Re: [gentoo-amd64] Re: Disable fsck on boot, was: How to make watchdog start earlier during bootup?

[The Doctor]

Duncan wrote:

>> and, if you have experiences with it, do you know what could happen
>> without fsck on an unsafely unmounted luks partition?
>
> Luks I know nothing of.  Someday when I get the appropriate round tuit...

I just gave it a try with a 32 megabyte SD card on my laptop.  I set up
the LUKS volume like so:

root@windbringer ~:# cryptsetup -v -y -c aes-cbc-essiv:sha256 luksFormat
/dev/mmcblk0p1

...opened it:

root@windbringer ~:# cryptsetup luksOpen /dev/mmcblk0p1 test

...but I wasn't able to create a ReiserFS file system:

root@windbringer ~:# mkreiserfs -d /dev/mapper/test

[credits from mkreiserfs snipped]

Guessing about desired format.. Kernel 2.6.28 is running.
reiserfs_create_journal: cannot create a journal of 8193 blocks with 18
offset on 7456 blocks

Oops.  Too small a device, I guess.  So, I tried EXT3:

root@windbringer ~:# mkfs.ext3 -c -L test -v /dev/mapper/test
...
root@windbringer ~:# mount /dev/mapper/test /mnt/disk_image

To see what would happen, I copied a load of .jpg files over to the card
so there would be a test data set:

root@windbringer ~:# cp ~drwho/*.jpg /mnt/disk_image

Then I yanked the SD card out of the slot without unmounting it or
running the luksClose command of cryptsetup.  Much to my surprise,
nothing complained about it.  Upon reinserting it, however, the
following appeared in the kernel message buffer:

...
mmc0: card cb93 removed
Buffer I/O error on device dm-3, logical block 539
lost page write due to I/O error on dm-3
Aborting journal on device dm-3.
Buffer I/O error on device dm-3, logical block 369
lost page write due to I/O error on dm-3
journal commit I/O error
mmc0: new SD card at address cb93
mmcblk1: mmc0:cb93 S032B 29.6 MiB
 mmcblk1: p1

Nautilus prompted me to enter the LUKS passphrase to open the device;
checking the kernel message buffer showed that the journal recovery was
complete, and the volume could be properly read.  I checked the files
and none of them were corrupted.  Next test: delete a few files, don't
run sync(1), yank the card, and try again.  Kernel output:

...
mmc0: card cb93 removed
Buffer I/O error on device dm-4, logical block 419
lost page write due to I/O error on dm-4
Aborting journal on device dm-4.
Buffer I/O error on device dm-4, logical block 369
lost page write due to I/O error on dm-4
journal commit I/O error
ext3_abort called.
EXT3-fs error (device dm-4): ext3_put_super: Couldn't clean up the journal
Remounting filesystem read-only

After plugging the card back in:

...
mmc0: new SD card at address cb93
mmcblk1: mmc0:cb93 S032B 29.6 MiB
 mmcblk1: p1
kjournald starting.  Commit interval 5 seconds
EXT3 FS on dm-4, internal journal
EXT3-fs: recovery complete.
EXT3-fs: mounted filesystem with ordered data mode.

The deletions that took place before I pulled the card seemed to stay
deleted when the journal was replayed.  I did this four more times to
see what would happen, and I didn't encounter any file system corruption.

I haven't tried any other file systems yet, but if there is sufficient
interest I'll start walking through the contents of `cat
/proc/filesystems | grep -v ^nodev`

-- 

The Doctor [412/724/301/703]

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