xC5D0; &#xC0DD;&#xC131;&#xB418;&#xC5B4; &#xC788;&#xB294; &#xC804;&#xCCB4; &#xC2A4;&#xB808;&#xB4DC;&#xC758; waiting channel 
( &#xC2A4;&#xB808;&#xB4DC;&#xAC00; block &#xC0C1;&#xD0DC;&#xC5D0; &#xC788;&#xB294; &#xCEE4;&#xB110; &#xD568;&#xC218; ) &#xD1B5;&#xACC4;.</p>
<pre><code class="lang-bash">$ <span class="hljs-keyword">for</span> tid <span class="hljs-keyword">in</span> /proc/[<span class="hljs-number">1</span>-<span class="hljs-number">9</span>]*/task/*; <span class="hljs-keyword">do</span> cat <span class="hljs-variable">$tid</span>/wchan; <span class="hljs-built_in">echo</span>; <span class="hljs-keyword">done</span> |
                                     sort -n | uniq -c | sort -nr
    <span class="hljs-number">739</span> futex_<span class="hljs-built_in">wait</span>_queue_me
    <span class="hljs-number">365</span> <span class="hljs-number">0</span>                         <span class="hljs-comment"># &#xAC12;&#xC774; 0 &#xC778;&#xAC83;&#xC740; &#xD604;&#xC7AC; wait &#xC0C1;&#xD0DC;&#xAC00; &#xC544;&#xB2D8;</span>
    <span class="hljs-number">272</span> <span class="hljs-keyword">do</span>_poll.constprop.<span class="hljs-number">0</span>
     <span class="hljs-number">87</span> ep_poll
     <span class="hljs-number">20</span> <span class="hljs-keyword">do</span>_select 
     <span class="hljs-number">13</span> __skb_<span class="hljs-built_in">wait</span>_<span class="hljs-keyword">for</span>_more_packets       $ sudo cat /proc/$$/task/$$/stack
      <span class="hljs-number">8</span> pipe_<span class="hljs-built_in">read</span>                         [&lt;<span class="hljs-number">0</span>&gt;] <span class="hljs-keyword">do</span>_<span class="hljs-built_in">wait</span>+<span class="hljs-number">0</span>x1ae/<span class="hljs-number">0</span>x220
      <span class="hljs-number">7</span> <span class="hljs-keyword">do</span>_<span class="hljs-built_in">wait</span>                           [&lt;<span class="hljs-number">0</span>&gt;] kernel_<span class="hljs-built_in">wait</span>4+<span class="hljs-number">0</span>xaf/<span class="hljs-number">0</span>x150
      <span class="hljs-number">5</span> fuse_dev_<span class="hljs-keyword">do</span>_<span class="hljs-built_in">read</span>                  [&lt;<span class="hljs-number">0</span>&gt;] __<span class="hljs-keyword">do</span>_sys_<span class="hljs-built_in">wait</span>4+<span class="hljs-number">0</span>x84/<span class="hljs-number">0</span>x90
      <span class="hljs-number">3</span> unix_stream_data_<span class="hljs-built_in">wait</span>             [&lt;<span class="hljs-number">0</span>&gt;] __x64_sys_<span class="hljs-built_in">wait</span>4+<span class="hljs-number">0</span>x1e/<span class="hljs-number">0</span>x20
      <span class="hljs-number">1</span> hrtimer_nanosleep                 [&lt;<span class="hljs-number">0</span>&gt;] <span class="hljs-keyword">do</span>_syscall_64+<span class="hljs-number">0</span>x49/<span class="hljs-number">0</span>xc0
      <span class="hljs-number">1</span> <span class="hljs-keyword">do</span>_signal_stop                    [&lt;<span class="hljs-number">0</span>&gt;] entry_SYSCALL_64_after_hwframe+<span class="hljs-number">0</span>x44/<span class="hljs-number">0</span>xa9
</code></pre>
<p><code>/proc/[1-9]*/stat</code> &#xC744; &#xC774;&#xC6A9;&#xD574; gdm3 &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; &#xC790;&#xC190; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xB4E4;&#xC744; &#xCD9C;&#xB825;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># $1 &#xB294; PID, $4 &#xB294; PPID </span>
$ awk -v PPID=`pidof gdm3` -v FPAT=<span class="hljs-string">&apos;[^ ]+|\\([^\\)]*\\)&apos;</span> <span class="hljs-string">&apos;
    { a[$1] = $4 } END{ print PPID; desc(PPID) }
function desc( ppid,   i) {
    for ( i in a ) { if ( a[i] == ppid ) { print i; desc(i) }}
}
&apos;</span> /proc/[<span class="hljs-number">1</span>-<span class="hljs-number">9</span>]*/<span class="hljs-built_in">stat</span> | xargs ps f
    PID TTY      STAT   TIME COMMAND
   <span class="hljs-number">1492</span> ?        Ssl    <span class="hljs-number">0</span>:<span class="hljs-number">00</span> /usr/sbin/gdm3
   <span class="hljs-number">1498</span> ?        Sl     <span class="hljs-number">0</span>:<span class="hljs-number">00</span>  \_ gdm-session-worker [pam/gdm-autologin]
   <span class="hljs-number">1531</span> tty2     Ssl+   <span class="hljs-number">0</span>:<span class="hljs-number">00</span>      \_ /usr/libexec/gdm-x-session --register-session ...
   <span class="hljs-number">1533</span> tty2     Sl+   <span class="hljs-number">28</span>:<span class="hljs-number">21</span>          \_ /usr/lib/xorg/Xorg vt2 -displayfd <span class="hljs-number">3</span> ...
   <span class="hljs-number">1640</span> tty2     Sl+    <span class="hljs-number">0</span>:<span class="hljs-number">00</span>          \_ /usr/bin/startplasma-x11
   <span class="hljs-number">1745</span> ?        Ss     <span class="hljs-number">0</span>:<span class="hljs-number">00</span>              \_ /usr/bin/ssh-agent /usr/bin/im-launch ...
</code></pre>
<h4 id="procself">/proc/self</h4>
<p>/proc/self &#xB294; &#xC2EC;&#xBCFC;&#xB9AD;&#xB9C1;&#xD06C; &#xC778;&#xB370; &#xD56D;&#xC0C1; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xC790;&#xC2E0;&#xC758; PID &#xBC88;&#xD638;&#xC5D0; &#xC5F0;&#xACB0;&#xB418;&#xC5B4; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB7EC;&#xBBC0;&#xB85C; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xC790;&#xC2E0;&#xC758; &#xC815;&#xBCF4;&#xB97C; &#xAD6C;&#xD558;&#xB824;&#xACE0; &#xD560;&#xACBD;&#xC6B0; &#xB530;&#xB85C; PID &#xB97C; &#xC54C;&#xC544;&#xB0BC; &#xD544;&#xC694;&#xC5C6;&#xC774;
/proc/self &#xB97C; &#xC774;&#xC6A9;&#xD558;&#xBA74; &#xB429;&#xB2C8;&#xB2E4;.
/dev &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xC5D0; &#xC874;&#xC7AC;&#xD558;&#xB294; <code>fd</code>, <code>stdin</code>, <code>stdout</code>, <code>stderr</code> &#xB3C4; &#xBAA8;&#xB450; /proc/self &#xC640; &#xC5F0;&#xACB0;&#xB41C; &#xB9C1;&#xD06C;&#xB85C;
shell script &#xB97C; &#xC791;&#xC131;&#xD560; &#xB54C; &#xC720;&#xC6A9;&#xD558;&#xAC8C; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">/dev/fd     -&gt; /proc/self/fd
/dev/stdin  -&gt; /proc/self/fd/<span class="hljs-number">0</span>
/dev/stdout -&gt; /proc/self/fd/<span class="hljs-number">1</span>
/dev/stderr -&gt; /proc/self/fd/<span class="hljs-number">2</span>

