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Diffstat (limited to 'doc/mdevd.html')
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1 files changed, 21 insertions, 23 deletions
diff --git a/doc/mdevd.html b/doc/mdevd.html index 14d2867..0ea61bb 100644 --- a/doc/mdevd.html +++ b/doc/mdevd.html @@ -19,8 +19,8 @@ <h1> The <tt>mdevd</tt> program </h1> <p> -<tt>mdevd</tt> is a uevent manager. It reads a series of -uevents on its stdin; for every uevent it reads, it performs +<tt>mdevd</tt> is a uevent manager. It connects to the netlink and reads +a series of uevents; for every uevent it reads, it performs actions according to its configuration file. Actions can be inserting a kernel module, creating or modifying device entries in <tt>/dev</tt>, etc. @@ -36,35 +36,29 @@ The differences between mdevd and mdev are: <ul> <li> mdev needs to be registered as a hotplug manager and the kernel spawns an instance of mdev per uevent; for every uevent, -mdev has to parse its configuration file. By contrast, there -is only one instance of mdevd, reading a series of uevents and +mdev has to parse its configuration file. By contrast, mdevd is +a daemon: it's long-lived, and there is only one instance, +reading a series of uevents and performing actions without forking; the configuration file is read and parsed only once. </li> - <li> mdevd reads uevents on its stdin. It is not suitable as -a hotplug manager, and it does not connect to the netlink itself -either. It is meant to be used in conjunction with -<a href="mdevd-netlink.html">mdevd-netlink</a>, which reads -uevents from the netlink, or with -<a href="mdevd-coldplug.html">mdevd-coldplug</a>, which generates -coldplug uevents. </li> </ul> <h2> Interface </h2> <pre> - mdevd [ -v <em>verbosity</em> ] [ -f <em>conffile</em> ] [ -n ] [ -s <em>slashsys</em> ] [ -d <em>slashdev</em> ] [ -F <em>fwbase</em> ] + mdevd [ -v <em>verbosity</em> ] [ -D <em>notif</em> ] [ -b <em>kbufsz</em> ] [ -f <em>conffile</em> ] [ -n ] [ -s <em>slashsys</em> ] [ -d <em>slashdev</em> ] [ -F <em>fwbase</em> ] </pre> <ul> <li> mdevd reads and parses its configuration file <tt>/etc/mdev.conf</tt>. </li> - <li> It then reads its stdin, waiting for uevents. - <li> It exits when the stream of uevents ends. (EOF on stdin.) </li> + <li> It then connects to the netlink and reads from it, waiting for uevents. + <li> It exits 0 on a SIGTERM. </li> </ul> <h2> Exit codes </h2> <ul> - <li> 0: EOF read on standard input </li> + <li> 0: SIGTERM received, clean exit </li> <li> 1: received an invalid event </li> <li> 2: syntax error in the configuration file </li> <li> 100: wrong usage </li> @@ -79,6 +73,7 @@ coldplug uevents. </li> <ul> <li> SIGHUP: re-read the configuration file </li> + <li> SIGTERM: exit as soon as possible </li> </ul> <h2> Options </h2> @@ -87,6 +82,17 @@ coldplug uevents. </li> <li> <tt>-v</tt> <em>verbosity</em> : be more or less verbose. Default verbosity is 1. 0 will only print fatal error messages, 3 or more is seriously verbose debugging. </li> + <li> <tt>-D</tt> <em>notif</em> : when ready +(actually listening to the netlink), +write a newline to file descriptor <em>notif</em> then close it. +This allows mdevd to use the +<a href="//skarnet.org/software/s6/notifywhenup.html">s6 mechanism to notify +readiness</a>. <em>notif</em> cannot be lesser than 3. +If this option is not given, no readiness notification is sent. </li> + <li> <tt>-b</tt> <em>kbufsz</em> : try and reserve a kernel buffer of +<em>kbufsz</em> bytes for the netlink queue. Too large a buffer wastes kernel memory; +too small a buffer risks losing events. The default is 65536 (which is reasonable +for average systems). </li> <li> <tt>-n</tt> : dry run. mdevd will not create or delete device nodes, and it will not spawn commands. Instead, it will print to stdout the actions it would have performed. </li> @@ -121,14 +127,6 @@ nothing else. <h2> Notes </h2> <ul> - <li> Strictly speaking, mdevd is a short-lived program: it has -a normal exit condition, which is when it receives EOF on its stdin. -That allows it to work as a coldplug manager when paired with -<a href="mdevd-coldplug.html">mdevd-coldplug</a>. </li> - <li> However, when paired with <a href="mdevd-netlink.html">mdevd-netlink</a>, -it acts as a daemon, because mdev-netlink normally never exits until -the end of the machine lifetime and never closes its stdout, so -mdevd's stdin never receives EOF. </li> <li> The <tt>examples/</tt> subdirectory of the mdevd package contains examples on how to run mdevd under various init systems / supervisors. </li> </ul> |