Re: [gentoo-user] Re: migrating to LVM

[Don Jerman]

On 10/19/07, Thufir <hawat.thufir@×××××.com> wrote:
> On Thu, 18 Oct 2007 10:26:49 +0200, Dirk Heinrichs wrote:
>
> > hda1: Windows
> > hda2: Linux (/boot)
> > hda3: Linux (/)
> > hda4: PV for LVM (PV = Physical Volume)
> > hdb1: PV for LVM
> >
> > The two PVs will be assigned to one Volume Group (VG), inside which you
> > want to create LVs (Logical Volumes) for /usr, /var, /home/<user>, swap,
> > ...
> >
> > Is this correct?
>
>
> Yes.
>
> Looking at <http://gentoo-wiki.com/
> HOWTO_Install_Gentoo_on_an_LVM2_root_partition>, and the section of the
> Gentoo Handbook it points to, critical system files would be on /
> partition, the root partition?
>
Usually, yes.  If /boot and /root are not members of the LVM volume
group it's much simpler to manage and recover from problems.

It's possible to put everything on LV's (apparently grub even supports
/boot on LV) but it means you have to have an initrd that can perform
the LVM initialization from the ramdisk and swap all the critical
partitions before starting the "real" init process.  If that
initialization goes wrong somehow it's not going to boot at all (no
"linux single" rescue mode) so you're stuck going back to a non-LV
boot method (CD, or a  "rescue partition" or something).  Once you get
the juggling act right the risk is fairly small, but it does add more
complexity to the boot process so there's more errors that can break
it.

So / and /boot will be smallish physical partitions - I use the
minimum size for /boot and around 10G for root, and LVM manages
anything that gets dynamically large or uncertain like /home/, /opt/,
and application directories like /var/lib/mythtv/ or /var/spool/mail/.
 Anything that starts to eat up a large part of my root partition is a
candidate for copying over to a LV later on.
-- 
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