<span class="hljs-comment"># &#xC608;&#xB97C; &#xB4E4;&#xC5B4; ls &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xBA74; self &#xB294; ls &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xB418;&#xACE0;</span>
<span class="hljs-comment"># date &#xBA85;&#xB839;&#xC744; &#xC2E4;&#xD589;&#xD558;&#xBA74; self &#xB294; date &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; &#xB429;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-comment"># &#xB530;&#xB77C;&#xC11C; &#xB2E4;&#xC74C;&#xC740; ls &#xBA85;&#xB839;&#xC758; &#xD604;&#xC7AC; fd &#xB97C; &#xC870;&#xD68C;&#xD558;&#xB294; &#xAC83;&#xACFC; &#xAC19;&#xC2B5;&#xB2C8;&#xB2E4;.</span>
$ ls <span class="hljs-operator">-l</span> /dev/fd/     <span class="hljs-comment"># &#xB610;&#xB294; ls -l /proc/self/fd/</span>
total <span class="hljs-number">0</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">19</span>:<span class="hljs-number">09</span> <span class="hljs-number">0</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">19</span>:<span class="hljs-number">09</span> <span class="hljs-number">1</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">19</span>:<span class="hljs-number">09</span> <span class="hljs-number">2</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lr-x------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">19</span>:<span class="hljs-number">09</span> <span class="hljs-number">3</span> -&gt; /proc/<span class="hljs-number">8300</span>/fd/  <span class="hljs-comment"># ls &#xBA85;&#xB839; PID</span>

<span class="hljs-comment"># parent process &#xC758; FD &#xC124;&#xC815;&#xC740; child process &#xC5D0;&#xAC8C; &#xC0C1;&#xC18D;&#xB418;&#xBBC0;&#xB85C;</span>
<span class="hljs-comment"># &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; shell &#xC5D0;&#xC11C; &#xC124;&#xC815;&#xD55C; FD &#xAC12;&#xC740; `ls -l /dev/fd/` &#xCD9C;&#xB825;&#xC5D0;&#xB3C4; &#xB098;&#xD0C0;&#xB0A9;&#xB2C8;&#xB2E4;.</span>
$ <span class="hljs-built_in">exec</span> <span class="hljs-number">9</span>&lt;&gt; /dev/null

$ ls <span class="hljs-operator">-l</span> /proc/$$/fd/
total <span class="hljs-number">0</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">02</span> <span class="hljs-number">0</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">02</span> <span class="hljs-number">1</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">02</span> <span class="hljs-number">2</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">02</span> <span class="hljs-number">255</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">03</span> <span class="hljs-number">9</span> -&gt; /dev/null    &lt;--- <span class="hljs-number">9</span> &#xBC88;

<span class="hljs-comment"># parent process &#xC778; bash shell &#xC5D0;&#xC11C; &#xC124;&#xC815;&#xD55C; FD &#xAC12;&#xC774; &#xC0C1;&#xC18D;&#xB418;&#xC5B4; ls &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC5D0;&#xC11C;&#xB3C4; &#xBCF4;&#xC778;&#xB2E4;.</span>
$ ls <span class="hljs-operator">-l</span> /dev/fd/
total <span class="hljs-number">0</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">03</span> <span class="hljs-number">0</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">03</span> <span class="hljs-number">1</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">03</span> <span class="hljs-number">2</span> -&gt; /dev/pts/<span class="hljs-number">7</span>
lr-x------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">03</span> <span class="hljs-number">3</span> -&gt; /proc/<span class="hljs-number">20976</span>/fd/
lrwx------ <span class="hljs-number">1</span> mug896 mug896 <span class="hljs-number">64</span> <span class="hljs-number">2020</span>-<span class="hljs-number">03</span>-<span class="hljs-number">20</span> <span class="hljs-number">21</span>:<span class="hljs-number">03</span> <span class="hljs-number">9</span> -&gt; /dev/null    &lt;--- <span class="hljs-number">9</span> &#xBC88;
</code></pre>
<p>/proc &#xAC00; &#xAC00;&#xC9C0;&#xB294; &#xB610; &#xD55C;&#xAC00;&#xC9C0; &#xAE30;&#xB2A5;&#xC740; &#xD30C;&#xC77C; &#xC2DC;&#xC2A4;&#xD15C;&#xC744; &#xD1B5;&#xD574; &#xC9C1;&#xC811; &#xCEE4;&#xB110;&#xC758; &#xC635;&#xC158; &#xC124;&#xC815;&#xC744; &#xBCC0;&#xACBD;&#xD560;&#xC218; &#xC788;&#xB2E4;&#xB294; &#xAC83;&#xC785;&#xB2C8;&#xB2E4;.
&#xD558;&#xC9C0;&#xB9CC; &#xC124;&#xC815;&#xC774; &#xC800;&#xC7A5;&#xB418;&#xB294; &#xAC83;&#xC740; &#xC544;&#xB2C8;&#xBBC0;&#xB85C;  &#xC2DC;&#xC2A4;&#xD15C;&#xC744; &#xB2E4;&#xC2DC; &#xC2DC;&#xC791;&#xD558;&#xBA74; &#xAE30;&#xC874; &#xAC12;&#xC73C;&#xB85C; &#xB3CC;&#xC544;&#xAC11;&#xB2C8;&#xB2E4;.
&#xB2E4;&#xC74C;&#xC740; icmp echo &#xC640; &#xAD00;&#xB828;&#xB41C; &#xC635;&#xC158; &#xC124;&#xC815;&#xC744; /proc &#xB97C; &#xD1B5;&#xD574;&#xC11C; &#xD558;&#xB294; &#xC608;&#xC785;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># icmp_echo_ignore_all &#xC740; ping &#xBA85;&#xB839;&#xC5D0; &#xB300;&#xD55C; &#xC751;&#xB2F5; &#xC5EC;&#xBD80;&#xB97C; &#xC124;&#xC815;&#xD558;&#xB294; &#xC635;&#xC158;&#xC785;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-comment"># &#xAC12;&#xC774; 0 &#xC77C; &#xACBD;&#xC6B0;&#xB294; OFF &#xB97C;, 1 &#xC740; ON &#xC744; &#xB098;&#xD0C0;&#xB0C5;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-comment"># www.naver.com, www.daum.net &#xAC19;&#xC740; &#xACBD;&#xC6B0; ping &#xC744; &#xD588;&#xC744;&#xB54C; &#xC751;&#xB2F5;&#xC744; &#xBCFC;&#xC218;&#xAC00; &#xC5C6;&#xC73C;&#xBBC0;&#xB85C;</span>
<span class="hljs-comment"># icmp_echo_ignore_all &#xAC12;&#xC774; 1 &#xB85C; &#xC124;&#xC815;&#xB418;&#xC5B4; &#xC788;&#xB2E4;&#xACE0; &#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</span>

$ cat /proc/sys/net/ipv4/icmp_<span class="hljs-built_in">echo</span>_ignore_all 
<span class="hljs-number">0</span>

$ sudo sh -c <span class="hljs-string">&apos;echo 1 &gt; /proc/sys/net/ipv4/icmp_echo_ignore_all&apos;</span>

$ cat /proc/sys/net/ipv4/icmp_<span class="hljs-built_in">echo</span>_ignore_all 
<span class="hljs-number">1</span>

-------------------------------------------------------------
<span class="hljs-comment"># &#xB2E4;&#xC74C;&#xC740; sysctl &#xBA85;&#xB839;&#xC744; &#xC774;&#xC6A9;&#xD55C; &#xC124;&#xC815; &#xBC29;&#xBC95;&#xC785;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-comment"># /proc/sys/ &#xB97C; &#xC81C;&#xC678;&#xD558;&#xACE0; &apos;/&apos; &#xB97C; &apos;.&apos; &#xB85C; &#xBCC0;&#xACBD;&#xD558;&#xC5EC; &#xC0AC;&#xC6A9;&#xD558;&#xBA74; &#xB429;&#xB2C8;&#xB2E4;.</span>
$ sysctl net.ipv4.icmp_<span class="hljs-built_in">echo</span>_ignore_all 
net.ipv4.icmp_<span class="hljs-built_in">echo</span>_ignore_all = <span class="hljs-number">0</span>

$ sudo sysctl -w net.ipv4.icmp_<span class="hljs-built_in">echo</span>_ignore_all=<span class="hljs-number">1</span>
net.ipv4.icmp_<span class="hljs-built_in">echo</span>_ignore_all = <span class="hljs-number">1</span>

$ sysctl net.ipv4.icmp_<span class="hljs-built_in">echo</span>_ignore_all 
net.ipv4.icmp_<span class="hljs-built_in">echo</span>_ignore_all = <span class="hljs-number">1</span>

