>Number:         36508
>Category:       misc
>Synopsis:       Init scripts to enable mounting from read only filesystems
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    misc-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Mon Jun 18 22:00:01 +0000 2007
>Originator:     Adam Hoka
>Release:        NetBSD-4
>Organization:
>Environment:
>Description:
These init scripts are ported from FreeBSD and they make an automatic check wheter the /var and /tmp filesystems are writable at the pont they should be. If they are not, the script mounts a writeable ramdisk device to the read-only directory. The script also populates the /var ramdisk using the mtree tool.

The ramdisks can use both mfs and tmpfs. The tmpfs is the default setting, but it can be overridden in rc.conf, as the size of the ramdisk drives.
The whole scripts also can be disabled or forced in rc.conf.

This let the system to function with only a few limits without a writable filesystem out of the box.
>How-To-Repeat:
Try to boot the system from from a read-only device, without setting ramdisks for /var and/or /tmp in fstab, nor through any other script.
The system won`t be able to work properly.
>Fix:
--- /etc/defaults/rc.conf	2006-10-07 18:50:34.000000000 +0200
+++ /etc/defaults/rc.conf	2007-06-18 21:20:00.000000000 +0200
@@ -321,3 +321,15 @@
 veriexec=NO
 veriexec_strict=0
 veriexec_verbose=0
+
+# Settings for automatic ramdisk mount, by default the system will mount
+# a tmpfs ramdisk for /var and /tmp if they are on non-writable area.
+#
+tmpmfs="AUTO"		# Set to YES to always create an mfs /tmp, NO to never
+tmpmfs_type="tmpfs"	# You can set it to mfs or tmpfs
+tmpsize="20m"		# Size of mfs /tmp if created
+tmpmfs_flags=""	# Extra mdmfs options for the mfs /tmp
+varmfs="AUTO"		# Set to YES to always create an mfs /var, NO to never
+varmfs_type="tmpfs"	# You can set it to mfs or tmpfs
+varsize="32m"		# Size of mfs /var if created
+varmfs_flags=""	# Extra mount options for the mfs /var


--- /dev/null	2007-06-18 20:03:03.000000000 +0200
+++ /etc/rc.d/tmp	2007-06-18 21:20:01.000000000 +0200
@@ -0,0 +1,84 @@
+#!/bin/sh
+#
+# Copyright (c) 1999  Matt Dillon
+# Copyright (c) 2007  Adam Hoka
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+# $FreeBSD: /repoman/r/ncvs/src/etc/rc.d/tmp,v 1.38 2007/05/24 05:54:37 rse Exp $
+#
+
+# PROVIDE: tmp
+# REQUIRE: mountcritremote
+# BEFORE: SERVERS
+
+. /etc/rc.subr
+
+name="tmp"
+
+load_rc_config $name
+
+# If we do not have a writable /tmp, create a memory
+# filesystem for /tmp.  If /tmp is a symlink (e.g. to /var/tmp,
+# then it should already be writable).
+# We invoke the whole script before SERVER, because they may need to
+# write to /tmp.
+
+mount_tmp_ramdisk()
+{               
+case "${tmpmfs_type}" in
+tmpfs)          
+        mount_tmpfs -s ${tmpsize} ${tmpmfs_flags} tmpfs /tmp
+	;;      
+mfs)                    
+	mount_mfs -s ${tmpsize} ${tmpmfs_flags} swap /tmp
+	;;              
+*)              
+	echo "Warning: tmpmfs_type is not properly set, falling back to tmpfs"
+        mount_tmpfs -s ${tmpsize} ${tmpmfs_flags} tmpfs /tmp
+	;;
+esac
+} 
+
+case "${tmpmfs}" in
+[Yy][Ee][Ss])
+	mount_tmp_ramdisk
+	chmod 01777 /tmp
+	;;
+[Nn][Oo])
+	;;
+*)
+	if /bin/mkdir -p /tmp/.diskless 2> /dev/null; then
+		rmdir /tmp/.diskless
+	else
+		if [ -h /tmp ]; then
+			echo "*** /tmp is a symlink to a non-writable area!"
+			echo "dropping into shell, ^D to continue anyway."
+			/bin/sh
+		else
+			mount_tmp_ramdisk
+			chmod 01777 /tmp
+		fi
+	fi
+	;;
+esac


