Backup and Restore Guide

Docker and Ansible

When using docker or ansible, there should be a volumes folder, which contains both the database, and all the pictures. Copy this folder to the new instance to restore your data.

Incremental Database backup

To incrementally backup the DB to an .sql.gz file, you can run:

docker-compose exec postgres pg_dumpall -c -U lemmy | gzip > lemmy_dump_`date +%Y-%m-%d"_"%H_%M_%S`.sql.gz

For compression, you can use either gzip and gunzip, or xz and unxz.

A Sample backup script

#!/bin/sh
# DB Backup
ssh MY_USER@MY_IP "docker-compose exec postgres pg_dumpall -c -U lemmy" | gzip > ~/BACKUP_LOCATION/INSTANCE_NAME_dump_`date +%Y-%m-%d"_"%H_%M_%S`.sql.gz

# Volumes folder Backup
rsync -avP -zz --rsync-path="sudo rsync" MY_USER@MY_IP:/LEMMY_LOCATION/volumes ~/BACKUP_LOCATION/FOLDERNAME

Restoring the DB

To restore, run:

docker-compose up -d postgres

# Restore from the .sql.gz backup
gunzip < db_dump.sql  |  docker-compose exec -T postgres psql -U lemmy

If you've accidentally already started the lemmy service, you need to clear out your existing database:

# Drop the existing DB
docker exec -i FOLDERNAME_postgres_1 psql -U lemmy -c "DROP SCHEMA public CASCADE; CREATE SCHEMA public;"

# This also might be necessary when doing a db import with a different password.
docker exec -i FOLDERNAME_postgres_1 psql -U lemmy -c "alter user lemmy with password 'bleh'"

Then run the restore commands above.

Changing your domain name

If you haven't federated yet, you can change your domain name in the DB. Warning: do not do this after you've federated, or it will break federation.

Get into psql for your docker:

docker-compose exec postgres psql -U lemmy

-- Post
update post set ap_id = replace (ap_id, 'old_domain', 'new_domain');
update post set url = replace (url, 'old_domain', 'new_domain');
update post set body = replace (body, 'old_domain', 'new_domain');
update post set thumbnail_url = replace (thumbnail_url, 'old_domain', 'new_domain');

-- Comments
update comment set ap_id = replace (ap_id, 'old_domain', 'new_domain');
update comment set content = replace (content, 'old_domain', 'new_domain');

-- User
update user_ set actor_id = replace (actor_id, 'old_domain', 'new_domain');
update user_ set inbox_url = replace (inbox_url, 'old_domain', 'new_domain');
update user_ set shared_inbox_url = replace (shared_inbox_url, 'old_domain', 'new_domain');
update user_ set avatar = replace (avatar, 'old_domain', 'new_domain');

-- Community
update community set actor_id = replace (actor_id, 'old_domain', 'new_domain');
update community set followers_url = replace (followers_url, 'old_domain', 'new_domain');
update community set inbox_url = replace (inbox_url, 'old_domain', 'new_domain');
update community set shared_inbox_url = replace (shared_inbox_url, 'old_domain', 'new_domain');

More resources

https://stackoverflow.com/questions/24718706/backup-restore-a-dockerized-postgresql-database

Lemmy Documentation