The HP-UX Parallel rc Framework

servi
ces or resources set up by script
a . Dependencies can be queried, added or changed using the
rcutil(1M) command. The options to query dependencies are divided into two parts:
1. The -d and -o options are used to query the dependencies between rc scripts.
2. The –a, -b and –p options are used to query the order of execution of rc scripts installed on the
system.
When a start script dependency is specified, the given script will execute only after the scripts it
depends on are executed. For example:
rcutil –s S370named:S340net,S220syslogd
Implies that S370named will execute only after S340net and S220syslogd.
The reverse is true for kill scripts - the given script will necessarily execute before the scripts it depends
on are executed. For example:
rcutil –k K478ppp:K992net.init,K660net,K660net-ipv6
Implies that K478ppp will execute before K992net.init, K660net and K660net-ipv6.
The –t option is used to make a script a throttle point. Making a script a throttle point guarantees
partial alphabetical ordering of that script with respect to other scripts. If a start script is made a
throttle point, then all scripts that are alphabetically greater than it are guaranteed to run after it.
Similarly, if a kill script is made a throttle point, then all scripts that are alphabetically less than it are
guaranteed to run before it. Throttle points are used when there are implicit or unknown
dependencies. In these circumstances, throttle points ensure compatible behavior.
Example 1:
Start script S023xyz initializes a disk device driver that many downstream scripts depend upon.
Making S023xyz a throttle point guarantees that it runs before all scripts that are alphabetically
greater than it.
Example 2:
In the sequential model any start script run after S128swc potentially depends on it. But the
developers of S128swc do not know which downstream script depends on it. S128swc can be made
a throttle point.
Note: Throttle points may reduce parallelism, so they must be used sparingly.
Dependencies can be queried, added or changed even when the Parallel rc Execution Infrastructure is
turned off. It is recommended that dependencies for an rc script be specified after thoroughly
understanding the rc script and the processes launched by the rc script.
Compatibility
The Parallel rc Framework was designed to be compatible with the traditional rc script sequencer.
When the Parallel rc Execution Infrastructure is turned off, the traditional rc script sequencer
automatically kicks in. This takes effect from the very next change in the run level.
When the Parallel rc Execution Infrastructure is turned on, scripts that have no dependency
information will have the below listed behavior:
1. For start scripts, all other start scripts within the run level whose names are alphabetically less than
the given script are guaranteed to run before the given script.