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, 22 insertions, 2 deletions

diff --git a/etc/rc b/etc/rc
index 59dece8..fd5ff85 100644
--- a/etc/rc
+++ b/etc/rc
@@ -82,10 +82,15 @@ if [ `/sbin/sysctl -n security.jail.jailed` -eq 1 ]; then
 	fi
 fi
 
+# If the firstboot sentinel doesn't exist, we want to skip firstboot scripts.
+if ! [ -e ${firstboot_sentinel} ]; then
+	skip_firstboot="-s firstboot"
+fi
+
 # Do a first pass to get everything up to $early_late_divider so that
 # we can do a second pass that includes $local_startup directories
 #
-files=`rcorder ${skip} /etc/rc.d/* 2>/dev/null`
+files=`rcorder ${skip} ${skip_firstboot} /etc/rc.d/* 2>/dev/null`
 
 _rc_elem_done=' '
 for _rc_elem in ${files}; do
@@ -107,7 +112,13 @@ case ${local_startup} in
 *)	find_local_scripts_new ;;
 esac
 
-files=`rcorder ${skip} /etc/rc.d/* ${local_rc} 2>/dev/null`
+# The firstboot sentinel might be on a newly mounted filesystem; look for it
+# again and unset skip_firstboot if we find it.
+if [ -e ${firstboot_sentinel} ]; then
+	skip_firstboot=""
+fi
+
+files=`rcorder ${skip} ${skip_firstboot} /etc/rc.d/* ${local_rc} 2>/dev/null`
 for _rc_elem in ${files}; do
 	case "$_rc_elem_done" in
 	*" $_rc_elem "*)	continue ;;
@@ -116,6 +127,15 @@ for _rc_elem in ${files}; do
 	run_rc_script ${_rc_elem} ${_boot}
 done
 
+# Remove the firstboot sentinel, and reboot if it was requested.
+if [ -e ${firstboot_sentinel} ]; then
+	rm ${firstboot_sentinel}
+	if [ -e ${firstboot_sentinel}-reboot ]; then
+		rm ${firstboot_sentinel}-reboot
+		kill -INT 1
+	fi
+fi
+
 echo ''
 date
 exit 0