This tutorial is full guide on how to take postgres backup and restore with examples. Besides, it is providing live exercises for hand on experience. This tutorial covers following topics:
1) PostgreSQL Logical backup
2) PostgreSQL Logical restore
3) PostgreSQL Physical Backups
4) PostgreSQL Physical Restores
5) Lab exercises covering Logical Backup & Restores
6) Lab exercise covering Physical Backup & Restores
This document is straight hit on goal of logical, physical backups and scheduling of jobs.
It is being considered below mention technologies install before implementation
1. CentOS 7
2. Postgresql 11
3. First Restore the provided database.
In Postgres, we have three fundamental approaches to make backup of Database objects
1. Logical Backup (SQL Dump)
2. Physical Backup (File System level Backup)
3. Point in time Recovery (Continues Archiving)
In Postgres SQL Dump backup is logical backup and it uses pg_dump utility for this purpose.The advantage of this backup is, it makes your life easy. Because it is easy to use and it is compatible with upgrading versions of OS and Postgres. But, file system level backups are dependent to Server Version and System architecture.
This method is to generate a file with the help of SQL commands and these files can feedback to the server. It will create the database in same state as it was at that time of dump creation. Pg_dump or pg_dumpall are the utilities provided by PostgreSQL fir this purpose.
Pg_dump Database_name > “Path of Foler”\Name of file.sql g_dump dumps a database as a text file or to other formats. Usage: pg_dump [OPTION]... [DBNAME] General options: -f, --file=FILENAME output file or directory name -F, --format=c|d|t|p output file format (custom, directory, tar, plain text (default)) -j, --jobs=NUM use this many parallel jobs to dump -v, --verbose verbose mode -V, --version output version information, then exit -Z, --compress=0-9 compression level for compressed formats --lock-wait-timeout=TIMEOUT fail after waiting TIMEOUT for a table lock --no-sync do not wait for changes to be written safely to disk -?, --help show this help, then exit Options controlling the output content: -a, --data-only dump only the data, not the schema -b, --blobs include large objects in dump -B, --no-blobs exclude large objects in dump -c, --clean clean (drop) database objects before recreating -C, --create include commands to create database in dump -E, --encoding=ENCODING dump the data in encoding ENCODING -n, --schema=SCHEMA dump the named schema(s) only -N, --exclude-schema=SCHEMA do NOT dump the named schema(s) -o, --oids include OIDs in dump -O, --no-owner skip restoration of object ownership in plain-text format -s, --schema-only dump only the schema, no data -S, --superuser=NAME superuser user name to use in plain-text format -t, --table=TABLE dump the named table(s) only -T, --exclude-table=TABLE do NOT dump the named table(s) -x, --no-privileges do not dump privileges (grant/revoke) --binary-upgrade for use by upgrade utilities only --column-inserts dump data as INSERT commands with column names --disable-dollar-quoting disable dollar quoting, use SQL standard quoting --disable-triggers disable triggers during data-only restore --enable-row-security enable row security (dump only content user has access to) --exclude-table-data=TABLE do NOT dump data for the named table(s) --if-exists use IF EXISTS when dropping objects --inserts dump data as INSERT commands, rather than COPY --load-via-partition-root load partitions via the root table --no-comments do not dump comments --no-publications do not dump publications --no-security-labels do not dump security label assignments --no-subscriptions do not dump subscriptions --no-synchronized-snapshots do not use synchronized snapshots in parallel jobs --no-tablespaces do not dump tablespace assignments --no-unlogged-table-data do not dump unlogged table data --quote-all-identifiers quote all identifiers, even if not key words --section=SECTION dump named section (pre-data, data, or post-data) --serializable-deferrable wait until the dump can run without anomalies --snapshot=SNAPSHOT use given snapshot for the dump --strict-names require table and/or schema include patterns to match at least one entity each --use-set-session-authorization use SET SESSION AUTHORIZATION commands instead of ALTER OWNER commands to set ownership Connection options: -d, --dbname=DBNAME database to dump -h, --host=HOSTNAME database server host or socket directory -p, --port=PORT database server port number -U, --username=NAME connect as specified database user -w, --no-password never prompt for password -W, --password force password prompt (should happen automatically) --role=ROLENAME do SET ROLE before dump If no database name is supplied, then the PGDATABASE environment variable value is used. Report bugs to <firstname.lastname@example.org>.
Step to take Postgres Backup and Restore
Open the terminal and follow these commands.
