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Re: Converting / to ext3.



On Wednesday, November 01 2000, Sam Varshavchik said:

> On Wed, 1 Nov 2000, Jeremy Katz wrote:
> 
> > Also, you'll want to change the type of / to be ext3 instead of ext2 in
> > /etc/fstab (obviously) and then everything "just works".  Or at least,
> > it's worked for me :)
> 
> It doesn't appear necessary to add the journal= flag to /etc/fstab in
> addition to rootflags=. It looks to me like the either the /etc/fstab
> options not reread when root gets remounted in rw mode, or if an ext3
> journal exists, you don't have to specify it when remounting root.
>
> I just succesfully converted / to ext3.  I made sure by killing the
> system, and rebooting, and I did not put the journal option in /etc/fstab.  
> Very interesting.

Correct.  The inode of the journal is stored as an options flag in the
superblock similar to how other ext2 attributes such as the sparse flag
are stored.  This is really nice in that you can switch your filesystems
back to ext2 in /etc/fstab (eg to upgrade your system through the
installer) and then later when you switch them back, don't have to go
through the process of telling the kernel where the journal is located.
 
[snip]
> image=/boot/vmlinuz-2.2.17-6
>         label=linux
>         read-only
>         append="rootflags=journal=83408"
>         root=/dev/hda8
> 
> Just like for ext2 you need to boot with / mounted read-only.  When I
> killed the laptop, at boot there was a message that / will be temporarily
> mounted rw while ext3 rebuilds it, then it goes back to readonly until
> initscripts remounts it.

Note that you only need the append line for the first boot mounting as
ext3, as after that, the journal inode is stored in the superblock as
described above.  

Jeremy

-- 
Jeremy Katz
katzj linuxpower org	| jlkatz eos ncsu edu
http://linuxpower.org	| Developer, NCSU Realm Kit for Red Hat Linux
GPG fingerprint: 367E 8B6B 5E57 2BDB 972A 4D73 C83C B4E8 89FE 392D

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