<span class="hljs-comment"># &#xC7AC;&#xBD80;&#xD305; &#xD6C4;&#xC5D0;&#xB3C4; &#xC801;&#xC6A9;&#xB418;&#xAC8C; &#xD558;&#xB824;&#xBA74; &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; /etc/sysctl.conf &#xD30C;&#xC77C;&#xC5D0; &#xCD94;&#xAC00;&#xD569;&#xB2C8;&#xB2E4;.</span>
$ <span class="hljs-built_in">echo</span> net.ipv4.icmp_<span class="hljs-built_in">echo</span>_ignore_all = <span class="hljs-number">1</span> | sudo tee <span class="hljs-operator">-a</span> /etc/sysctl.conf
</code></pre>
<blockquote>
<p>/proc &#xB514;&#xB809;&#xD1A0;&#xB9AC; &#xAD6C;&#xC870;&#xC5D0; &#xB300;&#xD55C; &#xC790;&#xC138;&#xD55C; &#xC124;&#xBA85;&#xC740; <code>man 5 proc</code> &#xB85C; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.<br>&#xC2DC;&#xC2A4;&#xD15C; &#xC804;&#xCCB4; &#xB514;&#xB809;&#xD1A0;&#xB9AC; &#xAD6C;&#xC870;&#xC5D0; &#xB300;&#xD55C; &#xC124;&#xBA85;&#xC740; <code>man 7 hier</code> &#xC785;&#xB2C8;&#xB2E4;.</p>
</blockquote>
<h1 id="sys">/sys</h1>
<p>/sys &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB294; /proc &#xC774;&#xD6C4;&#xC5D0; &#xC0DD;&#xAE34; &#xAC00;&#xC0C1; &#xD30C;&#xC77C; &#xC2DC;&#xC2A4;&#xD15C;&#xC785;&#xB2C8;&#xB2E4;.
&#xC6D0;&#xB798; /proc &#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xC815;&#xBCF4;&#xC640; ps, top, free &#xAC19;&#xC740; &#xBA87;&#xBA87; &#xC2DC;&#xC2A4;&#xD15C; &#xC720;&#xD2F8;&#xB9AC;&#xD2F0;&#xAC00; &#xC0AC;&#xC6A9;&#xD558;&#xB294;
&#xC815;&#xBCF4;&#xB97C; &#xC81C;&#xACF5;&#xD558;&#xB294; &#xAC8C; &#xBAA9;&#xC801;&#xC73C;&#xC600;&#xC73C;&#xB098; &#xC0AC;&#xC6A9;&#xC0C1;&#xC758; &#xC774;&#xC810;&#xC73C;&#xB85C; &#xC778;&#xD574; &#xBB34;&#xC791;&#xC704;&#xB85C; &#xC2DC;&#xC2A4;&#xD15C; &#xAD00;&#xB828; &#xC815;&#xBCF4;&#xB97C;
&#xC81C;&#xACF5;&#xD558;&#xB2E4; &#xBCF4;&#xB2C8; &#xC77C;&#xC885;&#xC758; dumping ground &#xAC00; &#xB418;&#xC5B4;&#xC11C; &#xB098;&#xC911;&#xC5D0; device, system &#xAD00;&#xB828; &#xC815;&#xBCF4;&#xB97C;
&#xC880; &#xB354; &#xAD6C;&#xC870;&#xC801;&#xC73C;&#xB85C; &#xC81C;&#xACF5;&#xD558;&#xAE30; &#xC704;&#xD574; &#xB9CC;&#xB4E0; &#xAC83;&#xC774; /sys &#xB514;&#xB809;&#xD1A0;&#xB9AC; &#xC785;&#xB2C8;&#xB2E4;.
&#xAE30;&#xC874; legacy &#xC2DC;&#xC2A4;&#xD15C; &#xC815;&#xBCF4;&#xB294; &#xC544;&#xC9C1; /proc &#xB97C; &#xD1B5;&#xD574;&#xC11C; &#xC811;&#xADFC;&#xD560; &#xC218; &#xC788;&#xC73C;&#xB098;
&#xC0C8;&#xB85C; &#xCD94;&#xAC00;&#xB418;&#xB294; device, system &#xAD00;&#xB828; &#xC815;&#xBCF4;&#xB294; /sys &#xB97C; &#xD1B5;&#xD574;&#xC11C; &#xC81C;&#xACF5;&#xB429;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># /proc, /sys &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xC5D0; &#xC788;&#xB294; &#xD56D;&#xBAA9;&#xB4E4;&#xC740; &#xB300;&#xBD80;&#xBD84; cat &#xBA85;&#xB839;&#xC73C;&#xB85C; read &#xAC00; &#xAC00;&#xB2A5;&#xD569;&#xB2C8;&#xB2E4;.</span>
<span class="hljs-comment"># &#xB2E4;&#xC74C; &#xD568;&#xC218;&#xB294; &#xD2B9;&#xC815; &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xC5D0; &#xC874;&#xC7AC;&#xD558;&#xB294; &#xD56D;&#xBAA9;&#xB4E4;&#xC744; &#xC77C;&#xAD04; cat &#xCD9C;&#xB825;&#xD574; &#xC90D;&#xB2C8;&#xB2E4;. ( -r &#xC635;&#xC158;&#xC740; recursive )</span>

<span class="hljs-function"><span class="hljs-title">syscat</span></span>() {
    <span class="hljs-built_in">local</span> recursive=<span class="hljs-literal">false</span> file arg
    <span class="hljs-built_in">local</span> cmd=<span class="hljs-string">&apos;echo &quot;\e[36m[ {} ]\e[0m&quot;; \
               echo &quot;$(timeout 1 cat &quot;{}&quot; | tr -cd &quot;[[:print:]\t\n]&quot;)&quot;&apos;</span>
    <span class="hljs-keyword">for</span> arg; <span class="hljs-keyword">do</span> [ <span class="hljs-string">&quot;<span class="hljs-variable">$arg</span>&quot;</span> = <span class="hljs-string">&quot;-r&quot;</span> ] &amp;&amp; { recursive=<span class="hljs-literal">true</span>; <span class="hljs-built_in">break</span>; }; <span class="hljs-keyword">done</span>
    <span class="hljs-keyword">if</span> <span class="hljs-variable">$recursive</span>; <span class="hljs-keyword">then</span>
        <span class="hljs-keyword">for</span> arg <span class="hljs-keyword">do</span> <span class="hljs-built_in">shift</span>; [ <span class="hljs-string">&quot;<span class="hljs-variable">$arg</span>&quot;</span> = <span class="hljs-string">&quot;-r&quot;</span> ] &amp;&amp; <span class="hljs-built_in">continue</span>; <span class="hljs-built_in">set</span> -- <span class="hljs-string">&quot;<span class="hljs-variable">$@</span>&quot;</span> <span class="hljs-string">&quot;<span class="hljs-variable">$arg</span>&quot;</span>; <span class="hljs-keyword">done</span>
        sudo -E find <span class="hljs-string">&quot;<span class="hljs-variable">$@</span>&quot;</span> \( -path <span class="hljs-string">&quot;*/tracing&quot;</span> -o -path <span class="hljs-string">&quot;*/debug&quot;</span> \) -prune -o \
             ! -type d,l -exec sh -c <span class="hljs-string">&quot;<span class="hljs-variable">$cmd</span>&quot;</span> \; <span class="hljs-number">2</span>&gt; /dev/null
    <span class="hljs-keyword">else</span>
        <span class="hljs-built_in">test</span> <span class="hljs-variable">$#</span> = <span class="hljs-number">1</span> <span class="hljs-operator">-a</span> <span class="hljs-operator">-d</span> <span class="hljs-string">&quot;<span class="hljs-variable">$1</span>&quot;</span> &amp;&amp; <span class="hljs-built_in">set</span> -- <span class="hljs-string">&quot;<span class="hljs-variable">${1%/}</span>&quot;</span>/*
        <span class="hljs-keyword">for</span> file; <span class="hljs-keyword">do</span> <span class="hljs-built_in">test</span> <span class="hljs-operator">-f</span> <span class="hljs-string">&quot;<span class="hljs-variable">$file</span>&quot;</span> &amp;&amp;
            sudo -E find <span class="hljs-string">&quot;<span class="hljs-variable">$file</span>&quot;</span> -exec sh -c <span class="hljs-string">&quot;<span class="hljs-variable">$cmd</span>&quot;</span> \;
        <span class="hljs-keyword">done</span>
    <span class="hljs-keyword">fi</span>
}

