Add -n and -N options to s6-l-i and s6-l-i-m

4 files changed, 82 insertions, 21 deletions

diff --git a/doc/s6-linux-init-maker.html b/doc/s6-linux-init-maker.html
index 6c52d32..02fd15d 100644
--- a/doc/s6-linux-init-maker.html
+++ b/doc/s6-linux-init-maker.html
@@ -59,6 +59,7 @@ machine</em>. If it is not the case, the system will fail to boot.
        [ -e <em>initial_envvar</em> ] ... \
        [ -q <em>finalsleeptime</em> ] \
        [ -D <em>initdefault</em> ] \
+       [ -n | -N ]
        [ -U <em>utmp_user</em> ] \
        <em>dir</em>
 </pre>
@@ -169,7 +170,7 @@ is defined. </li> <p />
  <li> <tt>-1</tt>&nbsp;: make it so that all the messages that are
 sent to the catch-all logger (i.e. all the error messages that are not
 caught by a dedicated logger, as well as the output from <em>rc.init</em>,
-<em>runlevel</em> and <em>rc.shutdown</em>,
+<em>runlevel</em> and <em>rc.shutdown</em>)
 are also copied to <tt>/dev/console</tt>. (Timestamps are not
 copied to <tt>/dev/console</tt>.) This is generally useful to
 debug a system at a glance, but if a failing program keeps sending
@@ -264,6 +265,36 @@ sysvinit behaviour) or <tt>default</tt> (OpenRC behaviour). Default is
 command line, it will be interpreted as the runlevel to boot the system
 on, and will override the default given here. </li> <p />
 
+ <li> <tt>-n</tt>&nbsp;: at boot time, assume that a tmpfs is already
+present on <tt>/run</tt> (or the argument that was given to the
+<tt>--tmpfsdir</tt> configure option at build time) and that its
+contents are essential. Instead of unmounting <tt>/run</tt> then
+mounting a tmpfs on it, <a href="s6-linux-init.html">s6-linux-init</a>
+will simply remount <tt>/run</tt>. This option is useful when
+s6-linux-init is used on a distribution that imposes its initramfs
+and said initramfs writes data to <tt>/run</tt> that is then used
+by the distribution's initialization scripts. (An initramfs should
+normally be transparent and leave no trace in the filesystem;
+unfortunately, a lot of distributions do not care.) By default,
+<tt>/run</tt> will be unmounted at boot time (just in case), and
+then a tmpfs will be mounted on it. <strong>Do not</strong> use
+this option if you are not sure: failure to remount <tt>/run</tt>
+will cause init to die and the kernel to panic. This option is
+incompatible with the <tt>-N</tt> option. </li> <p />
+
+ <li> <tt>-N</tt>&nbsp;: at boot time, do not perform
+mounting/unmounting/remounting on <tt>/run</tt> (or the <em>tmpfsdir</em>
+declared at build time) <strong>at all</strong>. By default,
+a tmpfs is mounted on <tt>/run</tt> at boot time. This option is
+useful when s6-linux-init is used to boot on an initramfs that
+will remain the de facto rootfs of the system (which is the case
+for instance in certain live CDs or certain embedded devices), in
+which case the rootfs is already read-write and in RAM and mounting
+an additional tmpfs is unnecessary. <strong>Do not</strong> use this
+option if your rootfs is read-only: failure to write to <tt>/run</tt>
+will cause init to die and the kernel to panic. This option is
+incompatible with the <tt>-n</tt> option. </li> <p />
+
  <li> <tt>-U</tt>&nbsp;<em>utmp_user</em>&nbsp;: this option is only
 available when the s6-linux-init package has been built with the
 <tt>--enable-utmps</tt> configure option, that enables support for the
diff --git a/doc/s6-linux-init.html b/doc/s6-linux-init.html
index 31014d6..f57adae 100644
--- a/doc/s6-linux-init.html
+++ b/doc/s6-linux-init.html
@@ -27,7 +27,7 @@ and execs into <a href="//skarnet.org/software/s6/s6-svscan.html">s6-svscan</a>.
 <h2> Interface </h2>
 
