Restore/upgrade content db from backup

[0.7+] How to protect your Zotonic content and bring it back in case of disaster.

Contributed by: Scott Finnie

Why

Restore / upgrade the content for a site from a database dump.

Assumptions

1. zotonic >=0.7
2. Dump of content to restore. Could be created using backup cookbook (http://zotonic.com/documentation/856/backup-your-site). Alternatively, a dump can be created on the source machine with the following command (replace yoursitename with your site's db name):

zotonic:~$ sudo -u postgres pgdump zotonicyoursitename > zotonic-dump.sql

How

Overview

Dumps from postgres include both database structure (tables, sequences, constraints, etc.) as well as content. Therefore it's not possible to simply import the dump directly into an existing zotonic database populated with content. The target database must be empty before the dump can be imported. There are (at least) 2 ways to do this:

1. Drop contents of the target db and import the dump file;
2. Create a new database, import contents, rename old database to something temporary, rename new database to match site, and finally delete the old database.

Option 2 seems more involved but is safer and quicker:

• It's non-destructive. The old db remains intact until after the new one is activated. If anything goes wrong, you can fall back to the original
• It means less downtime. The site can stay live on the old db while the new db is being created. Downtime is restricted to the rename operations (which are quick and db size independent).

For small databases the downtime difference will be minimal. However the safety is appealing. Hence this cookbook uses the second approach.

Instructions

These assume the following naming conventions:

• your zotonic site is named yoursite.

• the postgres dump file to load is named zotonic-dump.sql.

• zotonic is installed in ~zotonic/zotonic

Replace as appropriate in all commands below.

1. Ensure db dump file is available on target machine (see pre-requisites)

2. Create a new database in postgres:

   zotonic:~$ sudo su -l postgres
   postgres:~$ ~zotonic/zotonic/bin/zotonic createdb yoursite_new
   CREATE DATABASE
   GRANT
   You are now connected to database "zotonic_yoursite_new".
   CREATE LANGUAGE
   postgres:~$
   

3. Import the dump file into the newly created db

   postgres:~$ psql -U zotonic -d zotonic_yoursite_new -f /path/to/zotonic-dump.sql
   […lots of SQL statements…]
   postgres:~$ 
   

   Note: the final sql commands shown will likely say 'no privileges could be revoked for "public"'. You can ignore this.

4. Stop zotonic (if running):

   postgres:~$ ~zotonic/zotonic/bin/zotonic stop 
   Stopping zotonic zotonic001@hostname
   Stop:'zotonic001@hostname'
   postgres:~$
   

5. Rename the databases:

   postgres:~$ psql
   postgres=# ALTER DATABASE zotonic_yoursite RENAME TO zotonic_yoursite_old; 
   ALTER DATABASE
   postgres=# ALTER DATABASE zotonic_yoursite_new RENAME TO zotonic_yoursite; 
   ALTER DATABASE
   postgres=# \q
   postgres:~$ exit
   zotonic:~$ 
   

6. Restart zotonic:

   zotonic:~$ ~/zotonic/bin/zotonic start
   

7. Browse to your site & test it's now serving updated content

8. [Optional]: Drop the old database:

   zotonic:~$ sudo -u postgres psql
   postgres=# DROP DATABASE zotonic_yoursite_old;
   DROP DATABASE
   postgres=# \q
   zotonic:~$  
   

Troubleshooting

There are no troubleshooting steps available for this guide.  Please provide any you have learned in the comments below or on the Zotonic Users Group.