11.
> systemd supports several kinds of dependencies between
> units. After/Before can be used to fix the ordering how units are
> activated. It is completely orthogonal to Requires and Wants, which
> express a positive requirement dependency, either mandatory, or
> optional. Then, there is Conflicts which expresses a negative
> requirement dependency. Finally, there are three further, less used
> dependency types.
12.
> systemd has a minimal transaction system. Meaning: if a unit is
> requested to start up or shut down we will add it and all its
> dependencies to a temporary transaction. Then, we will verify if the
> transaction is consistent (i.e. whether the ordering via After/Before
> of all units is cycle-free). If it is not, systemd will try to fix it
> up, and removes non-essential jobs from the transaction that might
> remove the loop. Also, systemd tries to suppress non-essential jobs in
> the transaction that would stop a running service. Non-essential jobs
> are those which the original request did not directly include but
> which where pulled in by Wants type of dependencies. Finally we check
> whether the jobs of the transaction contradict jobs that have already
> been queued, and optionally the transaction is aborted then. If all
> worked out and the transaction is consistent and minimized in its
> impact it is merged with all already outstanding jobs and added to the
> run queue. Effectively this means that before executing a requested
> operation, we will verify that it makes sense, fixing it if possible,
> and only failing if it really cannot work.
Ça va faire un sujet de recherche de plus pour les gens de MANCOOSI.
[^] # Re: Systemd
Posté par gasche . En réponse à la dépêche Fedora 14 en version alpha. Évalué à 1.
> systemd supports several kinds of dependencies between
> units. After/Before can be used to fix the ordering how units are
> activated. It is completely orthogonal to Requires and Wants, which
> express a positive requirement dependency, either mandatory, or
> optional. Then, there is Conflicts which expresses a negative
> requirement dependency. Finally, there are three further, less used
> dependency types.
12.
> systemd has a minimal transaction system. Meaning: if a unit is
> requested to start up or shut down we will add it and all its
> dependencies to a temporary transaction. Then, we will verify if the
> transaction is consistent (i.e. whether the ordering via After/Before
> of all units is cycle-free). If it is not, systemd will try to fix it
> up, and removes non-essential jobs from the transaction that might
> remove the loop. Also, systemd tries to suppress non-essential jobs in
> the transaction that would stop a running service. Non-essential jobs
> are those which the original request did not directly include but
> which where pulled in by Wants type of dependencies. Finally we check
> whether the jobs of the transaction contradict jobs that have already
> been queued, and optionally the transaction is aborted then. If all
> worked out and the transaction is consistent and minimized in its
> impact it is merged with all already outstanding jobs and added to the
> run queue. Effectively this means that before executing a requested
> operation, we will verify that it makes sense, fixing it if possible,
> and only failing if it really cannot work.
Ça va faire un sujet de recherche de plus pour les gens de MANCOOSI.