<span class="hljs-comment"># &#xBE14;&#xB85D; &#xB514;&#xBC14;&#xC774;&#xC2A4;&#xC778; /dev/sda &#xB514;&#xC2A4;&#xD06C; &#xC815;&#xBCF4;&#xB97C; &#xCD9C;&#xB825;</span>
$ syscat /sys/block/sda/queue
. . .
[ minimum_io_size ]
<span class="hljs-number">512</span>
[ nr_zones ]
<span class="hljs-number">0</span>
[ write_same_max_bytes ]
<span class="hljs-number">0</span>
[ max_segments ]
<span class="hljs-number">168</span>
[ dax ]
<span class="hljs-number">0</span>
[ physical_block_size ]
<span class="hljs-number">512</span>
[ logical_block_size ]
<span class="hljs-number">512</span>
[ zone_append_max_bytes ]
<span class="hljs-number">0</span>
[ io_timeout ]
<span class="hljs-number">30000</span>
. . .
</code></pre>
<p>&#xB2E4;&#xC74C;&#xC740; /sys &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB97C; &#xC774;&#xC6A9;&#xD574;&#xC11C; &#xD604;&#xC7AC; &#xC0AC;&#xC6A9;&#xC911;&#xC778; cpu core &#xB97C; disable &#xD558;&#xB294; &#xC608;&#xC785;&#xB2C8;&#xB2E4;.
&#xB124;&#xD2B8;&#xC6CC;&#xD06C; &#xCE74;&#xB4DC;&#xB098; &#xB9C8;&#xC6B0;&#xC2A4; &#xC778;&#xD130;&#xB7FD;&#xD2B8;&#xB97C; &#xCC98;&#xB9AC; &#xC911;&#xC778; core &#xB97C; disable &#xD558;&#xBA74;
&#xD574;&#xB2F9; &#xCC98;&#xB9AC;&#xAC00; &#xB2E4;&#xB978; core &#xB85C; &#xC62E;&#xACA8;&#xAC00;&#xB294; &#xAC83;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;. 
&#xB610;&#xD55C; cpu0 &#xC740; disable &#xD560; &#xC218; &#xC5C6;&#xC2B5;&#xB2C8;&#xB2E4;
( &#xAE30;&#xBCF8;&#xC801;&#xC73C;&#xB85C; APIC &#xAC00; &#xC778;&#xD130;&#xB7FD;&#xD2B8;&#xB97C; cpu0 &#xC73C;&#xB85C; &#xC804;&#xB2EC;&#xD569;&#xB2C8;&#xB2E4;. )
[ <a href="process_state_codes.html#interrupt">interrupt &#xC870;&#xD68C;&#xBC29;&#xBC95;</a> ]</p>
<pre><code class="lang-bash">$ ls /sys/devices/system/cpu                           
cpu0/  cpu3/  cpu6/     cpuidle/       microcode/  vulnerabilities/  modalias  possible
cpu1/  cpu4/  cpu7/     hotplug/       power/      isolated          offline   present
cpu2/  cpu5/  cpufreq/  intel_pstate/  smt/        kernel_max        online    uevent

<span class="hljs-comment"># online &#xAC12;&#xC774; 1 &#xC774;&#xBA74; &#xD604;&#xC7AC; &#xC0AC;&#xC6A9;&#xC911;&#xC778; &#xC0C1;&#xD0DC;</span>
$ cat /sys/devices/system/cpu/cpu6/online
<span class="hljs-number">1</span>

<span class="hljs-comment"># 0 &#xC73C;&#xB85C; &#xC124;&#xC815;&#xD558;&#xC5EC; cpu6 &#xC744; offline &#xC0C1;&#xD0DC;&#xB85C; &#xB9CC;&#xB4ED;&#xB2C8;&#xB2E4;.</span>
$ <span class="hljs-built_in">echo</span> <span class="hljs-number">0</span> | sudo tee /sys/devices/system/cpu/cpu6/online
<span class="hljs-number">0</span>

