Re: [QUESTION] root ext4 strange couldn't mount/can mount report

[Theodore Tso <tytso@mit.edu>]

On Tue, Jan 27, 2009 at 02:37:14PM +0000, Nick Warne wrote:
> 
> I see.  I currently build ext3 in the kernel (as well as ext4), as
> I keep /boot partition ext3 for bootloader lilo.
> 
> So I can remove ext3 now, and lilo and kernel ext4 will happily read
> and use /boot partition as ext3 OK? 

The only thing which might not work is automatic type detection with
mount.  That is, if you specify:

	mount /dev/hda1 /boot

without specifying a filesystem type, /bin/mount will probably do an
automatic type detection, detect that the filesystem is an ext3
filesystem, and attempt to mount it as ext3, and not know to try it
with ext4.  Libraries such as blkid and fsid could be made smart
enough to do the right thing, but they don't at the moment.

But if you type "mout -t ext4 /dev/sda1 /boot", you can mount an ext3
filesystem using the ext4 filesystem driver, and with 2.6.29 and up,
you'll be able to mount ext2 filesystems using the ext4 filesystem
code.  (You'll also be able to create extent-based filesystems without
a journal, which is why Google contributed the support for this.)

       	     	       	      	       - Ted