[umair@localhost ~]$ ## connect to postgres super user [umair@localhost ~]$ ################################## [umair@localhost ~]$ sudo su - postgres [sudo] password for umair: Last login: Tue Jun 23 01:16:02 PKT 2020 on pts/0 -bash-4.2$ psql psql (11.8) Type "help" for help.
Here we will check the list of all databases already exist in server.
postgres=# ## check how many databases already exist. postgres-# \l
Lists of database
List of databases Name | Owner | Encoding | Collate | Ctype | Acces s privileges -----------+----------+----------+-------------+-------------+-------- --------------- dirdb | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | mydb2 | myuser2 | UTF8 | en_US.UTF-8 | en_US.UTF-8 | newdb | testuser | UTF8 | en_US.UTF-8 | en_US.UTF-8 | postgres | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | template0 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/post gres + | | | | | postgre s=CTc/postgres template1 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | =c/post gres + | | | | | postgre s=CTc/postgres tutdb | postgres | UTF8 | en_US.utf8 | en_US.utf8 | (7 rows)
Four backup formats
- *.bak: compressed binary format
- *.sql: plaintext dump
- *.tar: tarball
- Directory Format
How to backup only one table?
-bash-4.2$ ### we will backup in plan text format. -bash-4.2$ pg_dump -d tutdb -p 5432 -U postgres -t customer -f /tmp/tempfile/custtab_20200623.txt -bash-4.2$ ### Its created
How to back up in insert file format?
-bash-4.2$ #### if you want to restore the plan text for format backup use psql utility -bash-4.2$ ### now we take backup in inserts format. -bash-4.2$ pg_dump -d tutdb -p 5432 -U postgres -t customer --inserts -f /tmp/tempfile/custtab_20200623.txt -bash-4.2$ ## its created please check the directory path.
How to take back up of Entire Database?
-bash-4.2$ ###Now we will take the backup of entire database. -bash-4.2$ pg_dump -d tutdb -p 5432 -U postgres --inserts -v -f /tmp/tempfile/entiretutdb_inserts_20200623.txt -bash-4.2$ ## you see here we add -v in pervious command. it verbose which shows about the all transection details and show you on screen
How to backup database in custom file format?
-bash-4.2$ ###Lets take the backup in custom format. Here we will add -F c and this format is not human readable. This is the only format use for pg_restore for restore of database. -bash-4.2$ pg_dump -d tutdb -p 5432 -U postgres -F c -v -f /tmp/tempfile/entiretutdb_custom_20200623.txt
How to take backup database in directory format?
Before entering this command, please make sure particular directory has been created with full permission for user.
-bash-4.2$ ## lets take the backup in diecctory format -bash-4.2$ ## first create the directory and give permissions for postgres or group users. -bash-4.2$ ## i have created the directory /tmp/tempfile/bkdir -bash-4.2$ ##here we will use directory name instead of file name -bash-4.2$ pg_dump -d tutdb -p 5432 -U postgres -F d -v -f /tmp/tempfile/bkdir
You can use –j at the end of above command to make threads of backup process and catalyze the process. Here I am creating three threads.
-bash-4.2$ pg_dump -d tutdb -p 5432 -U postgres -F d -v -f /tmp/tempfile/bkdir -j 3
How to restore postgres database?
Essential Step before Restore
Since the text files generated by pg_dump contain a set of SQL commands, they can fed to the psql utility. The database itself will not create by psql, so you must create it yourself from template0 first. So, the general command form to restore a dump is:
createdb -T template0 database_name psql database_name < database.sql
Before start to restore an SQL dump. The creation of the objects with the original ownership and/or permissions. it is crucial to make sure that all users who have granted permissions on objects., or who own objects in the uploaded database, already exist. Otherwise, the restoration process will fail.
How to restore the database from plan text file format?
Here we will restore only one table. Please use psql utility for restore of plan text file format backup.
-bash-4.2$ ## first we will restore the plan text format. As we discussed we will use psql. -bash-4.2$ psql -d tutdb -p 5432 -U postgres -f /tmp/tempfile/custtab_20200623.txt
How to create new database and restore existing database in custom format?
