e2fsck

[glennzo]

Has anyone ever had any reason to use e2fsck? Doesn't seem to be something discussed here too often. I have a drive that the system suggested running e2fsck on so I'm currently doing so since there are some issues with the box, not necessarily related to hard disks. Other than reading the man page I know little about it. Just wondering...

[stoat]

I'm not the voice of authority on it, but I used it a lot recently during some experiments with cloning partitions using simple terminal commands. It's what actually does the work when you run fsck on ext2 and ext3 partitions. I ran it before and after cloning a partition. And the utility resize2fs required me to run e2fsck first.

[glennzo]

Hi Stoat. I ran this today, as I stated. Never needed (or thought I needed) to use it in the past. Here's the result, which I believe is all good.

[root@phenom13 ~]# e2fsck /dev/sdc1
e2fsck 1.41.10 (10-Feb-2009)
FreeAgent contains a file system with errors, check forced.
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
FreeAgent: 117526/15269888 files (1.6% non-contiguous), 30945085/61049000 blocks
[root@phenom13 ~]# e2fsck /dev/sdc1
e2fsck 1.41.10 (10-Feb-2009)
FreeAgent: clean, 117526/15269888 files, 30945085/61049000 blocks
[root@phenom13 ~]#

[forkbomb]

I've had to run it a few times to fix file systems after cloning virtual machine disk images (for migrating from a small disk image to a bigger one for example).

In most distributions filesystem checks are done automatically after n mounts, n days, or if a file system appears to be dirty during the boot process (if you've ever suddenly lost power you probably saw this upon reboot). Hypothetically automatic checks shouldn't be done very often.

[stoat]

Originally Posted by glennzo

Here's the result, which I believe is all good.

To me, e2fsck appears to check the "Filesystem state" in the superblock (see sudo dumpe2fs -h /dev/sdxy). It is either "clean" or "not clean". If it's "clean", then I think e2fsck just reports that and stops. If it's "not clean", then it does it's thing. Your result looks like what I saw over and over with several different partitions recently. So I believe it's okay, too. Maybe something caused the filesystem not to be cleanly unmounted leaving that "not clean" filesystem state for e2fsck to find in the superblock.

I recently had e2fsck find a bunch of broken links. The source files for the links had vanished. They weren't really important files, but they had been buried in some system directory that I never visit. I recovered them from the DVD and re-established the links. But I still worry about that incident meaning something bad about that hard drive.

Maybe some expert will come along and explain it all to us better. Things like what that "non-contiguous" percentage means.

[Dies]

Originally Posted by stoat

Things like what that "non-contiguous" percentage means.

I'm no expert, but I believe that refers to how fragmented the drive is.

So in glennzo's case, not very.

[glennzo]

Originally Posted by stoat

To me, e2fsck appears to check the "Filesystem state" in the superblock (see sudo dumpe2fs -h /dev/sdxy). It is either "clean" or "not clean". If it's "clean", then I think e2fsck just reports that and stops. If it's "not clean", then it does it's thing. Your result looks like what I saw over and over with several different partitions recently. So I believe it's okay, too. Maybe something caused the filesystem not to be cleanly unmounted leaving that "not clean" filesystem state for e2fsck to find in the superblock.

I recently had e2fsck find a bunch of broken links. The source files for the links had vanished. They weren't really important files, but they had been buried in some system directory that I never visit. I recovered them from the DVD and re-established the links. But I still worry about that incident meaning something bad about that hard drive.

Maybe some expert will come along and explain it all to us better. Things like what that "non-contiguous" percentage means.

I'll buy the non-contigious stuff and the "not cleanly unmounted" claims too, especially since that machine (Quad Core Phenom) seems to like to lock up a lot lately, forcing a powercycle. The drive in question is an external USB Seagate FreeAgent, formatted EXT3 (obviously), and it is written to very often since it's the networked household backup device. This must be like defragmenting a Windows hard disk I'd imagine.