Create README.md

Author: StuartIanNaylor

cvt2f2fs/README.md

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+# cvt2f2fs
+
+I copied this from https://www.raspberrypi.org/forums/viewtopic.php?p=1285848#p1285848 as have been trying to to a initramfs script
+where I do the same but in a pivot mount live without need of USB.
+Then noticed this script and thought well actually its just as valid.
+
+It occured to me that with block wear you and that mostly we are running with SD cards with much spare space that 10-20% overprovision is
+actually no big loss for many running specific applications.
+So hey why not use this script and f2fs the flash friendly file system.
+
+Script you have to hack slightly as it runs rpi-update and pulls in the kernel update for 4.19 which buster will reside on.
+Buster is only a couple of month away but the biggest problem is that if the kernel version and f2fs version beome out of sync you will get errors.
+You can log in via a normal sudo just do things in order and run
+sudo cvt2f2fs
+after reboot
+sudo cvt2f2fs --phase2
+after reboot
+sudo cvt2f2fs --phase3
+after reboot
+sudo cvt2f2fs --phase4
+
+So then you need to get f2fs-tools for buster as the script will run rpi-update.
+sudo vi /etc/apt/sources.list.d/10-buster.list
+
+deb http://mirrordirector.raspbian.org/raspbian/ buster main contrib non-free rpi
+
+sudo vi /etc/apt/preferences.d/10-buster
+
+Package: *
+Pin: release n=stretch
+Pin-Priority: 900
+
+Package: *
+Pin: release n=buster
+Pin-Priority: 750
+
+sudo apt-get update
+
+Now we can grab things from buster when we want
+sudo apt-get install -t buster f2fs-tools
+
+You need to do the above as you will notice in syslog `fsck.f2fs: invalid option -- 'y'` 
+Systemd seems to be trying to run with an invalid option
+The above fixes that and fsck.f2fs will run and report everything is fine.
+Thing is it will do that on every boot as the system thinks there is something wrong with the superblock.
+
+I thought OK dunno why this script is doing an rpi-update anyway and I know there where a lot of f2fs commits in 4.18 but lets hack the
+not to do the rpi-update bit.
+Strangely you get the same syslog messages invalid option -- 'y'` as the initramfs fsck.f2fs fails as it would seem the tools & kernel
+in stretch are not in version sync.
+I presume that we have had kernel updates but not f2fs-tools updates.
+
+Haven't done much more as f2fs was like I say an after thought that what is a huge over-provision of 10-20% is only approx 1-2gb
+of a 8/16gb sd card that most of us use.
+```
+-o overprovision-ratio-percentage
+              Specify the percentage over the volume size for overprovision area.  This  area  is
+              hidden to users, and utilized by F2FS cleaner. The default percentage is 5%.
+ ```
+ simple as mkfs.f2fs -o 20 /dev/mmcblk0p2
+ 
+ So included this here just for info as if you are using zram-conf other than just pure swaps then block and sd flash file systems might be of interest
+ I will get round to solving the above probs but just thought I would shout out and ask.
+
+Also there is one more thing that is confusing me 
+```
+-t nodiscard/discard
+              Specify  1  or  0  to  enable/disable  discard policy.  If the value is equal to 1,
+              discard policy is enabled, otherwise is disable.  The default value is 1.
+```
+
+f2fs has a optimised discard policy built in by default, but every example i see has an fstab or mount option with the discard directive set.
+I keep thinking is it fundemental to the file system surely we don't use the discard method that say ext4 would use.
+But it is confusing why with f2fs its specified at mkfs.f2fs -t 1 /dev/mmcblk0p2 and is the default.
+Dunno it doesn't make sense to need mount or fstab discard entries when its already set on creation?
+
+Anyone who uses f2fs please maybe explain as I will be adopting prob will wait for buster this summer but thought I would post and ask.
+