The s6-rc-update program

s6-rc-update is an online service database switcher: it will replace your compiled service database with another one, and adjust the live state accordingly.

Live upgrading a service database is no small feat, and no fully automated system can get it right in all cases. s6-rc-update will do its best on its own, but it lets you give it instructions to handle difficult cases; and rather than implement doubtful heuristics, it will fail with an error message in situations it really cannot solve.

Interface

     s6-rc [ -v verbosity ] [ servicenames... ]

s6-rc expects to find a compiled service database in /etc/s6-rc/compiled and a live state in /s6/s6-rc. If it cannot find that data, it complains and exits.
- The compiled service database is built offline via the s6-rc-compile tool.
- The live state should be initialized at boot time via the s6-rc-init tool. It is then maintained by s6-rc itself.
The command line arguments servicenames... define a set of selected services the user wants to act on.
s6-rc computes the necessary transitions to bring the machine to the desired state - by default a state where all the services listed on the command line are up. If asked to, it performs those transitions.
s6-rc processes services as soon as they can be processed. It will wait until a service is up to start a dependent service, but it will start two independent services in parallel.
If every state transition completes successfully, s6-rc exits 0.
If a state transition fails, s6-rc will not perform the transitions that depend on it. It will wait until all the other independent transitions are done, then exit 1.

Options

s6-rc control

-v verbosity : be more or less verbose. Default is 1: warning and error messages will be printed to stderr. 0 silences warnings. 2 writes information messages whenever s6-rc performs a transition. 3 or more is debug info.
-n dryruntimeout : dry run. s6-rc will pretend to perform transitions, but will replace all its program invocations by a call to s6-rc-dryrun, which will do nothing but print the command line s6-rc would have executed, then sleep for dryruntimeout milliseconds before reporting success.
-t timeout : timeout. If s6-rc isn't done after timeout milliseconds, it will exit, leaving the live state as it is at exit time. It does not kill its children, so a child may successfully complete afterwards and the live state will not be updated; in that case, subsequent s6-rc invocations will notice and correctly update it.
-c compiled : look for the compiled service database in compiled. Default is /etc/s6-rc/compiled
-l live : look for the live state in live. Default is /s6/s6-rc

Up or down

-u : selected services are interpreted as to be brought up. This is the default.
-d : selected services are interpreted as to be brought down.

Service selection

-p : prune. The state will be brought to exactly servicenames..., plus their dependencies, and the other services will be brought down. With the -d option, the meaning is reversed: the state will be brought to the maximum possible set that does not include servicenames....
-a : all. Add the current set of active services to the selected set. This is useful to ensure consistency of the machine state, for instance, and also at shutdown time: s6-rc -da will stop all the currently active services.

Actions

-C : check. s6-rc will check the consistency of the database, and exit with an error message if it finds errors.
-L : list. s6-rc will resolve the given names, then print the list of corresponding atomic services to stdout, without taking their dependencies into account. It will print an empty line afterwards.
-A : list all. s6-rc will print the list of selected atomic services to stdout, after computing dependencies. Note that with the -d option, it computes reverse dependencies instead.
-S : state change. A state change will be performed for the selected services. This is the default if no other action option has been given.

Usage examples

 s6-rc myservicebundle

Brings up all the services represented by myservicebundle, dependencies first.

 s6-rc -Sad

Brings down all the services in an orderly manner. This is typically run at shutdown time.

 s6-rc -Au myservicebundle

Prints the names of all atomic services represented by myservicebundle, as well as everything they depend on.

 s6-rc -Ad myservicebundle

Prints the names of all atomic services represented by myservicebundle, as well as everything that depends on them.

 s6-rc -pun0 myservicebundle

Prints what s6-rc would do to bring the state to just myservicebundle and its dependencies.