$ grep processor /proc/cpuinfo
processor       : <span class="hljs-number">0</span>
processor       : <span class="hljs-number">1</span>
processor       : <span class="hljs-number">2</span>
processor       : <span class="hljs-number">3</span>
processor       : <span class="hljs-number">4</span>
processor       : <span class="hljs-number">5</span>       &lt;------- processor <span class="hljs-number">6</span> &#xBC88;&#xC774; &#xC81C;&#xAC70;&#xB428;
processor       : <span class="hljs-number">7</span>
</code></pre>
<h1 id="dev">/dev</h1>
<p>/proc &#xAC00; &#xCEE4;&#xB110;&#xC774; &#xAC00;&#xC9C0;&#xACE0; &#xC788;&#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC640; &#xC2DC;&#xC2A4;&#xD15C; &#xAD00;&#xB828; &#xC815;&#xBCF4;&#xB97C; &#xC0AC;&#xC6A9;&#xC790;&#xC5D0;&#xAC8C; &#xC81C;&#xACF5;&#xD558;&#xB294;&#xAC8C; &#xBAA9;&#xC801;&#xC774;&#xB77C;&#xBA74;
&#xC5B4;&#xB5BB;&#xAC8C; &#xD558;&#xBA74; &#xCEE4;&#xB110;&#xC774; &#xAD00;&#xB9AC;&#xD558;&#xB294; &#xC7A5;&#xCE58;&#xB4E4;&#xC744; &#xC0AC;&#xC6A9;&#xC790;&#xC5D0;&#xAC8C; &#xC81C;&#xACF5;&#xD560;&#xC218; &#xC788;&#xC744;&#xAE4C;&#xC5D0; &#xB300;&#xD55C; &#xD574;&#xACB0;&#xCC45;&#xC774; 
/dev &#xB514;&#xB809;&#xD1A0;&#xB9AC; &#xC785;&#xB2C8;&#xB2E4;.
&#xC774; &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB294; /proc &#xC640; &#xB2EC;&#xB9AC; &#xAC00;&#xC0C1;&#xC758; &#xD30C;&#xC77C; &#xC2DC;&#xC2A4;&#xD15C;&#xC774; &#xC544;&#xB2C8;&#xACE0; 
mknod &#xBA85;&#xB839;&#xC73C;&#xB85C; &#xC9C1;&#xC811; &#xC7A5;&#xCE58;&#xD30C;&#xC77C;&#xC744; &#xB9CC;&#xB4ED;&#xB2C8;&#xB2E4;.
&#xC0DD;&#xC131;&#xB41C; &#xC7A5;&#xCE58;&#xD30C;&#xC77C;&#xC740; &#xAF2D; /dev &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xC5D0; &#xC704;&#xCE58;&#xD560; &#xD544;&#xC694;&#xB294; &#xC5C6;&#xACE0;, &#xC77C;&#xBC18; &#xD30C;&#xC77C;&#xB4E4;&#xACFC; &#xB611;&#xAC19;&#xC774;
mv, rm, cp -R, rename &#xC744; &#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xB610;&#xD55C; &#xC0AC;&#xC6A9;&#xC790; &#xD504;&#xB85C;&#xADF8;&#xB7A8;&#xC5D0;&#xC11C; &#xC7A5;&#xCE58;&#xD30C;&#xC77C;&#xC744; &#xC0AC;&#xC6A9;&#xD558;&#xB294; &#xBC29;&#xBC95;&#xB3C4; &#xC77C;&#xBC18; &#xD30C;&#xC77C;&#xACFC; &#xAC19;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<p>/dev &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB97C; ls  &#xD574; &#xBCF4;&#xBA74; &#xD30C;&#xC77C; &#xC0AC;&#xC774;&#xC988; &#xB300;&#xC2E0;&#xC5D0; &#xB450;&#xAC1C;&#xC758; &#xC22B;&#xC790;&#xAC00; <code>,</code> &#xB85C;
&#xAD6C;&#xBD84;&#xB418;&#xC5B4; &#xD45C;&#xC2DC;&#xB418;&#xB294; &#xAC83;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xB294;&#xB370;&#xC694; &#xAC01;&#xAC01; major number, minor number &#xB77C;&#xACE0; &#xD569;&#xB2C8;&#xB2E4;.
&#xD30C;&#xC77C;&#xC744; &#xC624;&#xD508; &#xD588;&#xC744;&#xB54C; &#xC774; &#xBC88;&#xD638;&#xB85C; &#xCEE4;&#xB110;&#xC740; &#xC5B4;&#xB5A4; &#xC7A5;&#xCE58; &#xB4DC;&#xB77C;&#xC774;&#xBC84;&#xB97C; &#xC0AC;&#xC6A9;&#xD574;&#xC57C; &#xB420;&#xC9C0; &#xC54C; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB7EC;&#xB2C8;&#xAE4C; &#xC7A5;&#xCE58;&#xD30C;&#xC77C;&#xC758; &#xC774;&#xB984;&#xC740; &#xC2E4;&#xC9C8;&#xC801;&#xC73C;&#xB85C; &#xC911;&#xC694;&#xD558;&#xC9C0; &#xC54A;&#xACE0; &#xC784;&#xC758;&#xB85C; &#xB9CC;&#xB4E4;&#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;. 
&#xD130;&#xBBF8;&#xB110; &#xD504;&#xB85C;&#xADF8;&#xB7A8;&#xC744; &#xBA87;&#xAC1C; &#xC624;&#xD508;&#xD55C;&#xB4A4; <code>ls -l /dev/pts/</code> &#xD574;&#xBCF4;&#xBA74; &#xC7A5;&#xCE58; &#xD30C;&#xC77C;&#xB4E4;&#xC774; &#xC0C8;&#xB85C; &#xC0DD;&#xC131;&#xB41C;&#xAC78; &#xBCFC; &#xC218; &#xC788;&#xB294;&#xB370;
minor number &#xAC00; &#xBAA8;&#xB450; &#xB2E4;&#xB978; &#xAC83;&#xC744; &#xC54C; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
major number &#xAC00; &#xC7A5;&#xCE58; &#xB4DC;&#xB77C;&#xC774;&#xBC84;&#xB97C; &#xB098;&#xD0C0;&#xB0B8;&#xB2E4;&#xBA74; minor number &#xB294; &#xC774;&#xB807;&#xAC8C;
&#xAC19;&#xC740; &#xC7A5;&#xCE58; &#xB4DC;&#xB77C;&#xC774;&#xBC84;&#xB97C; &#xC0AC;&#xC6A9;&#xD558;&#xC9C0;&#xB9CC; &#xAD6C;&#xBD84;&#xD558;&#xAE30; &#xC704;&#xD55C; &#xC6A9;&#xB3C4;&#xB85C; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.</p>
<p>&#xCEF4;&#xD4E8;&#xD130;&#xC5D0;&#xC11C; &#xC0AC;&#xC6A9;&#xB418;&#xB294; &#xC7A5;&#xCE58;&#xB4E4;&#xC744; &#xB450;&#xAC00;&#xC9C0;&#xB85C; &#xBD84;&#xB958;&#xD574; &#xBCFC; &#xC218; &#xC788;&#xB294;&#xB370;&#xC694;.
&#xB370;&#xC774;&#xD130;&#xC5D0; &#xC811;&#xADFC;&#xD560;&#xB54C; random access &#xB97C; &#xD560; &#xC218; &#xC788;&#xB294; &#xC7A5;&#xCE58;&#xC640; &#xADF8;&#xB807;&#xC9C0; &#xC54A;&#xC740; &#xC7A5;&#xCE58;&#xC785;&#xB2C8;&#xB2E4;.
&#xCCAB;&#xBC88;&#xC9F8;&#xC758; &#xACBD;&#xC6B0;&#xB97C; block device &#xB77C;&#xACE0; &#xD558;&#xACE0; &#xB514;&#xB809;&#xD1A0;&#xB9AC; &#xD37C;&#xBBF8;&#xC158;&#xC758; &#xCCAB;&#xBC88;&#xC9F8; &#xBB38;&#xC790;&#xAC00; <code>b</code> &#xB85C; &#xD45C;&#xC2DC;&#xB429;&#xB2C8;&#xB2E4;.
&#xB450;&#xBC88;&#xC9F8;&#xB294; character device &#xB77C;&#xACE0; &#xD558;&#xBA70; <code>c</code> &#xB85C; &#xD45C;&#xC2DC;&#xB429;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash"><span class="hljs-comment"># block device &#xB9CC; &#xCD9C;&#xB825;</span>
$ find /dev -type b -exec ls <span class="hljs-operator">-l</span> {} \;

<span class="hljs-comment"># character device &#xB9CC; &#xCD9C;&#xB825;</span>
$ find /dev -type c -exec ls <span class="hljs-operator">-l</span> {} \;
</code></pre>
<h4 id="character-device">Character device</h4>
<p>character device &#xB294; &#xB370;&#xC774;&#xD130;&#xAC00; 1 byte &#xD06C;&#xAE30;&#xC758; character by character &#xB85C; &#xC804;&#xB2EC;&#xB418;&#xACE0;
random access &#xB97C; &#xD560; &#xC218; &#xC5C6;&#xB294; &#xC7A5;&#xCE58;&#xC785;&#xB2C8;&#xB2E4;.
&#xB370;&#xC774;&#xD130;&#xAC00; &#xC804;&#xB2EC;&#xB420; &#xB54C; &#xCEE4;&#xB110;&#xC774; &#xC0AC;&#xC6A9;&#xD558;&#xB294; &#xBC84;&#xD37C;&#xB97C; &#xAC70;&#xCE58;&#xC9C0; &#xC54A;&#xACE0; &#xBC14;&#xB85C; &#xC7A5;&#xCE58;&#xC5D0; &#xC804;&#xB2EC;&#xB429;&#xB2C8;&#xB2E4;.
&#xD0A4;&#xBCF4;&#xB4DC;&#xD0A4;&#xB97C; &#xD558;&#xB098; &#xB204;&#xB974;&#xBA74; &#xBC14;&#xB85C; &#xBB38;&#xC790;&#xAC00; &#xD45C;&#xC2DC;&#xB418;&#xACE0; &#xB9C8;&#xC6B0;&#xC2A4;&#xB97C; &#xC6C0;&#xC9C1;&#xC774;&#xBA74; &#xBC14;&#xB85C; &#xD3EC;&#xC778;&#xD130;&#xAC00; &#xC6C0;&#xC9C1;&#xC774;&#xB294;&#xB370; &#xBAA8;&#xB450; character device &#xC785;&#xB2C8;&#xB2E4;.
&#xC0AC;&#xC2E4; &#xB514;&#xC2A4;&#xD06C;&#xC640; &#xAD00;&#xB828;&#xB41C; &#xC7A5;&#xCE58;&#xB97C; &#xC81C;&#xC678;&#xD558;&#xACE0; &#xB300;&#xBD80;&#xBD84;&#xC758; &#xC7A5;&#xCE58;&#xAC00; character device &#xC785;&#xB2C8;&#xB2E4;.</p>
<ul>
<li>&#xB9C8;&#xC6B0;&#xC2A4; : /dev/input/ </li>
<li>&#xADF8;&#xB798;&#xD53D; : /dev/dri/  </li>
<li>&#xC0AC;&#xC6B4;&#xB4DC; : /dev/snd/  </li>
<li>&#xD130;&#xBBF8;&#xB110; : /dev/tty*, /dev/pts/*</li>
</ul>
<h4 id="devtty"><a href="tty.html">/dev/tty</a></h4>
<p>/dev/tty &#xB294; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xC758; controlling terminal &#xACFC; &#xB3D9;&#xC77C;&#xD569;&#xB2C8;&#xB2E4;.
&#xB2E4;&#xC2DC;&#xB9D0;&#xD574; &#xD604;&#xC7AC; ctty &#xAC00; /dev/pts/1 &#xC774;&#xB77C;&#xBA74; /dev/tty &#xB3C4; /dev/pts/1 &#xB77C;&#xACE0; &#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xC5B4;&#xB5A4; &#xD504;&#xB85C;&#xC138;&#xC2A4;&#xAC00; /dev/tty &#xB97C; open &#xD558;&#xB294;&#xB370; &#xC2E4;&#xD328;&#xD558;&#xC600;&#xB2E4;&#xBA74; ctty &#xB97C; &#xAC16;&#xACE0;&#xC788;&#xC9C0; &#xC54A;&#xB2E4;&#xACE0; &#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
standard stream &#xC774; &#xBAA8;&#xB450; redirect &#xB418;&#xC5B4;&#xC788;&#xB2E4;&#xACE0; &#xD558;&#xB354;&#xB77C;&#xB3C4; /dev/tty &#xB85C; &#xCD9C;&#xB825;&#xD558;&#xBA74; &#xD130;&#xBBF8;&#xB110;&#xB85C; &#xCD9C;&#xB825;&#xD560; &#xC218; &#xC788;&#xACE0;
&#xB610;&#xD55C; /dev/tty &#xB97C; &#xC774;&#xC6A9;&#xD574; &#xD130;&#xBBF8;&#xB110;&#xB85C;&#xBD80;&#xD130; &#xC785;&#xB825;&#xC744; &#xBC1B;&#xC744; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<h4 id="block-device">Block device</h4>
<p>&#xD558;&#xB4DC;&#xB514;&#xC2A4;&#xD06C;, CD-ROM, USB &#xBA54;&#xBAA8;&#xB9AC; &#xAC19;&#xC774; random access &#xB97C; &#xD560; &#xC218; &#xC788;&#xB294; &#xC7A5;&#xCE58;&#xAC00; block device &#xC5D0; &#xD574;&#xB2F9;&#xD569;&#xB2C8;&#xB2E4;.
block device &#xB294; &#xCEE4;&#xB110;&#xC774; &#xAD00;&#xB9AC;&#xD558;&#xB294; &#xBC84;&#xD37C;&#xB97C; &#xC774;&#xC6A9;&#xD558;&#xACE0; block &#xB2E8;&#xC704;&#xB85C; ( &#xBCF4;&#xD1B5; 512 bytes )  &#xB370;&#xC774;&#xD130;&#xAC00; &#xC804;&#xB2EC;&#xB429;&#xB2C8;&#xB2E4;.
character device &#xC640; block device &#xB294; &#xB0B4;&#xBD80;&#xC801;&#xC73C;&#xB85C; &#xCC98;&#xB9AC;&#xD558;&#xB294; &#xBC29;&#xC2DD;&#xC774; &#xB2E4;&#xB974;&#xAE30; &#xB54C;&#xBB38;&#xC5D0;
&#xD558;&#xB098;&#xC758; &#xBB3C;&#xB9AC; &#xC7A5;&#xCE58;&#xC5D0; &#xB450; &#xAC00;&#xC9C0;&#xC758; &#xC7A5;&#xCE58; &#xD30C;&#xC77C;&#xC744; &#xC81C;&#xACF5;&#xD558;&#xAE30;&#xB3C4; &#xD569;&#xB2C8;&#xB2E4;.
&#xB610;&#xD55C; &#xBC84;&#xD37C; &#xCE90;&#xC2DC;&#xB97C; &#xC774;&#xC6A9;&#xD558;&#xB294; &#xAC83;&#xC774; &#xC2E4;&#xC81C; &#xB370;&#xC774;&#xD130;&#xAC00; &#xC7A5;&#xCE58;&#xC5D0; &#xC4F0;&#xC5EC;&#xC9C0;&#xB294; &#xC21C;&#xC11C;&#xB098; &#xAC00;&#xC2DC;&#xC131;&#xC5D0; &#xC601;&#xD5A5;&#xC744; &#xC904; &#xC218; &#xC788;&#xB2E4;&#xACE0; &#xD558;&#xC5EC;
&#xC544;&#xC608; character device &#xB9CC; &#xC81C;&#xACF5;&#xD558;&#xB294; <a href="https://www.freebsd.org/doc/en/books/arch-handbook/driverbasics-block.html" target="_blank">OS</a>
&#xB3C4; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">/dev/sda[&#xBC88;&#xD638;]     <span class="hljs-comment"># &#xD558;&#xB4DC;&#xB514;&#xC2A4;&#xD06C;</span>

