diff options
Diffstat (limited to 'doc/s6-linux-init-maker.html')
| -rw-r--r-- | doc/s6-linux-init-maker.html | 63 |
1 files changed, 55 insertions, 8 deletions
diff --git a/doc/s6-linux-init-maker.html b/doc/s6-linux-init-maker.html index cdf617e..530cd41 100644 --- a/doc/s6-linux-init-maker.html +++ b/doc/s6-linux-init-maker.html @@ -49,6 +49,7 @@ machine</em> - else the scripts will crash. [ -u <em>log_user</em> ] \ [ -g <em>early_getty</em> ] \ [ -2 <em>stage2</em> ] \ + [ -r ] \ [ -3 <em>stage3</em> ] \ [ -p <em>initial_path</em> ] \ [ -m <em>initial_umask</em> ] \ @@ -74,7 +75,7 @@ declared as <em>basedir</em>. Be careful: it contains fifos, files with precise uid/gid permissions, and files with non-standard access rights, so be sure to copy it verbatim. The <a href="http://skarnet.org/software/s6-portable-utils/s6-hiercopy.html">s6-hiercopy</a> -tool can do it, as well as the GNU or busybox <tt>cp -a</tt> command. +tool can do it, as well as the GNU or busybox <tt>cp -a</tt> or <tt>mv</tt> commands. </p> <p> @@ -133,11 +134,10 @@ system. When <em>stage2</em> is executed, the machine state is as follows: <ul> <li> <em>stage2</em>'s working directory is <tt>/</tt> and its stdin -is <tt>/dev/null</tt>. <em>stage2</em>'s -stdout and stderr both point to the pipe to the catch-all logger, so -unless redirected, <em>stage2</em>'s output will be logged into the -<tt><em>tmpfsdir/uncaught-logs</em></tt> directory. </li> - <li> The system has a valid device directory mounted on <tt>/dev</tt>. +is <tt>/dev/null</tt>. Its +stdout and stderr both point either to <tt>/dev/console</tt> or to the pipe +to the catch-all logger, depending on the <tt>-r</tt> option. </li> + <li> The system has a valid device directory mounted on <tt>/dev</tt>. </li> <li> Depending on the kernel boot command line, the root filesystem may be in read-only mode. </li> <li> There is a tmpfs available for root only in <em>tmpfsdir</em>. </li> @@ -227,6 +227,14 @@ the location of the stage 2 script that will be run when the system has an operational supervision tree. It must be absolute. Default is <strong><tt>/etc/rc.init</tt></strong>. </li> <p /> + <li> <tt>-r</tt> : redirect. By default, <em>stage2</em> is +run with stdout and stderr pointing to <tt>/dev/console</tt>, so that +users can see what init scripts print. However, it may conflict +with an early getty, or be undesirable for other reasons. The +<tt>-r</tt> option redirects <em>stage2</em>'s stdout and stderr +to the catch-all logger, so the output will be made available +in the <tt><em>tmpfsdir</em>/uncaught-logs</tt> directory. </li> <p /> + <li> <tt>-3</tt> <em>stage3</em> : <em>stage3</em> is the location of the stage 3 script that will be run at the end of the machine lifetime, when s6-svscan is told to terminate. @@ -235,8 +243,14 @@ It must be absolute. Default is <li> <tt>-p</tt> <em>initial_path</em> : the value to set the PATH environment variable to, for all the starting processes. -This will be done as early as possible in <em>stage1</em>. Default is -the value that has been compiled in +This will be done as early as possible in <em>stage1</em>. It is +absolutely necessary for +<a href="http://skarnet.org/software/execline/">execline</a>, +<a href="http://skarnet.org/software/s6/">s6</a>, +<a href="http://skarnet.org/software/s6-portable-utils/">s6-portable-utils</a> and +<a href="http://skarnet.org/software/s6-linux-utils/">s6-linux-utils</a> +binaries to be accessible via <em>initial_path</em>, else the machine +will not boot. Default is the value that has been compiled in <a href="http://skarnet.org/software/skalibs/">skalibs</a> via the <tt>--with-default-path</tt> configure option, i.e. by default <strong><tt>/usr/bin:/bin</tt></strong>. </li> <p /> @@ -272,5 +286,38 @@ The TZ variable, for instance, is a good candidate to be set in the global environment. </li> <p /> </ul> +<h2> Notes </h2> + +<p> + The difficult parts of +<a href="http://skarnet.org/software/s6/s6-svscan-1.html">running +s6-svscan as process 1</a> are: +</p> + +<ul> + <li> The fact that the supervision tree requires writable directories, +so in order to accommodate read-only root filesystems, there needs to +be a tmpfs mounted before s6-svscan is run. </li> + <li> The catch-22 coming for the need to redirect the supervision +tree's output away from <tt>/dev/console</tt> (which is fine for a +first process invocation but impractical for log management of a +whole process tree) and into a logger that is itself managed by the +supervision tree it's reading data from. </li> +</ul> + +<p> + The main benefit of s6-linux-init-maker is that it automates those +parts. This means that it has been designed for <em>real hardware</em> +where the above issues apply. + If you are building an init system for a +virtual machine, a container, or anything similar that does not +have the <tt>/dev/console</tt> issue or the read-only rootfs issue, +you will probably not reap much benefit from using s6-linux-init-maker: +you could probably invoke +<a href="http://skarnet.org/software/s6/s6-svscan.html">s6-svscan</a> +directly as your process 1, or build a script by hand, which +would result in a simpler init with less dependencies. +</p> + </body> </html> |