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Jun 1, 2021

pg_back dumps databases from PostgreSQL

Description

pg_back is a dump tool for PostgreSQL. The goal is to dump all or some databases with globals at once in the format you want, because a simple call to pg_dumpall only dumps databases in the plain SQL format.

Behind the scene, pg_back uses pg_dumpall to dump roles and tablespaces definitions, pg_dump to dump all or each selected database to a separate file in the custom format. It also extract database level ACL and configuration that is not dumped by pg_dump older than 11. Finally, it dumps all configuration options of the PostgreSQL instance.

Features

  • Dump all or a list of databases
  • Dump all but a list of excluded databases
  • Include database templates
  • Choose the format of the dump for each database
  • Limit dumped schemas and tables
  • Dump databases concurrently
  • Compute a SHA checksum of each dump
  • Pre-backup and post-backup hooks
  • Purge based on age and number of dumps to keep
  • Dump from a hot standby by pausing replication replay
  • Encrypt and decrypt dumps and other files
  • Upload dumps to S3, GCS, Azure or a remote host with SFTP

Install

A compiled binary is available from the Github repository.

The binary only needs pg_dumpall and pg_dump.

Install from source

go get -u github.com/orgrim/pg_back

Use make to build and install from source (you need go 1.16 or above).

As an alternative, the following docker command downloads, compiles and puts pg_back in the current directory:

docker run --rm -v "$PWD":/go/bin golang:1.16 go get github.com/orgrim/pg_back

Minimum versions

The minimum version of pg_dump et pg_dumpall required to dump is 8.4. The oldest tested server version of PostgreSQL is 8.2.

Usage

Basic usage

Use the --help or -? to print the list of available options. To dump all databases, you only need to give the proper connection options to the PostgreSQL instance and the path to a writable directory to store the dump files.

If default and command line options are not enough, a configuration file may be provided with -c <configfilename> (see pg_back.conf). (Note: see below to convert configuration files from version 1.)

If the default output directory /var/backups/postgresql does not exist or has improper ownership for your user, use -b to give the path where to store the files. The path may contain the {dbname} keyword, that would be replaced by the name of the database being dumped, this permits to dump each database in its own directory.

To connect to PostgreSQL, use the -h, -p, -U and -d options. If you need less known connection options such as sslcert and sslkey, you can give a keyword=value libpq connection string like pg_dump and pg_dumpall accept with their -d option. When using connection strings, backslashes must be escaped (doubled), as well as literal single quotes (used as string delimiters).

The other command line options let you tweak what is dumped, purged, and how it is done. These options can be put in a configuration file. The command line options override configuration options.

Per-database configuration

Per-database configuration can only be done with a configuration file. The configuration file uses the ini format, global options are in a unspecified section at the top of the file, and database specific options are in a section named after the database. Per database options override global options of the configuration file.

In database sections of the configuration file, a list of schemas or tables can be excluded from or selected in the dump. When using these options, the rules of the -t, -T, -n and -N of pg_dump and pattern rules apply. See the documentation of pg_dump.

When no databases names are given on the command line, all databases except templates are dumped. To include templates, use --with-templates (-T), if templates are includes from the configuration file, --without-templates force exclude them.

Databases can be excluded with --exclude-dbs (-D), which is a comma separated list of database names. If a database is listed on the command line and part of exclusion list, exclusion wins.

Multiple databases can be dumped at the same time, by using a number of concurrent pg_dump jobs greater than 1 with --jobs (-j) option. It is different than --parallel-backup-jobs (-J) that controls the number of sessions used by pg_dump with the directory format.

Checksums

A checksum of all output files is computed in a separate file when --checksum-algo (-S) is different than none. The possible algorithms are: sha1, sha224, sha256, sha384 and sha512. The checksum file is in the format required by shaXsum (sha1sum, sha256sum, etc.) tools for checking with their -c option.

Purge

Older dumps can be removed based on their age with --purge-older-than (-P) in days, if no unit is given. Allowed units are the ones understood by the time.ParseDuration Go function: "s" (seconds), "m" (minutes), "h" (hours) and so on.

A number of dump files to keep when purging can also be specified with --purge-min-keep (-K) with the special value all to keep everything, thus avoiding file removal completly. When both --purge-older-than and --purge-min-keep are used, the minimum number of dumps to keep is enforced before old dumps are removed. This avoids removing all dumps when the time interval is too small.

Hooks

A command can be run before taking dumps with --pre-backup-hook, and after with --post-backup-hook. The commands are executed directly, not by a shell, respecting single and double quoted values. Even if some operation fails, the post backup hook is executed when present.

Encryption

All the files procuded by a run of pg_back can be encrypted using age (https://age-encryption.org/ an easy to use tool that does authenticated encryption of files). To keep things simple, encryption is done using a passphrase. To encrypt files, use the --encrypt option along with the --cipher-pass option or PGBK_CIPHER_PASS environment variable to specify the passphrase. When encrypt is set to true in the configuration file, the --no-encrypt option allows to disable encryption on the command line. By default, unencrypted source files are removed when they are successfully encrypted. Use the --encrypt-keep-src option to keep them or --no-encrypt-keep-src to force remove them and override the configuration file. If required, checksum of encrypted files are computed.

