19

I am using AWS as my cloud environment. I installed PostgreSQL on the same drive as my root instance volume. I have attached and mounted the second drive to my instance. Now I want to move all my PostgreSQL data to the different drive. I am still in development mode so I can delete the old data if it makes transfer easier at this point of time. What is the best way to do this?

Is PostgreSQL tablespace something which I should look at?

  • 1
    Tablespaces would be the way to go if you wanted to move part of your database(s) to a separate drive. – Erwin Brandstetter Nov 19 '12 at 23:42
  • This answer suggests that tablespaces should NOT go on an external hard drive: dba.stackexchange.com/a/62037/41823 Not sure I understand the risk if you're already putting the data on an external? – Statwonk Jun 29 '14 at 0:14
19

The following should do it:

  1. Shut down PostgreSQL
  2. Make sure PostgreSQL does not run any longer
  3. Check that PostgreSQL is really stopped
  4. Copy the old data directory to the new drive
    This is usually defined through a commandline parameter (-D) for your service or through the PGDATA environment variable.
  5. Update your PostgreSQL configuration (service, environment var) to point to the new data directory.
  6. If you copied the data, rename the old data directory to make sure PostgreSQL cannot find it any longer. That way you'll get an error message if you didn't get the configuration right.
  7. Start the service
  8. If everything is running fine, you can delete the old directory.
  • In 4th point, what do you mean by 'This is usually defined through a commandline parameter...'? – codecool Nov 19 '12 at 15:52
  • @codecool: there are several different ways how this could be defined. Usually it's part of the service definition. But it depends on your operating system, distribution and personal changes. – a_horse_with_no_name Nov 19 '12 at 15:54
  • This worked but I used the regedit instead of the command line for Windows. Whew. My disk was just about to run out of space but now I have it safely operating elsewhere with enough space. – trench Jul 13 '16 at 18:02
  • Here is nice step-by-step blog post with specific details, up-to-date for typical ubuntu and 9.5 DB version: digitalocean.com/community/tutorials/… – JaakL Jan 30 '17 at 21:04
4
  1. Stop postgresql service
  2. cp -a source_data_directory destination_data_directory
  3. chown -R postgres_user /destination_data_directory
  4. export PGDATA=destination_data_directory
  5. Changing data directory to destination_data_directory within postgresql.conf
  6. pg_ctl start
  • I glad you remembered the chown command for the new folder. – RolandoMySQLDBA May 6 '16 at 21:49
0

Here is a description of how to move an existing PostgreSQL database to a new location (folder, partition), on Arch Linux (this procedure should be similar for other Linux distributions).

pg_dumpall is a utility for writing out (dumping) all PostgreSQL databases of a cluster into one script file. ... It does this by calling pg_dump for each database in the cluster. ...

For example:

## To dump all databases:
$ pg_dumpall > /tmp/db.out               ## backup all postgres databases to file
$ pg_dumpall -Fc dbname > /tmp/outfile   ## backup a database

## To reload database(s) from that file:
$ psql -f /tmp/db.out postgres

TL/DR

You need to:

  • export (pg_dumpall) database
  • create new EMPTY directory
  • edit postgresql.conf file
  • restart postgres server service
  • load old data from dump file into new database

Summary of commands

I'm leaving my shell prompts (hostname ...) to clarify what shell I am in as I proceed.

[victoria@victoria ~]$ postgres --version     ## postgres (PostgreSQL) 11.2
[victoria@victoria claws]$ sudo -u postgres -i
[postgres@victoria ~]$ pg_dumpall > /tmp/db.out
[postgres@victoria ~]$ psql
[postgres]# SHOW data_directory;              ## /var/lib/postgres/data
[postgres]# exit
[victoria@victoria postgres]$ mkdir /mnt/Vancouver/programming/rdb/postgres/postgresdb
## IMPORTANT: dir must be empty:
[victoria@victoria postgres]$ l postgresdb/   ## total 0
[victoria@victoria postgres]$ sudo chown postgres:root /mnt/Vancouver/programming/rdb/postgres/postgresdb/
[victoria@victoria postgres]$ sudo systemctl status postgresql
  ...
  May 02 19:55:21 victoria systemd[1]: Started PostgreSQL database server.
[postgres@victoria ~]$ initdb --locale en_US.UTF-8 -E UTF8 -D '/mnt/Vancouver/programming/rdb/postgres/postgresdb/data'
[postgres@victoria ~]$ exit
[victoria@victoria postgres]$ sudo vim /var/lib/postgres/data/postgresql.conf
  ## added line:
  data_directory = '/mnt/Vancouver/programming/rdb/postgres/postgresdb/data'
[victoria@victoria postgres]$ sudo -u postgres -i
[postgres@victoria ~]$ psql
[postgres]# SHOW data_directory;
  ## /var/lib/postgres/data   ## << Old dir; need to restart postgresql service
[postgres]# \q
[victoria@victoria postgres]$ sudo systemctl restart postgresql
[victoria@victoria postgres]$ sudo -u postgres -i
[postgres@victoria ~]$ psql
[postgres]# SHOW data_directory;
  ## /mnt/Vancouver/programming/rdb/postgres/postgresdb/data
[postgres]# \q
[postgres@victoria ~]$ psql -f /tmp/db.out postgres
  SET
  SET
  SET
  CREATE ROLE
  ALTER ROLE
  [ ... SNIP! ... ]
[postgres@victoria ~]$ exit
## Done!  :-D

Example

See my accompanying blog post, How to Move an Existing PostgreSQL Database on Arch Linux, for commented code and output.---


References

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