Migrate Postgresql 9.1 to 9.4 in 4 steps

By Jeff MacDonald [BSD], via Wikimedia Commons

$pg_lsclusters - Shows the currently running (online/down) postgres DB

$sudo pg_ctlcluster 9.1 main stop - Stops the running postgres 9.1

$sudo pg_upgradecluster 9.1 main - Upgrades(migrates) postgres to newer version(upgrade time depends on the amount of data).

Check whether the upgrade went fine and the newer version of postgres works fine by
$su postgres
postgres@xyz:/$ psql
psql (9.4.3)                       -  Now postgresql upgraded to new version
Type "help" for help.
postgres=#\l                     -   Check all your databases are available or not
postgres=#\c <your_database_name>  - Connects to your database
postgres=#select * from <your_table_name> - Check the content is same.

Optional:
$sudo pg_dropcluster 9.1 main  -  Do this only, If you really want to drop your old postgres cluster.

How to import mails to/Export mails from Icedove?

1. Download the following icedove add-on(ImportExporttools) from here.

2. Configure the add-on with your icedove client, steps are as follows.
Icedove --> Tools --> Add-ons

Now you will see a window like this ->


click on install button. Navigate to the downoalded ImportExportTools.xpi file and select it.

Now you will see a window like this ->

Once the "install" button enabled then click it. Your Icedove will automatically get restarted. Now you have the an option named "ImportExportTools"
in Icedove -> Tools ->

with sub options as show in the following image ->

So, Now if you want to export(backup) mails from icedove then select
Tools -> ImportExportTools -> Export options

If you want to import mails from some other backups(other mail client, but mbox format file) then select
Tools -> ImportExportTools -> Import options

Give a go through of all the available options in the Tools -> ImportExporttools and select the one which you want. Thats all now you are able to import/export backup your mails from icedove.

Note: Am using BOSS Linux 4.0, icedove version 3.0.7