 <pre>
-     s6-linux-init [ -c <em>basedir</em> ] [ -p <em>initial_path</em> ] [ -s <em>env_store</em> ] [ -m <em>umask</em> ] [ -d <em>dev_style</em> ] [ -D <em>initdefault</em> ] [ <em>args...</em> ]
+     s6-linux-init [ -c <em>basedir</em> ] [ -p <em>initial_path</em> ] [ -s <em>env_store</em> ] [ -m <em>umask</em> ] [ -d <em>dev_style</em> ] [ -D <em>initdefault</em> ] [ -n | -N ] [ <em>args...</em> ]
 </pre>
 
 <ul>
@@ -57,14 +57,16 @@ the PATH environment variable. </li>
  <li> <tt>-s</tt>&nbsp;<em>env_store</em>&nbsp;: the place where to dump
 kernel environment variables. </li>
  <li> <tt>-m</tt>&nbsp;<em>initial_umask</em>&nbsp;: the initial file umask. </li>
- <li> <tt>-d</tt>&nbsp;<em>dev_style</em>&nbsp;: how <tt>/dev</tt> is
-handled on this system. 0 means a static <tt>/dev</tt>, 1 means
-devtmpfs but not automounted by the kernel at boot time, and 2 means
-devtmpfs automounted by the kernel at boot time. </li>
+ <li> <tt>-d</tt>&nbsp;<em>slashdev</em>&nbsp;: mount a devtmpfs on
+<em>slashdev</em>. By default, no such mount is performed - it is assumed
+that a devtmpfs is automounted on <tt>/dev</tt> at boot time by the kernel. </li>
  <li> <tt>-D</tt>&nbsp;<em>initdefault</em>&nbsp;: the initial runlevel
 to boot to, if it isn't overridden by the kernel command line.
 This is only given as a first argument to <em>rc.init</em>.
 Default is <tt>default</tt>. </li>
+ <li> <tt>-n</tt>&nbsp;: instead of unmounting <tt>/run</tt> and mounting
+a tmpfs on it, just remount <tt>/run</tt>. </li>
+ <li> <tt>-N</tt>&nbsp;: do not touch <tt>/run</tt> at all. </li>
 </ul>
 
 <h2> Early preparation </h2>
@@ -79,12 +81,13 @@ operations:
  <li> It chdirs to <tt>/</tt>. </li>
  <li> It sets the umask to <em>initial_umask</em>. </li>
  <li> It becomes a session leader. </li>
- <li> It mounts a devtmpfs on <tt>/dev</tt>, if necessary. </li>
+ <li> It mounts a devtmpfs on <em>slashdev</em>, if requested. </li>
  <li> It uses <tt>/dev/null</tt> as its stdin (instead of <tt>/dev/console</tt>).
 <tt>/dev/console</tt> is still used, for now, as stdout and stderr. </li>
  <li> It unmounts <tt>/run</tt> (or the directory you have given to the
-<tt>--tmpfsdir</tt> configure option at package build time), just in case. </li>
- <li> It creates a tmpfs on <tt>/run</tt> (or your chosen <em>tmpfsdir</em>). </li>
+<tt>--tmpfsdir</tt> configure option at package build time), just in case;
+then it creates a tmpfs on it. Alternatively, it remounts <tt>/run</tt>,
+or does not touch it at all. </li>
  <li> It copies the whole <tt><em>basedir</em>/run-image</tt> hierarchy to
 <tt>/run</tt> (or your chosen tmpfsdir). </li>
  <li> It reads the initial environment from <tt><em>basedir</em>/env</tt>. </li>
diff --git a/src/init/s6-linux-init-maker.c b/src/init/s6-linux-init-maker.c
index 434e29f..1005811 100644
--- a/src/init/s6-linux-init-maker.c
+++ b/src/init/s6-linux-init-maker.c
@@ -28,12 +28,12 @@
 