/dev/ram[&#xBC88;&#xD638;]     <span class="hljs-comment"># ramdisk &#xB97C; &#xB9CC;&#xB4E4;&#xB54C; &#xC0AC;&#xC6A9;</span>

/dev/loop[&#xBC88;&#xD638;]    <span class="hljs-comment"># iso &#xC774;&#xBBF8;&#xC9C0; &#xD30C;&#xC77C;&#xC744; &#xB9C8;&#xC6B4;&#xD2B8; &#xD560;&#xB54C; &#xC0AC;&#xC6A9;</span>
</code></pre>
<h4 id="pseudo-devices">Pseudo devices</h4>
<p>Pseudo devices &#xB294; &#xC2E4;&#xC81C; &#xBB3C;&#xB9AC; &#xC7A5;&#xCE58;&#xC5D0; &#xC5F0;&#xACB0;&#xB418;&#xC5B4; &#xC788;&#xB294;&#xAC83;&#xC740; &#xC544;&#xB2C8;&#xACE0;
&#xCEE4;&#xB110;&#xC5D0;&#xC11C; &#xC81C;&#xACF5;&#xD558;&#xB294; &#xD558;&#xB098;&#xC758; &#xAE30;&#xB2A5;&#xC73C;&#xB85C; &#xBCF4;&#xBA74; &#xB418;&#xACA0;&#xC2B5;&#xB2C8;&#xB2E4;.
<code>/dev/null</code> &#xC740; shell script &#xC5D0;&#xC11C;&#xB3C4; &#xB9CE;&#xC774; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;.</p>
<ul>
<li><code>/dev/null</code> : &#xC774; &#xC7A5;&#xCE58;&#xC5D0; &#xC4F0;&#xAE30;&#xB97C; &#xD560;&#xACBD;&#xC6B0; &#xC785;&#xB825;&#xB418;&#xB294; &#xB370;&#xC774;&#xD130;&#xB294; &#xBAA8;&#xB450; &#xC0AC;&#xB77C;&#xC9C0;&#xACE0; &#xC4F0;&#xAE30; &#xC131;&#xACF5;&#xC774; &#xBC18;&#xD658;&#xB429;&#xB2C8;&#xB2E4;.
&#xBE14;&#xB799;&#xD640;&#xACFC; &#xAC19;&#xC740; &#xC874;&#xC7AC;&#xC785;&#xB2C8;&#xB2E4;. &#xBCF4;&#xD1B5; &#xBA85;&#xB839; &#xC2E4;&#xD589;&#xC2DC; &#xC6D0;&#xD558;&#xB294;&#xC9C0; &#xC54A;&#xB294; data stream &#xC744; &#xC5EC;&#xAE30;&#xB85C; &#xBCF4;&#xB0C5;&#xB2C8;&#xB2E4;.
&#xC77D;&#xC744;&#xACBD;&#xC6B0; End-Of-File &#xC0C1;&#xD0DC;&#xB97C; &#xB9AC;&#xD134;&#xD569;&#xB2C8;&#xB2E4;.</li>
</ul>
<pre><code>$ cpp -dM /dev/null                 # End-Of-File: &#xBAA8;&#xB4E0; predefined macros &#xB97C; &#xCD9C;&#xB825;
#define __SSP_STRONG__ 3
#define __DBL_MIN_EXP__ (-1021)
#define __FLT32X_MAX_EXP__ 1024
. . .
</code></pre><ul>
<li><code>/dev/zero</code> : &#xC77D;&#xC744;&#xACBD;&#xC6B0; &#xC5F0;&#xC18D;&#xB41C; NUL &#xBB38;&#xC790;&#xAC00; &#xC81C;&#xACF5;&#xB418;&#xBBC0;&#xB85C; &#xBCF4;&#xD1B5; &#xB370;&#xC774;&#xD130; &#xC2A4;&#xD1A0;&#xB9AC;&#xC9C0;&#xB97C; &#xCD08;&#xAE30;&#xD654; &#xD560;&#xB54C; &#xC0AC;&#xC6A9;&#xD569;&#xB2C8;&#xB2E4;.
&#xC4F0;&#xAE30;&#xB97C; &#xD560;&#xACBD;&#xC6B0; /dev/null &#xACFC;&#xAC19;&#xC774; &#xBE14;&#xB799;&#xD640; &#xC5ED;&#xD560;&#xC744; &#xD569;&#xB2C8;&#xB2E4;.</li>
</ul>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xB2E4;&#xC74C;&#xACFC; &#xAC19;&#xC774; &#xD558;&#xBA74; &#xD574;&#xB2F9; &#xD30C;&#xD2F0;&#xC158; &#xB370;&#xC774;&#xD130;&#xAC00; &#xC2E4;&#xC9C8;&#xC801;&#xC73C;&#xB85C; &#xBAA8;&#xB450; &#xC0AD;&#xC81C;&#xB418;&#xC5B4; &#xBCF5;&#xAD6C;&#xD560;&#xC218; &#xC5C6;&#xAC8C; &#xB429;&#xB2C8;&#xB2E4;.</span>

