Ext4 on FreeBSD

guillaje · #1 October 6th, 2011, 13:41

Hello,

I'm a Linux user, quite new to FreeBSD.
I recently installed FreeBSD 8.2-RELEASE amd64 as a backup server. These backups consist of the synchronisation between SAN snapshots of the FS I want to backup and ZFS filesytems.

In order to mount my Linux FS, I installed the port of e2fsprog, and it works great for ext2/3, but not for ext4 :

I can fsck it :

Code:

endor# fsck_ext2fs /dev/da1s2
e2fsck 1.41.14 (22-Dec-2010)
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
/dev/da1s2: 63569/657072 files (0.2% non-contiguous), 498732/2624256 blocks

But I can't mount it :

Code:

endor# mount -t ext2fs /dev/da1s2 /mnt
mount: /dev/da1s2 : Invalid argument

In dmesg:

Code:

WARNING: mount of da1s2 denied due to unsupported optional features

I tried to deactivate some ext4 features of this fs on a Debian box, but I can't disable all of them:

Code:

root@xen0adm1:~# tune2fs -O ^flex_bg /dev/iscsi/xen0adm1-2011-09-30-14p2
tune2fs 1.41.12 (17-May-2010)
Clearing the flex_bg flag would cause the the filesystem to be
inconsistent.
root@xen0adm1:~# tune2fs -O ^uninit_bg /dev/iscsi/xen0adm1-2011-09-30-14p2
tune2fs 1.41.12 (17-May-2010)
root@xen0adm1:~# tune2fs -O ^dir_index /dev/iscsi/xen0adm1-2011-09-30-14p2
tune2fs 1.41.12 (17-May-2010)
root@xen0adm1:~# tune2fs -O ^extents /dev/iscsi/xen0adm1-2011-09-30-14p2
tune2fs 1.41.12 (17-May-2010)
Clearing filesystem feature 'extent' not supported.

And after that, the error is the same when I try to mount it on FreeBSD.

So my question is, is it a way to mount an ext4 fs on FreeBSD? Even in ro, without journal.

Thank you,
jC

pkubaj · #2 October 6th, 2011, 14:14

Unfortunately, there's currently no way to mount ext4 slice. The original driver was created for ext2, still, it somehow works also with ext3, but not with ext4.

guillaje · #3 October 6th, 2011, 16:30

I read that it was not possible, but this page made me think I missed something...

"This project implements preallocation in ext2fs and update ext2fs to be able to read ext4 file systems and possibly add other functionality, such as write ext4 file systems."

fluca1978 · #4 October 6th, 2011, 17:05

Aren't ext3 and ext4 back compatible with ext2?

adamk · #5 October 6th, 2011, 18:40

ext3 mostly is, ext4 mostly is not

Adam

davidgurvich · #6 October 7th, 2011, 03:55

Ext3 is forward compatible with ext4. An ext4 system can be mounted as ext3 if extents aren't enabled. Is ext2fs feature complete for ext3?

**phoenix** · #7 October 8th, 2011, 05:46

You can mount an ext3 filesystem on FreeBSD by mounting it as ext2.

Last I checked, you could not mount an ext3 filesystem as ext3.

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