cron-sync-backup-separate

Cron sync and backup (separate containers)

This demo shows a cron-based sync of IMAP to a local Maildir in /mail, and a cron-based backup of mail using restic, in separate containers.

Start the container(s):

docker-compose up

isync service is now running:

• /mbsyncrc config file is created
• /notify.sh is created
• A crontab is created that runs /sync and /notify.sh daily at 00:00
• crond is started

restic service is now running:

• /backup.sh is created
• /notify.sh is created
• A crontab is created that runs /backup.sh and /notify.sh daily at 00:05
• crond is started

1. Perform first-time sync

View /mbsyncrc config:

docker-compose exec isync cat /mbsyncrc

Run a first-time sync (this will fail, because [email protected] is not a real account. See next step):

docker-compose exec isync /sync

Since there's no such IMAP account as [email protected], let's create some files in /mail to simulate a successful sync:

docker-compose exec isync mkdir -p /mail/INBOX /mail/INBOX/cur /mail/INBOX/new /mail/INBOX/tmp
docker-compose exec isync touch /mail/INBOX/new/123 /mail/INBOX/new/456
docker-compose exec isync touch /mail/INBOX/.mbsyncstate /mail/INBOX/.uidvalidity

Finally, list the files:

docker-compose exec isync find /mail

2. Perform first-time backup

Perform a first-time backup of /mail using restic. This helps to ensure subsequent cron-based restic backups are speedy, since restic backups are incremental.

docker-compose exec restic /backup.sh

The backup should succeed:

Files:           4 new,     0 changed,     0 unmodified
Dirs:            5 new,     0 changed,     0 unmodified
Data Blobs:      0 new
Tree Blobs:      5 new
Added to the repository: 2.758 KiB (1.341 KiB stored)

processed 4 files, 0 B in 0:00
snapshot c9ed53b0 saved

3. Wait for cron sync

Now, wait out for 00:00 of tomorrow.

At 00:00, the incremental sync would run very quickly. A notification of the cron status would be sent to https://example.com using curl.

List synced files:

docker-compose exec isync find /mail

4. Wait for cron backup

Now, wait out for 00:05 of tomorrow.

At 00:05, the restic incremental backup would run very quickly. A notification of the cron status would be sent to https://example.com.

List synced files:

docker-compose exec isync find /mail

5. Restore a backup

If /mail is ever lost, restic restore can easily restore the data.

First, list the backup snapshots:

docker exec -it $( docker-compose ps -q restic ) restic snapshots

You should see a list of snapshots:

repository 5ba7868d opened (version 2, compression level auto)
ID        Time                 Host          Tags        Paths
--------------------------------------------------------------
c9ed53b0  2023-04-15 15:48:48  346a68a05c86  cron        /mail
81ec9c8f  2023-04-15 00:00:00  346a68a05c86  cron        /mail
--------------------------------------------------------------
2 snapshots

Restore the latest snapshot 81ec9c8f to the /restore volume:

docker exec -it $( docker-compose ps -q restic ) restic restore 81ec9c8f --target /restore

List restored files in /restore:

docker exec -it $( docker-compose ps -q restic ) find /restore

If all is well, clean out the /mail volume:

docker-compose exec restic sh -c 'find /mail -mindepth 1 -maxdepth 1 | xargs rm -rf'

Restore the latest snapshot 81ec9c8f to the /mail volume:

docker exec -it $( docker-compose ps -q restic ) restic restore 81ec9c8f --target /mail

List restored files in /mail:

docker exec -it $( docker-compose ps -q restic ) find /mail

The backup is fully restored.