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=== pm-utils ===
What is pm-utils?
* Provides simple shell command line tools to suspend and hibernate computer
that can be used to run vendor or distro supplied scripts on suspend and resume.
Why do we need it?
* As all the main distros are re-implimenting the same thing, over and over, to
do something that's really quite trivial.
Having the common locations for stuff means that software and hardware vendors
can just install one file to do the clever stuff.
* Distros can easily add/remove functionality by installing/removing one
file into the hooks directory, for example:
- enabling and disabling standby LED's on laptop hardware
- enabling suspend GUI's like suspend2
- re-enabling video
- starting and stopping services that can't cope with suspending
- re-syncing the time with ntp
- removing and modprobing modules when needed
- setting grub to be the default target for a hibernate-resume
- other wacky things that need doing on specific systems
How do "hooks" work?
* You put an executable file in /etc/pm/sleep.d. When suspend or
hibernate is called, several things happen:
1) a new virtual terminal is alloced and switched to
2) /etc/pm/config.d/* are evaluated in C sort order. These files can be
provided by individual packages outside of pm-utils. If a global config
variable is set, the value set to will overwrite the previous value.
If any other variable is set, it will be ignored.
3) each of /etc/pm/sleep.d/* are executed in C sort order. The first command
line argument is "suspend" or "hibernate". These files may source
configuration files from /etc/pm/config.d/ on their own in order to pick
up variables set there that aren't part of the global list. Note that
hooks should take care to preserve any global configuration variable
which _that_ hook will later need to use, as sourcing this config file
will clobber any such variables.
4) the system suspends or hibernates.
5) some event happens to wake the machine up
6) each of /etc/pm/sleep.d/* are executed in reverse C sort order. The first
command line argument is "resume" or "thaw".
7) the system switches back to the original virtual terminal from step 1.
That's it!
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