Add support for "first boot" rc.d scripts. [1]

These scripts, containing
# KEYWORD: firstboot
will only be run if a sentinel file (default: /firstboot, configurable
via the rc.conf ${firstboot_sentinel} variable) exists; this sentinel
file will be deleted at the end of the boot process.

Scripts can request that the system reboot after the first boot by
creating the file ${firstboot_sentinel}-reboot.

This functionality is expected to be useful for embedded systems and
virtual machine images, where it may be desirable to
(a) download and install updates which became available between when
the image was created and when it was "turned on";
(b) download and install packages which may be newer than those
which were available when the image was created;
(c) install packages which run binaries during their install process,
bypassing the problem of cross-architecture installs;
(d) resize filesystems to match the disk onto which a VM image was
installed;
(e) perform initialization tasks relevant to cloud systems (e.g.,
Amazon's Elastic Compute Cloud);
and likely to perform many other one-time initialization functions.

Document this new functionality in rc.conf(5) and rc(8). [2]

Reviewed by:	freebsd-current, freebsd-rc [1]
Reviewed by:	Warren Block [2]
MFC after:	3 days

1 files changed, 20 insertions, 1 deletions

diff --git a/share/man/man8/rc.8 b/share/man/man8/rc.8
index 32d0ade..cfeb0e6 100644
--- a/share/man/man8/rc.8
+++ b/share/man/man8/rc.8
@@ -35,7 +35,7 @@
 .\"     @(#)rc.8	8.2 (Berkeley) 12/11/93
 .\" $FreeBSD$
 .\"
-.Dd September 23, 2013
+.Dd October 19, 2013
 .Dt RC 8
 .Os
 .Sh NAME
@@ -129,6 +129,13 @@ and add
 (only allow vnet-enabled jails) to the list of KEYWORDS to skip in
 .Xr rcorder 8 .
 .It
+If the file
+.Va ${firstboot_sentinel}
+does not exist, add
+.Dq Li firstboot
+to the list of KEYWORDS to skip in
+.Xr rcorder 8 .
+.It
 Invoke
 .Xr rcorder 8
 to order the files in
@@ -156,6 +163,11 @@ Stop processing when the script that is the value of the
 .Va $early_late_divider
 has been run.
 .It
+Check again to see if the file
+.Va ${firstboot_sentinel}
+exists (in case it is located on a newly mounted file system)
+and adjust the list of KEYWORDs to skip appropriately.
+.It
 Re-run
 .Xr rcorder 8 ,
 this time including the scripts in the
@@ -164,6 +176,13 @@ directories.
 Ignore everything up to the
 .Va $early_late_divider ,
 then start executing the scripts as described above.
+.It
+If the file
+.Va ${firstboot_sentinel}
+exists, delete it.
+If the file
+.Va ${firstboot_sentinel}-reboot
+also exists (because it was created by a script), then delete it and reboot.
 .El
 .Ss Operation of Nm rc.shutdown
 .Bl -enum