[Novalug] LVM Snapshots
James Ewing Cottrell 3rd
JECottrell3 at Comcast.NET
Sat Dec 18 22:34:50 EST 2010
Thanks for the answer, but you really didn't TELL me anything.
When you make a snapshot, the UUIDs are the same too. And it's a lot
more intuitive to change labels (e2label) than it is to change UUIDs. I
have done it before, but I'd have to look it up. Besides, I generally
make my labels the same name as the LV, and since I usually have only
one VG, they *are* unique.
Yes, snapshots are essentially copy-on-write co-dependent filesystems.
But my question still remains....Is It OK to run off a snapshot'ed
filesystem assuming I wanted to do that?
On 12/18/2010 3:05 PM, Peter Larsen wrote:
> Sorry for top posting. My andoids mail client sucks.
> Regarding snapshots and boot labels - don't. Use uuids and you're past that problem.
> The snapshots inherits all from the master including se-contexts. Labels are NOT unique so be very careful using them.
> Now I would be very suspecious of a sytem that tries to boot off a snapshot unless that was on the vm host for your guest os. But I see what you are trying to do. Rembember snapshots are two ways. If you create a snapshot and change the original the snapshot stays as the old was. So simply create a snapshot before you change anything; do your changes and test boot. If it fails revert to your snapshot and things are back to normal (takes a while to do since it rewrites all changed blocks).
> James Ewing Cottrell 3rd<JECottrell3 at Comcast.NET> wrote:
>> Is it OK to run off a snapshot? Let me clarify.
>> I installed some big software package and figured I'd take a snapshot to
>> save the starting configuration. It wanted me to do a reboot, and my
>> grub and fstab does mount points by label: root=LABEL=myrootlabel. Well,
>> I forgot to relabel the snapshot via e2label
>> and I believe that somehow the snapshot was the one that was booted
>> onto. I became suspicious later when things disappeared out of my /root
>> directory. Interestingly enough, I didn't find them in the other /root
>> directory either.
>> I had another case where I did something similar. I wanted to create
>> several variants of the Ubuntu distro: regular, KDS, and LXDE.
>> So I installed a text only version, added what I thought was a bunch of
>> cool stuff, and made a snapshot for each of the variants. That time I
>> actually did re2label the snapshots, and even changed the UUIDs, and did
>> the equivalent of a tasksel on each variant.
>> It worked for awhile, but at some point I couldn't get any of the
>> variants to boot or even the original text only version.
>> Any thoughts? SELinux was off on all systems.
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