Redmine

That is a database matter, not a redmine matter, but I suppose you could export the stuff out of mysql as plain sql and reimport it into postgresql. I'm sure google can help you with that. (redmine doesn't care what the db is, as long as it's configured in database.yml and contains the same data)

Unfortunately it's not a question of dump the mysql db and putting it into postgresql.
The underlying rails stuff does completely other things in mysql then in postgres.
For example boolean values are stored as integers in mysql for performance reasons where it
expects real booleans on postgresql. Next problem is, that mysql has some strange ideas how SQL should look like sometimes.
I've tried converting other rails apps from mysql to postgresql , it's a non trivial job and
I succeeded only in one of 5 cases.
Converting it on SQL level is basically almost impossible :-(
That's why I asked if there's some import/export feature.

This plugin might be useful for dumping the data and then importing it into the new database.

http://github.com/ludicast/yaml_db

You might also have some luck with the redmine_merge_redmine plugin from Eric, but I'd suggest asking him directly what he would suggest for this, got to the IRC channel and aks him (his nick is edavis10).

You might succeed with the following guide:

Installing, Migrating & Upgrading Redmine with LDAP on Ubuntu

For me it failed when I tried converting from SQLite 3 to MySQL, but migration to PostgreSQL was working fine.

when i click that link
page is not found

could you give alternative guide. I also want to migrate sqlite to Postgresql
thank you

got it
https://noobient.com/2013/12/01/installing-migrating-upgrading-redmine-with/

Better solution¶

http://www.redmine.org/boards/1/topics/58263