This is the list of Frequently Asked Questions for restic.

restic check reports packs that aren’t referenced in any index, is my repository broken?

When restic check reports that there are pack files in the repository that are not referenced in any index, that’s (in contrast to what restic reports at the moment) not a source for concern. The output looks like this:

$ restic check
Create exclusive lock for repository
Load indexes
Check all packs
pack 819a9a52e4f51230afa89aefbf90df37fb70996337ae57e6f7a822959206a85e: not referenced in any index
pack de299e69fb075354a3775b6b045d152387201f1cdc229c31d1caa34c3b340141: not referenced in any index
Check snapshots, trees and blobs
Fatal: repository contains errors

The message means that there is more data stored in the repo than strictly necessary. With high probability this is duplicate data. In order to clean it up, the command restic prune can be used. The cause of this bug is not yet known.

How can I specify encryption passwords automatically?

When you run restic backup, you need to enter the passphrase on the console. This is not very convenient for automated backups, so you can also provide the password through the --password-file option, or one of the environment variables RESTIC_PASSWORD or RESTIC_PASSWORD_FILE. A discussion is in progress over implementing unattended backups happens in #533.


Be careful how you set the environment; using the env command, a system() call or using inline shell scripts (e.g. RESTIC_PASSWORD=password restic …) might expose the credentials in the process list directly and they will be readable to all users on a system. Using export in a shell script file should be safe, however, as the environment of a process is accessible only to that user. Please make sure that the permissions on the files where the password is eventually stored are safe (e.g. 0600 and owned by root).

How to prioritize restic’s IO and CPU time

If you’d like to change the IO priority of restic, run it in the following way

$ ionice -c2 -n0 ./restic -r /media/your/backup/ backup /home

This runs restic in the so-called best effort class (-c2), with the highest possible priority (-n0).

Take a look at the ionice manpage to learn about the other classes.

To change the CPU scheduling priority to a higher-than-standard value, use would run:

$ nice --10 ./restic -r /media/your/backup/ backup /home

Again, the nice manpage has more information.

You can also combine IO and CPU scheduling priority:

$ ionice -c2 nice -n19 ./restic -r /media/gour/backup/ backup /home

This example puts restic in the IO class 2 (best effort) and tells the CPU scheduling algorithm to give it the least favorable niceness (19).

The above example makes sure that the system the backup runs on is not slowed down, which is particularly useful for servers.

Creating new repo on a Synology NAS via sftp fails

Sometimes creating a new restic repository on a Synology NAS via sftp fails with an error similar to the following:

$ restic init -r sftp:user@nas:/volume1/restic-repo init
create backend at sftp:user@nas:/volume1/restic-repo/ failed:
    mkdirAll(/volume1/restic-repo/index): unable to create directories: [...]

Although you can log into the NAS via SSH and see that the directory structure is there.

The reason for this behavior is that apparently Synology NAS expose a different directory structure via sftp, so the path that needs to be specified is different than the directory structure on the device and maybe even as exposed via other protocols.

Try removing the /volume1 prefix in your paths. If this does not work, use sftp and ls to explore the SFTP file system hierarchy on your NAS.

The following may work:

$ restic init -r sftp:user@nas:/restic-repo init