Download the latest seafile server:
https://www.seafile.com/en/download/
Stop the server:
./seahub.sh stop ./seafile.sh stop
or via service:
/etc/init.d/seafile-server stop
Upgrade with upgrade scripts. Always start with the current version. If for instance your current version is 6.0.9 and want to upgrade to 6.2.5 do the following:
cd seafile-server-6.2.5/upgrade ./upgrade_6.0_6.1.sh ./upgrade_6.1_6.2.sh
Start the service
/etc/init.d/seafile-server start
References
Upgrade Seafile Server