Re: Moving LVM volume?
On Thu, 01 Jan 2015 11:30:02 +0100, Joe wrote:
> On Thu, 1 Jan 2015 01:54:39 +0000 (UTC)
> Frank Miles <fpm@u.washington.edu> wrote:
>
>> I recently added a new hard drive to my home system. I decided to use
>> it to create an all-new bootable 'jessie' system. I created a
>> partition table that I thought would be flexible:
>> /dev/sdb1 / (root) {7G} /dev/sdb2 /swap
>> {4GB} /dev/sdb3 /oldjunk {1G} /dev/sdb4 extended
>> {remainder} /dev/sdb5 LVM {one large volume}
>>
>> Most of the partitions- /usr, /home, /var, ... were in LVM2.
>>
>> What I've learned since then is that /usr seems to have special status,
>> and probably shouldn't be part of LVM as certain tasks early in the
>> boot process can't seem to access the interior of LVM.
>>
>> I've moved 'oldjunk' into the LVM, and want to expand this partition to
>> become the new /usr. I've shrunk the LVM, but the freed space is all
>> at the far end of the LVM. I have been unable to move it towards the
>> end of the disk space,
>> so I can expand /dev/sdb3. gparted, resize2fs, pvmove,... (running
>> from a CDROM-based rescue disk) have all failed.
>>
>> Is there some method that I've overlooked?
>>
> Is the system installed and running yet? If so, check the space used by
> the main mountpoints. Almost certainly, /usr is the largest of the
> system partitions. My workstation /usr is about 8GB, and I don't have
> any modern games. Excluding /home, the total is just over 10GB.
>
> Next, there's no problem having the entire system on LVM, including
> /boot. I still have a /boot partition, for legacy reasons, but the rest
> is in one LVM volume, indeed in a single partition apart from /home. On
> a workstation, there's no great advantage to using separate partitions
> for anything else.
>
> Next, unless you want to mess with the building of the boot ramdisk, the
> issue with /usr is that it must be mounted at the same time as the root
> partition gets mounted during boot, so it needs to be physically stored
> under /, and any separate /usr partition will still potentially have
> problems. At the moment, I'm not aware of any show-stoppers caused by
> having a separate /usr, but I've no doubt it will happen in time.
>
> To be honest, unless you already have a significant investment in the
> new system, I'd suggest starting again.
>
> --
> Joe
Thanks to everyone (Joe,Joel,Pascal,Tapani,Mark,...) for your interesting
replies. In response to your answers and questions:
I've been using the new-drive-system (jessie) for a bit over a week.
With the stock kernel it's mostly functional though 'systemctl status'
is whining about being 'degraded'. I probably wouldn't have discovered
that if my custom-kernel efforts* weren't failing in mysterious ways.
I was hoping that cleaning up the boot process would resolve the deeper
mysteries without having to think or work too hard.
/usr is currently taking ~11G. So there's not enough space to simply
merge the primary partitions and have / and /usr live on that. I do too
many different kinds of things to limit it - I expect it to grow, possibly
double in the next couple of years (and at that point this system will
probably get replaced anyway. the new disk is mainly to keep this old
system doddering along for a bit longer)
My proximal backup is the original disk, and I have tried to keep that
unaltered in developing the new system. I haven't (yet) backed-up to
my external backup drive - that's a bit of a pain to setup. I've had
drives fail on me, don't want to use that as /usr. I certainly wouldn't
trust a USB drive as /usr.
I guess I'm going to have to reinstall jessie from scratch. This will
take time as my network link is a slow DSL :( The alternatives don't
sound appealing. I have a lot of customization of my machines - hey,
if I just wanted to do what everyone else did I could run Windows.
So thanks again for your replies - I am at least satisfied that I've made
a reasonable effort to 'fix' the problems. I will have to think some
more about LVM - it seems like a great idea, but possibly not the best
option for my particular circumstances.
-Frank
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