What is the difference between "service restart" and "service reload"

I'm trying to understand the difference between service restart [someservice] and service reload [someservice]. I understand that restart restarts the service whereas reload reloads the configuration. But I don't understand the practical implications of this well enough to determine which I should use in a given context.

An example: most guides I've read for setting up PostgreSQL say that, once I've edited postgresql.conf and pg_hba.conf to allow remote connections, I should run:

sudo service postgresql restart

However, if I were to guess which to use based on the description above, I would choose reload.

In case it matters, I'm on Ubuntu 11.10, though I'm hoping for an as generally applicable explanation as possible.

• restart = stop + start
• reload = remain running + re-read configuration files.

What you said is correct, reload tells the service to reload its configuration files. That means it should be sufficient to reload the configuration; however there may be certain services that "don't follow the rule" or that won't reload config files. Due to this you're probably safer with restart. I personally do not use postgresql, so I don't know.