 #ifdef S6_LINUX_INIT_UTMPD_PATH
 # include <utmps/config.h>
-# define USAGE "s6-linux-init-maker [ -c basedir ] [ -u log_user ] [ -G early_getty_cmd ] [ -1 ] [ -L ] [ -p initial_path ] [ -m initial_umask ] [ -t timestamp_style ] [ -d slashdev ] [ -s env_store ] [ -e initial_envvar ... ] [ -q default_grace_time ] [ -D initdefault ] [ -U utmp_user ] dir"
-# define OPTION_STRING "c:u:G:1Lp:m:t:d:s:e:E:q:U:D:"
+# define USAGE "s6-linux-init-maker [ -c basedir ] [ -u log_user ] [ -G early_getty_cmd ] [ -1 ] [ -L ] [ -p initial_path ] [ -m initial_umask ] [ -t timestamp_style ] [ -d slashdev ] [ -s env_store ] [ -e initial_envvar ... ] [ -q default_grace_time ] [ -D initdefault ] [ -n | -N ] [ -U utmp_user ] dir"
+# define OPTION_STRING "c:u:G:1Lp:m:t:d:s:e:E:q:D:nNU:"
 # define UTMPS_DIR "utmps"
 #else
-# define USAGE "s6-linux-init-maker [ -c basedir ] [ -u log_user ] [ -G early_getty_cmd ] [ -1 ] [ -L ] [ -p initial_path ] [ -m initial_umask ] [ -t timestamp_style ] [ -d slashdev ] [ -s env_store ] [ -e initial_envvar ... ] [ -q default_grace_time ] [ -D initdefault ] dir"
-# define OPTION_STRING "c:u:G:1Lp:m:t:d:s:e:E:q:D:"
+# define USAGE "s6-linux-init-maker [ -c basedir ] [ -u log_user ] [ -G early_getty_cmd ] [ -1 ] [ -L ] [ -p initial_path ] [ -m initial_umask ] [ -t timestamp_style ] [ -d slashdev ] [ -s env_store ] [ -e initial_envvar ... ] [ -q default_grace_time ] [ -D initdefault ] [ -n | -N ] dir"
+# define OPTION_STRING "c:u:G:1Lp:m:t:d:s:e:E:q:D:nN"
 #endif
 
 #define dieusage() strerr_dieusage(100, USAGE)
@@ -51,6 +51,7 @@ static char const *initdefault = 0 ;
 static unsigned int initial_umask = 0022 ;
 static unsigned int timestamp_style = 1 ;
 static unsigned int finalsleep = 3000 ;
+static int mounttype = 1 ;
 static int console = 0 ;
 static int logouthookd = 0 ;
 
@@ -233,6 +234,15 @@ static inline int stage1_script (buffer *b, char const *data)
     if (buffer_put(b, satmp.s + sabase, satmp.len - sabase) < 0) goto err ;
     satmp.len = sabase ;
   }
+  if (mounttype == 2)
+  {
+    if (buffer_puts(b, " -n") < 0) return 0 ;
+  }
+  else if (!mounttype)
+  {
+    if (buffer_puts(b, " -N") < 0) return 0 ;
+  }
+
   if (buffer_puts(b, "\n") < 0) return 0 ;
   (void)data ;
   return 1 ;
@@ -575,6 +585,8 @@ int main (int argc, char const *const *argv, char const *const *envp)
         case 'e' : if (!stralloc_catb(&satmp, l.arg, strlen(l.arg) + 1)) dienomem() ; break ;
         case 'q' : if (!uint0_scan(l.arg, &finalsleep)) dieusage() ; break ;
         case 'D' : initdefault = l.arg ; break ;
+        case 'n' : mounttype = 2 ; break ;
+        case 'N' : mounttype = 0 ; break ;
 #ifdef S6_LINUX_INIT_UTMPD_PATH
         case 'U' : utmp_user = l.arg ; break ;
 #endif
diff --git a/src/init/s6-linux-init.c b/src/init/s6-linux-init.c
index b6113a9..e322fa4 100644
--- a/src/init/s6-linux-init.c
+++ b/src/init/s6-linux-init.c
@@ -23,7 +23,7 @@
 #include "defaults.h"
 #include "initctl.h"
 