$ dd <span class="hljs-keyword">if</span>=/dev/zero of=/dev/&lt;destination partition&gt;
</code></pre>
<ul>
<li><p><code>/dev/urandom</code> : &#xC5F0;&#xC18D;&#xB41C; pseudo random numbers &#xB97C; &#xC81C;&#xACF5;&#xD569;&#xB2C8;&#xB2E4;.</p>
</li>
<li><p><code>/dev/full</code> : &#xC774; &#xC7A5;&#xCE58;&#xC5D0; &#xC4F0;&#xAE30;&#xB97C; &#xD560;&#xACBD;&#xC6B0; &#xD56D;&#xC0C1; ENOSPC (No space left on device) error code &#xB97C; &#xBC18;&#xD658;&#xD569;&#xB2C8;&#xB2E4;.
&#xADF8;&#xB7EC;&#xBBC0;&#xB85C; &#xBCF4;&#xD1B5; &#xD504;&#xB85C;&#xADF8;&#xB7A8;&#xC5D0;&#xC11C; disk full &#xC0C1;&#xD0DC;&#xB97C; &#xD14C;&#xC2A4;&#xD2B8; &#xD560;&#xB54C; &#xC0AC;&#xC6A9;&#xB429;&#xB2C8;&#xB2E4;. 
&#xC77D;&#xC744;&#xACBD;&#xC6B0; &#xC5F0;&#xC18D;&#xB41C; NUL &#xBB38;&#xC790;&#xAC00; &#xC81C;&#xACF5;&#xB429;&#xB2C8;&#xB2E4;.</p>
</li>
</ul>
<pre><code class="lang-bash">$ <span class="hljs-built_in">echo</span> <span class="hljs-number">111</span> &gt; /dev/full
bash: <span class="hljs-built_in">echo</span>: write error: No space left on device

$ <span class="hljs-built_in">echo</span> $?
<span class="hljs-number">1</span>
</code></pre>
<h4 id="architectural-view-of-the-linux-file-system-components">Architectural view of the Linux file system components</h4>
<p><img src="images/linux_filesystem.png" alt=""></p>
<h1 id="quiz">Quiz</h1>
<p>&#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xC758; &#xAD8C;&#xD55C;&#xC774; <code>drwxrwxrwx</code> &#xC774;&#xBA74; &#xB204;&#xAD6C;&#xB098; &#xB4E4;&#xC5B4;&#xC640;&#xC11C; &#xD30C;&#xC77C;&#xC744; &#xC0DD;&#xC131;&#xD558;&#xACE0; &#xC4F8; &#xC218;&#xAC00; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xD558;&#xC9C0;&#xB9CC; &#xB2E4;&#xB978; &#xC0AC;&#xC6A9;&#xC790;&#xC758; &#xD30C;&#xC77C;&#xB3C4; &#xC0AD;&#xC81C;&#xD560; &#xC218;&#xAC00; &#xC788;&#xAE30; &#xB54C;&#xBB38;&#xC5D0; &#xC784;&#xC2DC; &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB97C; &#xB9CC;&#xB4E4; &#xB54C;&#xB294;
sticky bit &#xC744; &#xBD99;&#xC5EC;&#xC11C; &#xC0AD;&#xC81C;&#xB97C; &#xBC29;&#xC9C0;&#xD569;&#xB2C8;&#xB2E4;(<code>.......rwt</code>).
shell &#xC5D0;&#xC11C; &#xC784;&#xC2DC;&#xB85C; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xB294; &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xC5D0;&#xB294; <code>/tmp</code>, <code>/var/tmp</code>, <code>/dev/shm</code> &#xAC00; &#xC788;&#xB294;&#xB370;
&#xAC01;&#xAC01; &#xC5B4;&#xB5A4; &#xCC28;&#xC774;&#xAC00; &#xC788;&#xC744;&#xAE4C;&#xC694;?</p>
<pre><code class="lang-bash"><span class="hljs-comment"># &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xC5D0; &#xBAA8;&#xB450; sticky bit &#xC774; &#xC124;&#xC815;&#xB418;&#xC5B4; &#xC788;&#xC5B4;&#xC11C; &#xB2E4;&#xB978; &#xC0AC;&#xC6A9;&#xC790;&#xC758; &#xD30C;&#xC77C;&#xC740; &#xC0AD;&#xC81C;&#xD560; &#xC218; &#xC5C6;&#xB2E4;.</span>
$ ls -ld /tmp /var/tmp /dev/shm
drwxrwxrwt  <span class="hljs-number">2</span> root root   <span class="hljs-number">40</span> <span class="hljs-number">2019</span>-<span class="hljs-number">04</span>-<span class="hljs-number">20</span> <span class="hljs-number">18</span>:<span class="hljs-number">42</span> /dev/shm/
drwxrwxrwt <span class="hljs-number">18</span> root root <span class="hljs-number">4096</span> <span class="hljs-number">2019</span>-<span class="hljs-number">04</span>-<span class="hljs-number">20</span> <span class="hljs-number">18</span>:<span class="hljs-number">41</span> /tmp/
drwxrwxrwt  <span class="hljs-number">7</span> root root <span class="hljs-number">4096</span> <span class="hljs-number">2019</span>-<span class="hljs-number">04</span>-<span class="hljs-number">20</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span> /var/tmp/
</code></pre>
<p>&#xBA3C;&#xC800; <code>/tmp</code> &#xC640; <code>/var/tmp</code> &#xB294; disk &#xC5D0; &#xC874;&#xC7AC;&#xD558;&#xB294; &#xB514;&#xB809;&#xD1A0;&#xB9AC; &#xC785;&#xB2C8;&#xB2E4;.
&#xCC28;&#xC774;&#xC810;&#xC740; <code>/tmp</code> &#xB294; reboot &#xC774; &#xB418;&#xBA74; &#xB0B4;&#xC6A9;&#xC774; &#xC0AC;&#xB77C;&#xC9C0;&#xC9C0;&#xB9CC; <code>/var/tmp</code> &#xC758; &#xACBD;&#xC6B0;&#xB294; &#xC0AD;&#xC81C;&#xB418;&#xC9C0; &#xC54A;&#xACE0; &#xB0A8;&#xC544; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.
&#xB530;&#xB77C;&#xC11C; reboot &#xD6C4;&#xC5D0;&#xB3C4; &#xB370;&#xC774;&#xD130;&#xAC00; &#xBCF4;&#xC874;&#xB418;&#xC5B4;&#xC57C; &#xD560; &#xACBD;&#xC6B0;&#xB294; ( &#xC608;&#xB97C; &#xB4E4;&#xBA74; cache &#xB370;&#xC774;&#xD130; )
<code>/var/tmp</code> &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB97C; &#xC774;&#xC6A9;&#xD574;&#xC57C; &#xD569;&#xB2C8;&#xB2E4;.</p>
<p>&#xB9C8;&#xC6B4;&#xD2B8; &#xD560; &#xB54C; &#xD30C;&#xC77C;&#xC2DC;&#xC2A4;&#xD15C; &#xD0C0;&#xC785;&#xC73C;&#xB85C; <code>tmpfs</code> &#xC744; &#xC0AC;&#xC6A9;&#xD558;&#xBA74; &#xAC00;&#xC0C1;&#xC8FC;&#xC18C;&#xB97C; &#xC0AC;&#xC6A9;&#xD558;&#xB294; &#xBA54;&#xBAA8;&#xB9AC;&#xB85C; &#xB9C8;&#xC6B4;&#xD2B8;&#xAC00; &#xB429;&#xB2C8;&#xB2E4;.
<code>/dev/shm</code> &#xC758; &#xACBD;&#xC6B0; &#xBCF4;&#xD1B5; &#xBB3C;&#xB9AC; &#xBA54;&#xBAA8;&#xB9AC;&#xC758; 50% &#xD06C;&#xAE30;&#xB85C; &#xC124;&#xC815;&#xC774; &#xB418;&#xB294;&#xB370; ramdisk &#xAC19;&#xC774; &#xCC98;&#xC74C;&#xBD80;&#xD130; &#xC774; &#xD06C;&#xAE30;&#xAC00;
&#xBAA8;&#xB450; &#xC0AC;&#xC6A9;&#xB418;&#xB294; &#xAC83;&#xC774; &#xC544;&#xB2C8;&#xACE0; &#xAC00;&#xC0C1;&#xC8FC;&#xC18C; &#xC2DC;&#xC2A4;&#xD15C;&#xC744; &#xC774;&#xC6A9;&#xD574;&#xC11C; &#xD544;&#xC694;&#xD55C; &#xB9CC;&#xD07C;&#xB9CC; &#xC0AC;&#xC6A9;&#xD558;&#xAC8C; &#xB429;&#xB2C8;&#xB2E4;.
/dev/shm ( shared memory ) &#xC774;&#xB984;&#xC5D0;&#xC11C;&#xB3C4; &#xC54C; &#xC218; &#xC788;&#xB4EF;&#xC774; &#xD504;&#xB85C;&#xC138;&#xC2A4; &#xAC04;&#xC5D0; &#xBE60;&#xB978; &#xB370;&#xC774;&#xD130; &#xACF5;&#xC720;&#xAC00; 
&#xD544;&#xC694;&#xD560;&#xB54C; &#xC0AC;&#xC6A9;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.  &#xBA54;&#xBAA8;&#xB9AC;&#xC774;&#xBBC0;&#xB85C; reboot &#xD6C4;&#xC5D0;&#xB294; &#xC0AD;&#xC81C;&#xB429;&#xB2C8;&#xB2E4;.</p>
<pre><code class="lang-bash">$ df -h | grep tmpfs
tmpfs           <span class="hljs-number">1.6</span>G  <span class="hljs-number">1.6</span>M  <span class="hljs-number">1.6</span>G   <span class="hljs-number">1</span>% /run
tmpfs           <span class="hljs-number">7.8</span>G  <span class="hljs-number">176</span>M  <span class="hljs-number">7.7</span>G   <span class="hljs-number">3</span>% /dev/shm
tmpfs           <span class="hljs-number">5.0</span>M  <span class="hljs-number">4.0</span>K  <span class="hljs-number">5.0</span>M   <span class="hljs-number">1</span>% /run/lock
tmpfs           <span class="hljs-number">7.8</span>G     <span class="hljs-number">0</span>  <span class="hljs-number">7.8</span>G   <span class="hljs-number">0</span>% /sys/fs/cgroup
tmpfs           <span class="hljs-number">1.6</span>G   <span class="hljs-number">32</span>K  <span class="hljs-number">1.6</span>G   <span class="hljs-number">1</span>% /run/user/<span class="hljs-number">1000</span>
------------------------------------------------------

