ZSH-based service monitoring

Generates service descriptions for runit according to single service description file (/etc/svtab).

Services are currently defined by run function, log function, check function (to see whether service should be up or down) and miscellaneous flags.

ZSV does not manage dependencies between services. Instead it uses arbitrary shell function to determine if specific service should be up or not. Service starting may change the state so that other services will start, but this requires calling the zsvgen executable to re-evaluate the dependencies.

Hook script zsv_ifupd is provided for netplugd and wpa_supplicant to trigger on network interface changes. It should be symlinked or copied to /etc/netplug.d/netplug and called using wpa_cli -a (bundled function for wpa_cli does this).

Format of the svtab file is as follows:

# comment
service1:flags:shell code
service2:flags:shell
  code spanning several lines
...

Both flags and shell code are optional and can be left out. Flags are sequence of ASCII letters. Lowercase letters turn specific feature off while uppercase turn it on. The default is defined in zsv_config and possibly overriden by /etc/zsvrc. Currently following flags are recognised:

• E: redirect stderr to stdout, so they are both logged
• M: manual operation - don't start or stop the service, just create it
• N: redirect the output to /dev/null

Shell code may set the variables runf, logf and checkf to override the defaults. It's also possible to define custom check() function there instead of setting checkf.

Name of the service has special meaning in a sense that it can change default values. Service name is first stripped of any text right of and including first . (dot) character and functions zsv_defaults_foo and zsv_run_foo (where foo is the stripped name) are looked for. The former is executed to fill in default values and the latter is set as default runf if found. The function setting defaults may use the rest of the service name to fill in values, so eg.: dhcpcd.eth0 sets the default run function to run dhcpcd and preconfigures it to use eth0 iface.

# System initialization, mount local filesystems, etc.
si::sysinit:/sbin/rc sysinit

# Further system initialization, brings up the boot runlevel.
rc::bootwait:/sbin/rc boot
zsv::bootwait:/usr/local/bzr/zsv/sbin/zsvgen /run/zsv.log

ru:2345:respawn:/usr/bin/runsvdir -P /run/service ................................................................................

syslog-ng
sshd
openntpd
vixie-cron
netplugd
wpa_supplicant.wlan0:M
wpa_cli.wlan0:M
dhcpcd.wlan0
dhcpcd.eth0
example_echo::checkf=zsv_check_route; run=( tcpserver 0.0.0.0 1234 cat )