change-vdr-uid

#!/bin/bash

# Some defaults
set_force=0
old_uid=`cat /etc/passwd | awk -F":" '/VDR user/ {print $3}'`
old_gid=`cat /etc/passwd | awk -F":" '/VDR user/ {print $4}'`
new_uid=2000
new_gid=2000
find_opts='/etc/ /usr/ /var/ /srv/ -ignore_readdir_race'

print_usage()
{
    echo ""
    echo "Usage: change_vdr_uid.sh [options]"
    echo "          -f           force execution, no test mode"
    echo "          -g group id  new group id; default is $new_gid"
    echo "          -u user id   new user id; default is $new_gid"
    echo "          -h           just this"
    echo ""
}

process_parameters()
{
    while [ "$#" != 0 ]; do
        case $1 in
            -f) set_force=1
                shift
                ;;
            -g) new_gid=$2
                shift 2
                ;;
            -u) new_uid=$2
                shift 2
                ;;
            -h) print_usage
                exit
                ;;
            *)  echo "unknown option: $1"
                print_usage
                exit
                ;;
        esac
    done
}

change_passwd()
{
    cat /etc/passwd | awk 'BEGIN { FS=":" }
        { if ( $1 != "vdr" )
             { print }
          else
             { print $1 ":" $2 ":" '$new_uid' ":" '$new_gid' ":VDR user,,,:/var/lib/vdr:/bin/bash" } }' > /tmp/passwd
    if [ $? != 0 ]; then
        echo "Adjusting user id failed"
        exit 1
    fi
}

change_group()
{
    cat /etc/group | awk 'BEGIN { FS=":" }
        { if ( $1 != "vdr" )
             { print }
          else
             { print $1 ":" $2 ":" '$new_gid' ":" $4 } }' > /tmp/group
    if [ $? != 0 ]; then
        echo "Adjusting group id failed"
        exit 1
    fi
}

#
# Real processing starts here
#

process_parameters $@

# Remember files that have set setuid bit
suid_files=`find $find_opts -gid $old_gid -perm -4000`

change_passwd
change_group

if [ $set_force != 1 ]; then
    # Test mode; only report changes
    print_usage
    echo
    echo "Test mode: uid $old_uid -> $new_uid, gid $old_gid -> $new_gid"
    echo
    echo "Temporary changes in /tmp/passwd and /tmp/group"
    echo
    exit 0
fi

echo "Changing IDs: uid $old_uid -> $new_uid, gid $old_gid -> $new_gid"

mv /etc/passwd /etc/passwd.orig
mv /etc/group /etc/group.orig
mv /tmp/passwd /etc/passwd
mv /tmp/group /etc/group

# Adjust files
find $find_opts -gid $old_gid -exec chgrp vdr {} \;
find $find_opts -uid $old_uid -exec chown vdr {} \;
find $find_opts -type l -gid $old_gid -exec chgrp -h vdr {} \;
find $find_opts -type l -uid $old_uid -exec chown -h vdr {} \;

# Restoring setuid bits
for f in $suid_files; do
    echo "Adjusting setuid bit of $f"
    chmod 6750 $f
done