Encrypted files can be decrypted with the correct passphrase and the --decrypt option. When --decrypt is present on the command line, dumps are not performed, instead files are decrypted. Files can also be decrypted with the age tool, independently. Decryption of multiple files can be parallelized with the -j option. Arguments on the commandline (database names when dumping) are used as shell globs to choose which files to decrypt.

Please note that files are written on disk unencrypted in the backup directory, before encryption and deleted after the encryption operation is complete. This means that the host running pg_back must secure enough to ensure privacy of the backup directory and connections to PostgreSQL.

Upload to remote locations

All files produced by a run can be uploaded to a remote location by setting the --upload option to a value different than none. The possible values are s3, sftp, gcs, azure or none.

When set to s3, files are uploaded to AWS S3. The --s3-* family of options can be used to tweak the access to the bucket. The --s3-profile option only reads credentials and basic configuration, s3 specific options are not used.

When set to sftp, files are uploaded to a remote host using SFTP. The --sftp-* family of options can be used to setup the access to the host. The PGBK_SSH_PASS sets the password or decrypts the private key (identity file), it is used only when --sftp-password is not set (either in the configuration file or on the command line). When an identity file is provided, the password is used to decrypt it and the password authentication method is not tried with the server. The only SSH authentication methods used are password and publickey. If an SSH agent is available, it is always used.

When set to gcs, files are uploaded to Google Cloud Storage. The --gcs-* family of options can be used to setup access to the bucket. When --gcs-keyfile is empty, GOOGLE_APPLICATION_CREDENTIALS environment is used.

When set to azure, files are uploaded to Azure Blob Storage. The --azure-* family of options can be used to setup access to the container. The name of the container is mandatory. If the account name is left empty, an anonymous connection is used and the endpoint is used directly: this allows the use of a full URL to the container with a SAS token. When an account is provided, the URL is built by prepending the container name to the endpoint and scheme is always https. The default endpoint is blob.core.windows.net. The AZURE_STORAGE_ACCOUNT and AZURE_STORAGE_KEY are used when --azure-account and --azure-key are not set (on the command line or corresponding options in the configuration file).

The --purge-remote option can be set to yes to apply the same purge policy on the remote location as the local directory.

When files are encrypted and their unencrypted source is kept, only encrypted files are uploaded.

Restoring files

The following files are created:

  • pg_globals_{date}.sql: definition of roles and tablespaces, dumped with pg_dumpall -g. This file is restored with psql.
  • pg_settings_{date}.out: the list of server parameters found in the configuration files (9.5+) or in the pg_settings view. They shall be put back by hand.
  • ident_file_{date}.out: the full contents of the pg_ident.conf file, usually located in the data directory.
  • hba_file_{date}.out: the full contents of the pg_hba.conf file, usually located in the data directory.
  • {dbname}_{date}.createdb.sql: an SQL file containing the definition of the database and parameters set at the database or "role in database" level. It is mostly useful when using a version of pg_dump older than 11. It is restored with psql.
  • {dbname}_{date}.{d,sql,dump,tar}: the dump of the database, with a suffix depending of its format. If the format is plain, the dump is suffixed with sql and must be restored with psql. Otherwise, it must be restored with pg_restore.

When checksum are computed, for each file described above, a text file of the same name with a suffix naming the checksum algorithm is produced.

When files are encrypted, they are suffixed with age and must be decrypted first, see the [Encryption] section above. When checksums are computed and encryption is required, checksum files are encrypted and encrypted files are checksummed.

To sum up, when restoring:

  1. Create the roles and tablespaces by executing pg_globals_{date}.sql with psql.
  2. Create the database with {dbname}_{date}.createdb.sql if necessary.
  3. Restore the database(s) with pg_restore (use -C to create the database) or psql

Managing the configuration file

The previous v1 configuration files are not compatible with pg_back v2.

Give the path of the v1 configuration file to the --convert-legacy-config command line option, and pg_back will try its best to convert it to the v2 format. Redirect the output to the new configuration file:

pg_back --convert-legacy-config  pg_back1.conf > pg_back2.conf

The default configuration file can be printed with the --print-default-config command line option.

On some environments (especially Debian), you may have to add host = /var/run/postgresql to override the default /tmp host.

Testing

Use the Makefile or regular go test.

To run SQL tests requiring a PostgreSQL instance:

  1. run initdb in some directory
  2. start postgres
  3. load testdata/fixture.sql with psql
  4. use go test or make test with the PGBK_TEST_CONNINFO environment variable set to a libpq connection string pointing to the instance. For example :
PGBK_TEST_CONNINFO="host=/tmp port=14651" make test

Contributing

Please use the issues and pull requests features from Github.

License

PostgreSQL - See LICENSE file