Feature changed by: Stefan Hundhammer (shundhammer)
Feature #320834, revision 18
Title: [BETA 1 / 2] Create a /var/cache subvolume
Requested by: Thorsten Kukuk (kukuk)
Developer: YaST Maintainers mailing-list (yast2-maintainers)
Partner organization: openSUSE.org
Description:
On the openSUSE Factory list, somebody found a valid bug in our current
setup for snapshots: /var/cache is part of the snapshot.
This means: all RPMs used for an update are part of the snapshot as
they will be only deleted after creating the snapshot. This is a big
problem if you regular update online, it will eat up your diskspace
very fast. The same is true for all other cached data, there is no real
sense in having them included into a snapshot, since they change very
fast, they will only eat up disk space.
We need to add /var/cache to the list of directories, for which we
create a subvolume with btrfs.
And (that's why I created a FATE and no bug) we need to add something
to the release notes, so that customers are aware of this and can
create the subvolume at their own for existing installations.
Documentation Impact:
snapper.xml
Business case (Partner benefit):
openSUSE.org: Save disk space by excluding irrelvant/outdated cached
data from snapshots.
Discussion:
#1: Hannes Kühnemund (hkuehnemund) (2016-05-04 13:33:56)
Just read the conversation on research and passed on to PrjMgr.
#2: Jiri Srain (jsrain) (2016-05-05 13:28:59)
Updated yast2-storage is on its way to SP2:GA
(https://build.suse.de/request/show/114103).
Keeping open for now, since the release notes entry to document how to
create such subvolume in an installed system (without having any side
effects) is missing.
#3: Thorsten Kukuk (kukuk) (2016-05-10 13:42:43)
I added some first, rough text for the release-notes.
#4: Stefan Brüns (stefanbruens) (2016-05-18 03:07:18)
on openSUSE, / is not created as subvolume @ (at least it was not with
13.2).
Documentation how to mv /var/cache in this case would be nice
+ #5: Stefan Hundhammer (shundhammer) (2016-05-18 17:18:48) (reply to
+ #4)
+ Thanks for the hint, added that case to the release notes section.
Release Notes: Move /var/cache into an own subvolume for snapshots and
rollback
Challenge:
/var/cache contains a lot of very volatile data, like the zypper cache
with RPM packages in a lot of different versions for each update. Due
to this volatility, the size a snapshot needs increases very fast for
data that are mostly redundant.
Solution:
To solve this, /var/cache should be moved into a separate subvolume. If
you install with SLES12 SP2 or newer, this is done automatically during
installation. For existing root file systems, do these steps manually:
- Identify the parent subvolume of all the other subvolumes. For SLE 12
and recent Tumbleweed installations, this is a subvolume named "@". For
openSUSE 13.2 and older Tumbleweed installations, this it the unnamed
toplevel subvolume with ID 5. Check if you have a '@' subvolume:
btrfs subvolume list / | grep '@'
If the output of this command is empty, you don't have a subvolume
named '@'. In that case, use the subvolume with ID 5.
- Mount that subvolume to a temporary mount point (using /mnt in this
description).