109 lines
4.6 KiB
Markdown
109 lines
4.6 KiB
Markdown
Migration guide
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====
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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.
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**Note:** this guide was written with Ubuntu Server 16.04 in mind; your mileage may vary for other setups.
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Basic steps
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----
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1. Set up a new Mastodon server using the [Production Guide](https://github.com/tootsuite/documentation/blob/master/Running-Mastodon/Production-guide.md) (however, don't run `db:setup`).
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2. Stop Mastodon on the old server (e.g. `systemctl stop 'mastodon-*.service'`).
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3. Dump and load the Postgres database using the instructions below.
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4. Copy the `system/` files using the instructions below.
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5. Run `RAILS_ENV=production bundle exec rails mastodon:feeds:build` to rebuild the home timelines for each user.
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6. Start Mastodon on the new server.
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7. Update your DNS settings to point to the new server.
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8. Update or copy your Nginx configuration, re-run LetsEncrypt as necessary.
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9. Enjoy your new server!
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Detailed steps
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----
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### What data needs to be migrated
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At a high level, you'll need to copy over the following:
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- The `~/live/public/system` directory, which contains user-uploaded images and videos
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- The Postgres database (using [pg\_dump](https://www.postgresql.org/docs/9.1/static/backup-dump.html))
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- The `~/live/.env.production` file, which contains server config and secrets
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Less crucially, you'll proably also want to copy the following for convenience:
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- The nginx config (under `/etc/nginx/sites-available/default`)
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- The systemd config files (`/etc/systemd/system/mastodon-*.service`), which may contain your server tweaks and customizations
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- The pgbouncer configuration under `/etc/pgbouncer` (if you're using it)
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### Dump and load Postgres
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Instead of running `db: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](https://www.postgresql.org/docs/9.1/static/backup-dump.html#BACKUP-DUMP-RESTORE)).
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Run this as the `mastodon` user on your new system:
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```bash
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createdb -T template0 mastodon_production
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```
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Next, create a Postgres dump on the old system (again, as the `mastodon` user):
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```bash
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pg_dump mastodon_production > dump.sql
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```
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Copy the `dump.sql` file over, using `scp` or `rsync`. Then on the new system, run:
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```bash
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psql mastodon_production < dump.sql
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```
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This will copy the Postgres database from the old system to the new one. You may see a warning about `no privileges could be revoked for "public"`, but [you can ignore it](https://confluence.atlassian.com/bamkb/errors-or-warnings-appear-when-importing-postgres-database-dump-829036698.html).
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Note that you will need to re-run this process from scratch (i.e. on a fresh database) if the old database changes after the dump.
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#### Dump and load as a different Postgres user
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If the Postgres username on the old server is different from the Postgres username on the new server, then you will have to use a slightly different technique. Run this to dump:
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```bash
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pg_dump -Fc mastodon_production -f backup.dump
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```
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Create the database like normal:
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```bash
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createdb -T template0 mastodon_production
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```
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Then load the dump using a special mode where the new user overwrites the old user (`--no-owner --role=<new_username>`), and only public schemas are used (`-n public`):
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```bash
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pg_restore -U <new_username> -n public --no-owner --role=<new_username> -d mastodon_production backup.dump
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```
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(Replace `<new_username>` with the new Postgres username above.)
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### Copy `system/` files
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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:
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```bash
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rsync -avz ~/live/public/system/ mastodon@example.com:~/live/public/system/
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```
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You'll want to re-run this if any of the files on the old server change.
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You can also copy over any other important files, such as `.env.production` and the nginx, systemd, and pgbouncer config files.
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### During migration
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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.
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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.
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### After migrating
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You can check [whatsmydns.net](http://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.
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