How do I defrag ext4?

[waterfoul]

fsck reports 18905 non-contiguous files (20.9%) and 40 non-contiguous directories (0.0%) on an ext4 file system so I would really like to defragment it. Is there any way?

[coffee412]

Make really, really, really sure that the file system is not mounted. usually boot from install disk. Then run this command:

fsck.ext4 -P /dev/sdXX

X= Your partition info


Of course for further info just type this:

man fsck.ext4

[waterfoul]

Make really, really, really sure that the file system is not mounted. usually boot from install disk. Then run this command:

fsck.ext4 -P /dev/sdXX

X= Your partition info


Of course for further info just type this:

man fsck.ext4

Didn't do anything

[SlowJet]

He wants to defrag the files and dir's.

I think the issue is very mute and he would need to know what file are involved.
#e2freefrag /dev/mapper/VolGroup-LogVol will show he extent sizes with numbers
#frrefrag /home/useryou/Documents/* shows fragmetaion of files; drill down as needed
man pages available,

#e2defrag or online defrag or background defrag is not installed.
There may be one that works, it may need kernel patches and compiled, and it may contain bugs.
But officially, there is no ext4 defrag yet.

SJ

[diamond_ramsey]

waterfoul, disregard my above post, review the e2freefrag instructions by SlowJet.

man 8 e2freefrag

I misunderstood about wanting to do a fsck, deleting my post now.

[mathan]

i use this command in root prompt , but its say unable to umount the disk error

i wanna defrag to root filesystem drive

[stevea]

To manually defrag or fsck root you want to boot a live CD or similar and manipulate the umounted filesystem.

[sidebrnz]

Of course you can't unmount the root filesystem when it's in use. Boot from a LiveCD and try it that way.

You're actually better off backing up your drive, reformatting and restoring. Linux normally spreads files out all over the drive, both to avoid fragmenting and to lower the average seek time. Defragging packs them all at one end, the way Windows stores them. Not only do they get fragmented faster, the average seek time goes up. Backing up, nuking and restoring keeps them spread out, the way they're supposed to be. HTH, HAND.

[kc9aop]

If you want to defrag/check the root file system do this:

1. touch /forcefsck
2. reboot

The file forcefsck will cause a file system check at boot time.

Jim

[DBelton]

actually, with ext4, you can defrag while online (mounted)

just use the e4defrag program (included in the e2fsprogs package.)

just run:

e4defrag /dev/sdXx (where sdXx is the partition of the filesystem you wish to defrag, like sda4)

The forcefsck at boot will check the filesystem, but won't defrag it.

Edit:

Forgot to mention that you have to run e4defrag with the -test parameter for now, since it isn't a fully tested version. it requires the -test parameter, I guess just to make certain that you realize it's still a test version.

[bkorb]

Something to consider: the disk someone wants to defrag may be virtualized. My goal is to minimize the rolled up size of an entire virtual machine. I could zero out all the unused file space, but then the unrolled machine will take up all the space of the virtual disks with real zeros. So, yes, I really do want to move all the data to one end of the virtual disk. Then I can shut the virtual machine down and run a virtual machine host tool to delete the unused file system pages. viola' my machine image is smaller. I do wish my e2fsprogs actually did have the e4defrag thingy......

[sidebrnz]

Yes, that will work, right up to the moment when you need to write something to that partition, such as a new kernel, and you find out that there's no room because you've very cleverly removed all of the free space. Some things really are better left alone.

[bkorb]

Compacting the files has no effect on that. These are unroll-often, ugrade-rarely VM's. So trans-global distribution time is actually an issue. OS upgrades causing fragmentation, not so much. I also realized you thought I would resize the partition. Nope. Just compact the data so it both uses less host disk space and compresses better.

[george_toolan]

Can't you just copy the files to a new virtual drive?

[bkorb]

Can't you just copy the files to a new virtual drive?

Yes, indeed, that works. If there were an e4defrag-er out there, it would be easier. I've found references to such a beast, but no working links to it. Creating a new bootable disk with a swap and an fs partition is a nuisance, so, I thought I'd ask. Thank you.