$ grep Shmem: /proc/meminfo
Shmem:            <span class="hljs-number">543796</span> kB

<span class="hljs-comment"># /dev/shm &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xC5D0; 100M &#xD06C;&#xAE30; &#xD30C;&#xC77C; &#xC0DD;&#xC131;</span>
$ dd bs=$(( <span class="hljs-number">2</span>**<span class="hljs-number">20</span> )) count=<span class="hljs-number">100</span> &lt; /dev/zero &gt; /dev/shm/hello
<span class="hljs-number">100</span>+<span class="hljs-number">0</span> records <span class="hljs-keyword">in</span>
<span class="hljs-number">100</span>+<span class="hljs-number">0</span> records out
<span class="hljs-number">104857600</span> bytes (<span class="hljs-number">105</span> MB, <span class="hljs-number">100</span> MiB) copied, <span class="hljs-number">0.043056</span> s, <span class="hljs-number">2.4</span> GB/s

$ grep Shmem: /proc/meminfo
Shmem:            <span class="hljs-number">646196</span> kB

$ rm <span class="hljs-operator">-f</span> /dev/shm/hello 

$ grep Shmem: /proc/meminfo
Shmem:            <span class="hljs-number">541804</span> kB
</code></pre>
<h1 id="2-">2 .</h1>
<p>&#xD604;&#xC7AC; &#xC0AC;&#xC6A9; &#xAC00;&#xB2A5;&#xD55C; cpu &#xAC1C;&#xC218;&#xB97C; &#xC54C;&#xB824;&#xBA74; &#xC5B4;&#xB5BB;&#xAC8C; &#xD560;&#xAE4C;&#xC694;?</p>
<pre><code class="lang-bash">$ nproc
<span class="hljs-number">8</span>

<span class="hljs-comment"># nproc &#xBA85;&#xB839;&#xC740; coreutils &#xD328;&#xD0A4;&#xC9C0;&#xC5D0; &#xD3EC;&#xD568;&#xB41C; &#xBA85;&#xB839;&#xC785;&#xB2C8;&#xB2E4;.</span>
$ dpkg -S /usr/bin/nproc
coreutils: /usr/bin/nproc

<span class="hljs-comment"># coreutils &#xD328;&#xD0A4;&#xC9C0;&#xC5D0; &#xD3EC;&#xD568;&#xB41C; &#xBA85;&#xB839;&#xB4E4;&#xC744; &#xBCF4;&#xB824;&#xBA74;</span>
$ dpkg -L coreutils
</code></pre>
<h1 id="3-">3 .</h1>
<p><code>df</code> &#xBA85;&#xB839;&#xC744; &#xC774;&#xC6A9;&#xD558;&#xBA74; &#xB9C8;&#xC6B4;&#xD2B8;&#xB41C; &#xD30C;&#xC77C; &#xC2DC;&#xC2A4;&#xD15C;&#xBCC4;&#xB85C; &#xB514;&#xC2A4;&#xD06C; &#xC0AC;&#xC6A9;&#xB7C9;&#xC744; &#xBCFC; &#xC218; &#xC788;&#xB294;&#xB370;&#xC694;.<br>&#xD2B9;&#xC815; &#xACBD;&#xB85C;&#xAC00; &#xC5B4;&#xB5A4; &#xD30C;&#xC77C; &#xC2DC;&#xC2A4;&#xD15C;&#xC5D0; &#xC18D;&#xD558;&#xB294;&#xC9C0; &#xB9C8;&#xC6B4;&#xD2B8; &#xC815;&#xBCF4;&#xB294; &#xC5B4;&#xB5BB;&#xAC8C; &#xC54C; &#xC218; &#xC788;&#xC744;&#xAE4C;&#xC694;?</p>
<pre><code class="lang-sh">$ <span class="hljs-built_in">cd</span> ~                  <span class="hljs-comment"># $HOME &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB85C; &#xC774;&#xB3D9;</span>

$ findmnt -T .          <span class="hljs-comment"># $HOME &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB294; &apos;/&apos; &#xC5D0; &#xB9C8;&#xC6B4;&#xD2B8;&#xB41C; /dev/sda5 &#xD30C;&#xC77C; &#xC2DC;&#xC2A4;&#xD15C;&#xC5D0; &#xC18D;&#xD55C;&#xB2E4;.</span>
TARGET SOURCE    FSTYPE OPTIONS
/      /dev/sda5 ext4   rw,relatime,errors=remount-ro

$ findmnt -T /dev/shm   <span class="hljs-comment"># /dev/shm &#xB514;&#xB809;&#xD1A0;&#xB9AC;&#xB294; /dev/shm &#xC5D0; &#xB9C8;&#xC6B4;&#xD2B8;&#xB41C; tmpfs &#xD30C;&#xC77C; &#xC2DC;&#xC2A4;&#xD15C;&#xC5D0; &#xC18D;&#xD55C;&#xB2E4;.</span>
TARGET   SOURCE FSTYPE OPTIONS
/dev/shm tmpfs  tmpfs  rw,nosuid,nodev

$ findmnt -o SOURCE -nT /home    <span class="hljs-comment"># -o &#xC635;&#xC158;&#xC744; &#xC774;&#xC6A9;&#xD558;&#xBA74; &#xD2B9;&#xC815; &#xD56D;&#xBAA9;&#xB9CC; &#xAD6C;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.</span>
/dev/sda5
</code></pre>

                    
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