--- /dev/null	2007-06-18 20:03:03.000000000 +0200
+++ /etc/rc.d/var	2007-06-18 21:20:01.000000000 +0200
@@ -0,0 +1,133 @@
+#!/bin/sh
+#
+# Copyright (c) 1999  Matt Dillon
+# Copyright (c) 2007  Adam Hoka
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+# $FreeBSD: /repoman/r/ncvs/src/etc/rc.d/var,v 1.43 2007/05/24 05:54:37 rse Exp $
+#
+
+# PROVIDE: var
+# REQUIRE: mountcritlocal
+# BEFORE: dhclient
+
+$_rc_subr_loaded . /etc/rc.subr
+
+name="var"
+load_rc_config $name
+
+populate_var()
+{
+	(mkdir -p /var/mtree_root && mtree -deU -f /etc/mtree/NetBSD.dist -p /var/mtree_root > /dev/null && mv /var/mtree_root/var/* /var && rm -rf /var/mtree_root)
+}
+
+# I made it possible to choose from using tmpfs or the legacy mfs. 
+#
+mount_var_ramdisk()
+{
+case "${varmfs_type}" in
+tmpfs)
+	mount_tmpfs -s ${varsize} ${varmfs_flags} tmpfs /var
+	;;
+mfs)
+	mount_mfs -s ${varsize} ${varmfs_flags} swap /var
+	;;
+*)
+	echo "Warning: varmfs_type is not properly set, falling back to tmpfs"
+        mount_tmpfs -s ${varsize} ${varmfs_flags} tmpfs /var
+	;;
+esac
+}
+
+# If we do not have a writable /var, create a memory filesystem for /var
+# unless told otherwise by rc.conf.  We don't have /usr yet so use mkdir
+# instead of touch to test.  We want mount to record its mounts so we
+# have to make sure /var/db exists before doing the mount -a.
+# It`s invoked before dhclient because it needs to write a leases file.
+#
+case "${varmfs}" in
+[Yy][Ee][Ss])
+	mount_var_ramdisk
+	;;
+[Nn][Oo])
+	;;
+*)
+	if /bin/mkdir -p /var/.diskless 2> /dev/null; then
+		rmdir /var/.diskless
+	else
+		mount_var_ramdisk
+	fi
+esac
+
+
+# If we have an empty looking /var, populate it, but only if we have
+# /usr available.  Hopefully, we'll eventually find a workaround, but
+# in realistic diskless setups, we're probably ok.
+#
+case "${populate_var}" in
+[Yy][Ee][Ss])
+	populate_var
+	;;
+[Nn][Oo])
+	exit 0
+	;;
+*)
+	if [ -d /var/run -a -d /var/db ] ; then
+		true
+	elif [ -x /usr/sbin/mtree ] ; then
+		populate_var
+	else
+		# We need mtree to populate /var so try mounting /usr.
+		# If this does not work, we can not boot so it is OK to
+		# try to mount out of order.
+		#
+		mount /usr
+		if [ ! -x /usr/sbin/mtree ] ; then
+			exit 1
+		else
+			populate_var
+		fi
+	fi
+	;;
+esac
+
+# Make sure we have /var/log/lastlog,  /var/log/wtmp
+# /var/log/lastlogx and /var/log/wtmpx files
+#
+if [ ! -f /var/log/lastlog ]; then
+	cp /dev/null /var/log/lastlog
+	chmod 644 /var/log/lastlog
+fi
+if [ ! -f /var/log/wtmp ]; then
+	cp /dev/null /var/log/wtmp
+	chmod 644 /var/log/wtmp
+fi
+if [ ! -f /var/log/lastlogx ]; then
+	cp /dev/null /var/log/lastlogx
+	chmod 644 /var/log/lastlogx
+fi
+if [ ! -f /var/log/wtmpx ]; then
+	cp /dev/null /var/log/wtmpx
+	chmod 644 /var/log/wtmpx
+fi