commit bae53ea1e1d5542779d60d609456a129f1d4ef09
parent 2fbb0b5149234cf9b651e79c9417c6d56f4ff4c9
Author: Cem Keylan <cem@ckyln.com>
Date: Sat, 4 Jul 2020 00:42:54 +0300
docs: add documentation
Diffstat:
1 file changed, 53 insertions(+), 0 deletions(-)
diff --git a/docs/service-scripts.txt b/docs/service-scripts.txt
@@ -0,0 +1,53 @@
+Creating Service Scripts
+--------------------------------------------------------------------------------
+
+Service scripts can be anything from C binaries to shell scripts. All they need
+is to be executable. However, given the simplicity of the services, most of them
+are better written in POSIX sh. A simple service could be as following:
+
+ +--------------------------------------------------------------------------+
+ | /etc/sysmgr/acpid |
+ +--------------------------------------------------------------------------+
+ | |
+ | #!/bin/sh |
+ | exec acpid -f |
+ | |
+ +--------------------------------------------------------------------------+
+
+If you are familiar with acpid, you may have noticed the '-f' flag, which makes
+sure that the program is daemonized, and the program stays in the foreground.
+This is important, because sysmgr expects that the program doesn't fork itself
+to the background. That's how we are tracking its process id. Usually service
+programs such as SSHD, NTPD, DHCPCD, etc. have a flag for staying in the
+foreground, and the service script must make use of such flags.
+
+Another thing you may have noticed is the 'exec' part of the service. In shell,
+'exec' makes the shell exit and run the given program with its own process id.
+This is also necessary to track the correct process.
+
+
+Service dependencies
+--------------------------------------------------------------------------------
+
+Some services may depend on other services in order to start working. An example
+for this is NetworkManager which depends on dbus in order to launch. sysmgr
+comes with a utility named sysmgr-needs which can be used to manage service
+dependencies. Here are example service scripts for NetworkManager and dbus.
+
+ +--------------------------------------------------------------------------+
+ | /etc/sysmgr/dbus |
+ +--------------------------------------------------------------------------+
+ | |
+ | #!/bin/sh |
+ | mkdir -p /run/dbus |
+ | exec dbus-daemon --system --nofork --nopidfile |
+ | |
+ +--------------------------------------------------------------------------+
+ | /etc/sysmgr/NetworkManager |
+ +--------------------------------------------------------------------------+
+ | |
+ | #!/bin/sh |
+ | sysmgr-needs dbus |
+ | exec NetworkManager -n |
+ | |
+ +--------------------------------------------------------------------------+
