borgmatic

How to backup your databases

Database dump hooks

If you want to backup a database, it's best practice with most database systems to backup an exported database dump, rather than backing up your database's internal file storage. That's because the internal storage can change while you're reading from it. In contrast, a database dump creates a consistent snapshot that is more suited for backups.

Fortunately, borgmatic includes built-in support for creating database dumps prior to running backups. For example, here is everything you need to dump and backup a couple of local PostgreSQL databases, a MySQL/MariaDB database, and a MongoDB database:

hooks:
postgresql_databases:
- name: users
- name: orders
mysql_databases:
- name: posts
mongodb_databases:
- name: messages

As part of each backup, borgmatic streams a database dump for each configured database directly to Borg, so it's included in the backup without consuming additional disk space. (The exceptions are the PostgreSQL/MongoDB "directory" dump formats, which can't stream and therefore do consume temporary disk space. Additionally, prior to borgmatic 1.5.3, all database dumps consumed temporary disk space.)

To support this, borgmatic creates temporary named pipes in ~/.borgmatic by default. To customize this path, set the borgmatic_source_directory option in the location section of borgmatic's configuration.

Also note that using a database hook implicitly enables both the read_special and one_file_system configuration settings (even if they're disabled in your configuration) to support this dump and restore streaming. See Limitations below for more on this.

Here's a more involved example that connects to remote databases:

hooks:
postgresql_databases:
- name: users
hostname: database1.example.org
- name: orders
hostname: database2.example.org
port: 5433
username: postgres
password: trustsome1
format: tar
options: "--role=someone"
mysql_databases:
- name: posts
hostname: database3.example.org
port: 3307
username: root
password: trustsome1
options: "--skip-comments"
mongodb_databases:
- name: messages
hostname: database4.example.org
port: 27018
username: dbuser
password: trustsome1
authentication_database: mongousers
options: "--ssl"

If you want to dump all databases on a host, use all for the database name:

hooks:
postgresql_databases:
- name: all
mysql_databases:
- name: all
mongodb_databases:
- name: all

Note that you may need to use a username of the postgres superuser for this to work with PostgreSQL.

If you would like to backup databases only and not source directories, you can specify an empty source_directories value (as it is a mandatory field prior to borgmatic 1.7.1):

location:
source_directories: []
hooks:
mysql_databases:
- name: all

New in version 1.7.1 You can omit source_directories entirely.

External passwords

If you don't want to keep your database passwords in your borgmatic configuration file, you can instead pass them in via environment variables or command-line configuration overrides.

Configuration backups

An important note about this database configuration: You'll need the configuration to be present in order for borgmatic to restore a database. So to prepare for this situation, it's a good idea to include borgmatic's own configuration files as part of your regular backups. That way, you can always bring back any missing configuration files in order to restore a database.

Supported databases

As of now, borgmatic supports PostgreSQL, MySQL/MariaDB, and MongoDB databases directly. But see below about general-purpose preparation and cleanup hooks as a work-around with other database systems. Also, please file a ticket for additional database systems that you'd like supported.

Database restoration

To restore a database dump from an archive, use the borgmatic restore action. But the first step is to figure out which archive to restore from. A good way to do that is to use the rlist action:

borgmatic rlist

(No borgmatic rlist action? Try list instead or upgrade borgmatic!)

That should yield output looking something like:

host-2019-01-01T04:05:06.070809      Tue, 2019-01-01 04:05:06 [...]
host-2019-01-02T04:06:07.080910 Wed, 2019-01-02 04:06:07 [...]

Assuming that you want to restore all database dumps from the archive with the most up-to-date files and therefore the latest timestamp, run a command like:

borgmatic restore --archive host-2019-01-02T04:06:07.080910

(No borgmatic restore action? Upgrade borgmatic!)

With newer versions of borgmatic, you can simplify this to:

borgmatic restore --archive latest

The --archive value is the name of the archive to restore from. This restores all databases dumps that borgmatic originally backed up to that archive.

This is a destructive action! borgmatic restore replaces live databases by restoring dumps from the selected archive. So be very careful when and where you run it.

Repository selection

If you have a single repository in your borgmatic configuration file(s), no problem: the restore action figures out which repository to use.

But if you have multiple repositories configured, then you'll need to specify the repository path containing the archive to restore. Here's an example:

borgmatic restore --repository repo.borg --archive host-2019-...

Restore particular databases

If you've backed up multiple databases into an archive, and you'd only like to restore one of them, use the --database flag to select one or more databases. For instance:

borgmatic restore --archive host-2019-... --database users

Limitations

There are a few important limitations with borgmatic's current database restoration feature that you should know about:

  1. You must restore as the same Unix user that created the archive containing the database dump. That's because the user's home directory path is encoded into the path of the database dump within the archive.
  2. As mentioned above, borgmatic can only restore a database that's defined in borgmatic's own configuration file. So include your configuration file in backups to avoid getting caught without a way to restore a database.
  3. borgmatic does not currently support backing up or restoring multiple databases that share the exact same name on different hosts.
  4. Because database hooks implicitly enable the read_special configuration setting to support dump and restore streaming, you'll need to ensure that any special files are excluded from backups (named pipes, block devices, character devices, and sockets) to prevent hanging. Try a command like find /your/source/path -type b -or -type c -or -type p -or -type s to find such files. Common directories to exclude are /dev and /run, but that may not be exhaustive.

Manual restoration

If you prefer to restore a database without the help of borgmatic, first extract an archive containing a database dump.

borgmatic extracts the dump file into the username/.borgmatic/ directory within the extraction destination path, where username is the user that created the backup. For example, if you created the backup with the root user and you're extracting to /tmp, then the dump will be in /tmp/root/.borgmatic.

After extraction, you can manually restore the dump file using native database commands like pg_restore, mysql, mongorestore or similar.

Preparation and cleanup hooks

If this database integration is too limited for needs, borgmatic also supports general-purpose preparation and cleanup hooks. These hooks allows you to trigger arbitrary commands or scripts before and after backups. So if necessary, you can use these hooks to create database dumps with any database system.

Troubleshooting

MySQL table lock errors

If you encounter table lock errors during a database dump with MySQL/MariaDB, you may need to use a transaction. You can add any additional flags to the options: in your database configuration. Here's an example:

hooks:
mysql_databases:
- name: posts
options: "--single-transaction --quick"

borgmatic hangs during backup

See Limitations above about read_special. You may need to exclude certain paths with named pipes, block devices, character devices, or sockets on which borgmatic is hanging.

Alternatively, if excluding special files is too onerous, you can create two separate borgmatic configuration filesβ€”one for your source files and a separate one for backing up databases. That way, the database read_special option will not be active when backing up special files.

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