[WIP] feat: lvm: Add lvm-based backup functionality #78
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This commit implements the needs of roles-ansible#75[^1]: it allows for the creation of atomic backups when the backup target is a file/dir whose fs rests on LVM. This ensures the snapshot will be atomic. By using a mount namespace, the LVM snapshot can be done in the same directory -- so existing LVM-based applications of ansible_role_restic can be migrated to this implementation without any discontinuity in what appears to be backed up. This combination of LVM's snapshotting layer and mount namespaces comes with some caveats: - you cannot backup / due to namespace issues - subdirs with a separate fs won't be correctly detected - not all filesystems are happy about LVM snapshots -- btrfs, e.g. - LVM snapshots come with a performance penalty when active - fstrim and LVM snapshots don't like each other whatsoever [^1]: roles-ansible#75 -- Changes in v2: - Use `findmnt -v` to find snapshot when cleaning up - Check for _snap before `lvremove -y` Signed-off-by: Martin Kennedy <[email protected]>
Grr! this is really frustrating. We need more "tracking" for the snapshot we created.
This commit causes an LVM backup target of / to be treated as /rootfs instead. Note that this will conflict with a path called /rootfs if we *do* try to back that up. Also, while we're at it, drop the -m option from mount. Not all systems have this option.
Before this commit, since restic backup exits with status 3 if it cannot read one or more files, the LVM snapshot wasn't being cleaned up. Now, specially handle the 3 exit status; also, unequivocally perform the LVM cleanup when finished.
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tanks |
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This series implements the needs of #75 through the use of LVM snapshots + mount namespaces.
It's a WIP at this point, as both the implementation and documentation around it need cleanup.