openSUSE:Snapper FAQ

tagline: From openSUSE

Contents 1 Snapper FAQ 1.1 How do I enable snapshots for my /home file system? 1.2 Why does snapper never show changes in /var/log? 1.3 Does snapper support ext4? 1.4 Does snapper support LVM? 1.5 My system has high I/O load after running YaST or zypper. What can I do? 1.6 I'm not using openSUSE. Can I still use snapper? 1.7 I didn't install my system with YaST. How do I get started? 1.8 How do I add pre and post hooks (like YaST)? 1.9 Does snapper really revert everything?

Snapper FAQ

How do I enable snapshots for my /home file system?

You will have to create a snapper config for /home by calling:

 snapper -c home create-config /home

Why does snapper never show changes in /var/log?

For some directories we decided to disable snapshotting, e.g. /var/log since reverting logs makes searching for problems difficult. To exclude a path from snapshotting we create a subvolume for that path. You can see all subvolumes of / by calling "btrfs subvolume list /".

Does snapper support ext4?

Yes, but only experimental and you need a special kernel and e2fsprogs. For more information see the next4 project.

Does snapper support LVM?

Since version 0.0.12 snapper can handle LVM snapshots with thin-provisioning.

My system has high I/O load after running YaST or zypper. What can I do?

When running YaST or zypper snapper creates two snapshots and compares them. This comparison can cause high I/O load.

Since snapper version 0.0.10 you can disable the background comparisons in the config file /etc/snapper/configs/root by setting:

 BACKGROUND_COMPARISON="no"

Now you might also want to disable cleanup of empty pre-post snapshot pairs since otherwise the daily cleanup can cause high I/O.

 EMPTY_PRE_POST_CLEANUP="no"

I'm not using openSUSE. Can I still use snapper?

We provide snapper packages for various distributions in the openSUSE buildservice, see project and download. Of course you can also compile snapper from source, see development.

I didn't install my system with YaST. How do I get started?

After you have installed snapper packages you will have to create a config for your root filesystem by calling:

 snapper create-config /

Then continue with the tutorial.

How do I add pre and post hooks (like YaST)?

You will have to insert two calls to snapper in your program or script. In the first call use the option --print-number, remember the value and pass it on to the second call. Have a look at /sbin/yast2 to see how this can be done in bash or at /usr/lib/zypp/plugins/commit/snapper.py for python.

Since snapper version 0.0.9 you can also provide a command to snapper and snapper will create pre and post snapshots running the command in between, e.g.:

 snapper create --command "make install" --description "install mplayer"

Does snapper really revert everything?

Snapper will revert all files (text and binary) including permissions and ownership, also remove and recreate files and directories. File timestamps and ACL are not reverted. Some files are excluded, e.g. /etc/mtab.

It's recommended to always use the status command to see in advance what files snapper will process.