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Removing Restic Backup Snapshots

Tags Hostwinds,  Cloud servers,  dedicated hosting 

Restic backups store changes over time as a series of de-duplicated 'snapshots' of the server. Any given snapshot can restore any given file as it was at that time. If you make a lot of data changes, the backups in Object Storage can be quite large, and sometimes you want to tell restic to forget those changes. You can remove snapshots from the backups, and restic will automatically figure out what data needs to be preserved to keep a complete backup of the system but discard the changes in those snapshots. Hostwinds Cloud Backups defaults to 60 snapshots being stored, but that can be changed.

To remove previous snapshots, only two commands are required to run, "forget" and "prune" the details of how to do so are below -

As with any interaction with restic, you must first initialize the repo to perform actions within restic.

# restic snapshots
password is correct
ID Date Host Tags Directory
37f632eb 2018-02-22 11:32:43 all_databases.sql
b923eed6 2018-02-22 11:45:17 database_dump.sql
2 snapshots

Using the above example, there are 2 backups. To remove a snapshot, you need to know the ID of the snapshot, which is the first item in the available snapshots above.

In this example, we will be removing the second snapshot, which has the ID of b923eed6

# restic forget b923eed6
password is correct
storage ID 9babef79
removed snapshot b923eed6

Next, you will need to run a restic prune. This removes the data referenced in the snapshot removed from the restic repository, cleaning up unreferenced data.

An example of this can be seen below -

# restic prune
password is correct
storage ID 9babef79
counting files in repo
building new index for repo
[2:16] 100.00% 11981 / 11981 packs
repository contains 11981 packs (345057 blobs) with 56.676 GiB
processed 345057 blobs: 0 duplicate blobs, 0B duplicate
load all snapshots
find data that is still in use for 1 snapshots
[0:00] 100.00% 1 / 1 snapshots
found 2 of 345057 data blobs still in use, removing 345055 blobs
will remove 0 invalid files
will delete 11979 packs and rewrite 0 packs, this frees 56.664 GiB
counting files in repo
[0:00] 100.00% 2 / 2 packs
finding old index files
saved new indexes as [70561784]
remove 11 old index files
[1:12] 100.00% 11979 / 11979 packs deleted

It is advised to run a restic check after you prune to ensure you are aware if there are any internal data structures of the repository damaged.

The command being run and its output would be similar to that below -

# restic check
password is correct
create exclusive lock for repository
storage ID e7155fe8
load indexes
check all packs
check snapshots, trees and blobs
no errors were found

Now, when you view your backup snapshots, the entry you have removed will no longer be listed.

# restic snapshots
password is correct
ID Date Host Tags Directory
37f632eb 2018-02-22 11:32:43 all_databases.sql
1 snapshots

Written by Hostwinds Team  /  June 5, 2021

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