Migrating to a new machine

Sometimes, for various reasons, you may want to migrate your Mastodon instance from one server to another. Fortunately this is not too difficult of a process, although it may result in some downtime.

Basic steps

1. Set up a new Mastodon server using the Production Guide (however, don’t run mastodon:setup).
2. Stop Mastodon on the old server (e.g. systemctl stop 'mastodon-*.service').
3. Dump and load the Postgres database using the instructions below.
4. Copy the system/ files using the instructions below. (Note: if you’re using S3, you can skip this step.)
5. Copy the .env.production file.
6. Run RAILS_ENV=production bundle exec rails assets:precompile to compile Mastodon
7. Run RAILS_ENV=production ./bin/tootctl feeds build to rebuild the home timelines for each user.
8. Start Mastodon on the new server.
9. Update your DNS settings to point to the new server.
10. Update or copy your Nginx configuration, re-run LetsEncrypt as necessary.
11. Enjoy your new server!

Detailed steps

What data needs to be migrated

At a high level, you’ll need to copy over the following:

• The ~/live/public/system directory, which contains user-uploaded images and videos (if using S3, you don’t need this)
• The Postgres database (using pg_dump)
• The ~/live/.env.production file, which contains server config and secrets

Less crucially, you’ll probably also want to copy the following for convenience:

• The nginx config (under /etc/nginx/sites-available/default)
• The systemd config files (/etc/systemd/system/mastodon-*.service), which may contain your server tweaks and customizations
• The pgbouncer configuration under /etc/pgbouncer (if you’re using it)

Dump and load Postgres

Instead of running mastodon:setup, we’re going to create an empty Postgres database using the template0 database (which is useful when restoring a Postgres dump, as described in the pg_dump documentation).

Run this as the mastodon user on your old system:

pg_dump -Fc mastodon_production -f backup.dump

Copy the backup.dump file over, using rsync or scp. Then on the new system, create an empty database as the mastodon user:

createdb -T template0 mastodon_production

Then import it:

pg_restore -Fc -U mastodon -n public --no-owner --role=mastodon \
  -d mastodon_production backup.dump

(Note that if the username is not mastodon on the new server, you should change the -U AND --role values above. It’s okay if the username is different between the two servers.)

Copy files

This will probably take some time, and you’ll want to avoid re-copying unnecessarily, so using rsync is recommended. On your old machine, as the mastodon user, run:

rsync -avz ~/live/public/system/ mastodon@example.com:~/live/public/system/

You’ll want to re-run this if any of the files on the old server change.

You should also copy over the .env.production file, which contains secrets.

Optionally, you may copy over the nginx, systemd, and pgbouncer config files, or rewrite them from scratch.

During migration

You can edit the ~/live/public/500.html page on the old machine if you want to show a nice error message to let existing users know that a migration is in progress.

You’ll probably also want to set the DNS TTL to something small (30-60 minutes) about a day in advance, so that DNS can propagate quickly once you point it to the new IP address.

After migrating

You can check whatsmydns.net to see the progress of DNS propagation. To jumpstart the process, you can always edit your own /etc/hosts file to point to your new server so you can start playing around with it early.