[systemd-devel] Difference between After and RequiredBy

[Peter Sztan]

Edward Z. Yang <ezyang <at> MIT.EDU> writes:

> are.  One particular point of contention is this: what is the
> difference between 'After' and 'RequiredBy'? Which is correct
> in this circumstance?
> 

After does not mean the unit is required, it only says that if
the unit mentioned is there, it should be ordered after it.
For example you have postgres.service which has
After=mysql.service, postgres will be ordered after mysql if 
and only if mysql.service is in the same "transaction" as
postgres is, if it's not, the order is undefined
(these service were not real in my example).