-bash-4.2$ ### Now we will restore full data . first we drop tutdb and then create again/ -bash-4.2$ psql psql (11.8) Type "help" for help. postgres=# drop database tutdb; DROP DATABASE postgres=# create database tutdb; CREATE DATABASE postgres=# \l postgres=# \q -bash-4.2$ ### now we restore full database. -bash-4.2$ ## here i will use custom format. -bash-4.2$ pg_restore -d tutdb -U postgres -p 5432 /tmp/tempfile/entiretutdb_custom_20200623.txt -bash-4.2$ ## database populated lets see -bash-4.2$ psql psql (11.8) Type "help" for help. postgres=# \c tutdb You are now connected to database "tutdb" as user "postgres". tutdb=# tutdb=# \dt tutdb=# select * from actor; tutdb=# \q -bash-4.2$ ####it perfectly done -bash-4.2$ #### lets create an other user and try to restore database from directory dump formate. -bash-4.2$ ### lets do it.
How to restore database from directory format?
postgres=# drop database dirdb; DROP DATABASE postgres=# create database dirdb; CREATE DATABASE postgres=# \q -bash-4.2$ pg_restore -d dirdb -U postgres -p 5432 /tmp/tempfile/bkdir -bash-4.2$ ### its restores lets see -bash-4.2$ psql psql (11.8) Type "help" for help. postgres=# \c dirdb You are now connected to database "dirdb" as user "postgres". dirdb=# \dt ### its perfectly done.
Objects Definitions Backup
Use the following command to backup all objects in all databases.
roles, databases, tablespaces, tables, schemas, indexes, functions, triggers, constraints, privileges, views, and ownerships:
pg_dumpall –U postgres --schema-only > “MyPATH”\definitions.sql Use the following command to backup the role definition only: pg_dumpall –U postgres --roles-only > “MyPATH”\roles.sql Use the following command to backup the tablespaces definition: pg_dumpall –U postgres --tablespaces-only > “MyPATH”\tablespaces.sql
All physical backups are dependent on source and target architecture.
It also depends on version, compiler flags and paths. Source and target environment must be equal.
File System Level Backup
[umair@localhost Documents]$ ### create directory for archive logs [umair@localhost Documents]$ sudo -H -u postgres mkdir /var/lib/postgresql/pg_log_archive [sudo] [umair@localhost Documents]$ ## enable archive logging [umair@localhost Documents]$ sudo nano /var/lib/pgsql/11/data/postgresql.conf [umair@localhost Documents]$ systemctl restart postgresql-11 [umair@localhost Documents]$ ## create a database with insert data [umair@localhost Documents]$ sudo su - postgres Last login: Thu Jun 25 00:01:24 PKT 2020 on pts/1 -bash-4.2$ psql -c "create database testdb" CREATE DATABASE password for umair: psql testdb -c " > create table posts ( > id integer, > title character varying(100), > content text, > published_at timestamp without time zone, > type character varying(100) > ); > > insert into posts (id, title, content, published_at, type) values > (100, 'Intro to SQL', 'Epic SQL Content', '2018-01-01', 'SQL'), > (101, 'Intro to PostgreSQL', 'PostgreSQL is awesome!', now(), 'PostgreSQL'); > " INSERT 0 2 -bash-4.2$ ## achive the logs -bash-4.2$ psql -c "select pg_switch_wal();" pg_switch_wal --------------- 0/C01E1E0 (1 row) -bash-4.2$ ##backup database -bash-4.2$ pg_basebackup -Ft -D /var/lib/postgresql/db_file_backup -bash-4.2$ ##Stop database -bash-4.2$ systemctl stop postgresql-11 -bash-4.2$ rm var/lib/pgsql/11/data/* -r rm: cannot remove ‘var/lib/pgsql/11/data/*’: No such file or directory -bash-4.2$ rm /var/lib/pgsql/11/data/* -r -bash-4.2$ ls /var/lib/pgsql/11/data/ -bash-4.2$ ls /var/lib/pgsql/11 backups data initdb.log -bash-4.2$ ##restore files -bash-4.2$ tar xvf /var/lib/postgresql/db_file_backup/base.tar -C /var/lib/pgsql/11/data/ backup_label tablespace_map pg_wal/ ./pg_wal/archive_status/ global/ global/1262 global/1262_fsm global/2964 global/1213 global/1213_fsm global/1136 global/1136_fsm global/1260 global/1260_fsm global/1261 global/1214 global/2396 global/6000 global/3592 global/6100 global/2846 global/2847 global/2966 global/2967 global/4060 … … … bash-4.2$ tar xvf /var/lib/postgresql/db_file_backup/pg_wal.tar -C /var/lib/pgsql/11/data/ 00000001000000000000000E -bash-4.2$ ##add recovery config -bash-4.2$ nano /var/lib/pgsql/11/data/postgresql.conf -bash-4.2$ -bash-4.2$ -bash-4.2$ -bash-4.2$ ###restore_command = 'cp /var/lib/postgresql/pg_log_archive/%f %p' -bash-4.2$ ###restore command added -bash-4.2$ ##start db -bash-4.2$ systemctl start postg[umair@localhost Documents]$ sudo su - postgres Last login: Thu Jun 25 00:01:24 PKT 2020 on pts/1 -bash-4.2$ psql -bash-4.2$ # verify restore was successful Point in time recovery PITR [umair@localhost Documents]$ # backup database and gzip [umair@localhost Documents]$ sudo su - postgres Last login: Thu Jun 25 00:01:24 PKT 2020 on pts/1 -bash-4.2$ pg_basebackup -Ft -X none -D - | gzip > /var/lib/postgresql/db_file_backup.tar.gz # wait -bash-4.2$ psql testdb -c "insert into posts (id, title, content, type) values > (102, 'Intro to SQL Where Clause', 'Easy as pie!', 'SQL'), > (103, 'Intro to SQL Order Clause', 'What comes first?', 'SQL');" -bash-4.2$ # archive the logs -bash-4.2$ psql -c "select pg_switch_wal();" -bash-4.2$ # stop DB and destroy data -bash-4.2$ systemctl stop postgresql-10 -bash-4.2$ rm /var/lib/pgsql/11/data/* -r -bash-4.2$ ls /var/lib/postgresql/10/main/ -bash-4.2$ # restore -bash-4.2$ tar xvfz /var/lib/postgresql/db_file_backup.tar.gz -C /var/lib/pgsql/11/data/ -bash-4.2$ # add recovery.conf -bash-4.2$ nano /var/lib/postgresql/10/main/recovery.conf restore_command = 'cp /var/lib/postgresql/pg_log_archive/%f %p' recovery_target_time = '2020-06-25 15:20:00 EST' -bash-4.2$ # start DB -bash-4.2$ systemctl start postgresql-11 # verify restore was successful -bash-4.2$ psql test -c "select * from posts; -bash-4.2$ # complete and enable database restore -bash-4.2$ psql -c "select pg_wal_replay_resume();"
You have follow this guide of postgres backup and restore. Now, you should do following expercies.
Lab Exercises for postgres backup and restore
Lab Exercise -1
The tutdb database is all setup and as a DBA you need to plan a proper backup strategy and implement it.
- As the root user, create a folder /bkupdir and assign ownership to the tutdb user using the chown utility.
- Take a full dataase dump of the tutdb database with the pg_dump utility. The dump should be in plain text format.
- Nathe dump file as tutdb_full_Data.sql and store it in the /bkupdir directory.
Lab Exercise – 2
- Take the dump backup of tutdb schema and name the file as as tutdb_schema.sql
- Take a data only dump of the tutdb database, disable all triggers for faster restore, use the INSERT command instead of COPY, and name the fie as tutdb_data.sql
- Take a full dump of actors table and name the file as tutdb_actors.sql.
Lab Exercise – 3
- Take a full database dump of tutdb in compressed format using the pd_dump utility, name the file as tutdb_full.dmp
- Take a full database cluster dump using pg_dumpall. Remember pg_dumpall supports only plain text format; name the file tutdb.sql
Lab Exercise – 4
In this exercise you will demonstrate your ability to restore a database.
- Drop database tutdb
- Create database tutdb with owner superuser
- Restore the full dump from tutdb_full.sql and verify all the objects and their ownership.
- Drop database tutdb.
- Create database tutdb with superuser owner
- Restore the full dump from the compressed file tutdb_full_fc.dmp and verify all the objects and their ownership.
Lab Exercise -5
- Create a directory /opt/arch and give ownership to the superuser.
- Configure your cluster to run in archive mode and set the archive log location to be /opt/arch.
- Take a full online base backup of your cluster in the /pgbackup directory using the pg_basebackup utility.
Lab Exercise – 6
A database cluster can encounter different types of failures. Recover your database from a variety of simulated failures:
- Recover from loss of the postgresql.conf file
- Recover fom loss of an actors table data file.
- Recover from mistakenly drop table actors.
Lab Exercise – 7
- Create new database name demodb and insert few records.
- Check database archive log is enabling in postgresql.conf file. If you find not enable take necessary action.
- Make file base backup using pg_basebackup and restore
Lab Exercise – 8
- Create a new database pitrdb and insert records.
- Take backup using pg_basebackup() in .tar.gz format.
- Set recovery target time.
- Restore these backup and keep database running.
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