-#define USAGE "s6-linux-init [ -c basedir ] [ -p initpath ] [ -s envdumpdir ] [ -m umask ] [ -d devtmpfs ] [ -D initdefault ]"
+#define USAGE "s6-linux-init [ -c basedir ] [ -p initpath ] [ -s envdumpdir ] [ -m umask ] [ -d devtmpfs ] [ -D initdefault ] [ -n | -N ]"
 #define dieusage() strerr_dieusage(100, USAGE)
 
 #define BANNER "\n  s6-linux-init version " S6_LINUX_INIT_VERSION "\n\n"
@@ -68,6 +68,7 @@ int main (int argc, char const **argv, char const *const *envp)
   char const *slashdev = 0 ;
   char const *envdumpdir = 0 ;
   char const *initdefault = "default" ;
+  int mounttype = 1 ;
   stralloc envmodifs = STRALLOC_ZERO ;
   PROG = "s6-linux-init" ;
 
@@ -82,7 +83,7 @@ int main (int argc, char const **argv, char const *const *envp)
     subgetopt_t l = SUBGETOPT_ZERO ;
     for (;;)
     {
-      int opt = subgetopt_r(argc, argv, "c:p:s:m:d:D:", &l) ;
+      int opt = subgetopt_r(argc, argv, "c:p:s:m:d:D:nN", &l) ;
       if (opt == -1) break ;
       switch (opt)
       {
@@ -92,6 +93,8 @@ int main (int argc, char const **argv, char const *const *envp)
         case 'm' : if (!uint0_oscan(l.arg, &mask)) dieusage() ; break ;
         case 'd' : slashdev = l.arg ; break ;
         case 'D' : initdefault = l.arg ; break ;
+        case 'n' : mounttype = 2 ; break ;
+        case 'N' : mounttype = 0 ; break ;
         default : dieusage() ;
       }
     }
@@ -121,14 +124,26 @@ int main (int argc, char const **argv, char const *const *envp)
      || fd_move(2, 0) == -1) return 111 ;
   }
   if (open("/dev/null", O_RDONLY)) strerr_diefu1sys(111, "open /dev/null") ;
-  
-  if (umount(S6_LINUX_INIT_TMPFS) == -1)
+
+  if (mounttype)
   {
-    if (errno != EINVAL)
-      strerr_warnwu1sys("umount " S6_LINUX_INIT_TMPFS) ;
+    if (mounttype == 2)
+    {
+      if (mount("tmpfs", S6_LINUX_INIT_TMPFS, "tmpfs", MS_REMOUNT | MS_NODEV | MS_NOSUID, "mode=0755") == -1)
+        strerr_diefu1sys(111, "remount " S6_LINUX_INIT_TMPFS) ;
+    }
+    else
+    {
+      if (umount(S6_LINUX_INIT_TMPFS) == -1)
+      {
+        if (errno != EINVAL)
+          strerr_warnwu1sys("umount " S6_LINUX_INIT_TMPFS) ;
+      }
+      if (mount("tmpfs", S6_LINUX_INIT_TMPFS, "tmpfs", MS_NODEV | MS_NOSUID, "mode=0755") == -1)
+        strerr_diefu1sys(111, "mount tmpfs on " S6_LINUX_INIT_TMPFS) ;
+    }
   }
-  if (mount("tmpfs", S6_LINUX_INIT_TMPFS, "tmpfs", MS_NODEV | MS_NOSUID, "mode=0755") == -1)
-    strerr_diefu1sys(111, "mount tmpfs on " S6_LINUX_INIT_TMPFS) ;
+
   {
     size_t dirlen = strlen(basedir) ;
     char fn[dirlen + 1 + (sizeof(RUNIMAGE) > sizeof(ENVSTAGE1) ? sizeof(RUNIMAGE) : sizeof(ENVSTAGE1))] ;