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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 file, you can run:

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

A Sample backup script

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

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

Restoring the DB

If you need to restore from a pg_dumpall file, you need to first 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;"

# Restore from the .sql backup
cat db_dump.sql  |  docker exec -i FOLDERNAME_postgres_1 psql -U lemmy # restores the db

# 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'"

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');

delete from post_aggregates_fast;
insert into post_aggregates_fast select * from post_aggregates_view;

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

delete from comment_aggregates_fast;
insert into comment_aggregates_fast select * from comment_aggregates_view;

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

delete from user_fast;
insert into user_fast select * from user_view;

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

delete from community_aggregates_fast;
insert into community_aggregates_fast select * from community_aggregates_view;

More resources

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

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