[PATCH] Refuse to start bridging with network root filesystem

[Mark McLoughlin <markmc@redhat.com>]

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Hi,
	Since setting up bridging involves bringing down the network interface,
bridging clearly isn't compatible with the likes of NFS or iSCSI root.

	The attached patch makes network-bridge try to detect either of these
conditions and refuse to start, logging an error to syslog.

  Signed-off-by: Mark McLoughlin <markmc@redhat.com>

Thanks,
Mark.

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diff -r 3f76b2f76c2a tools/examples/network-bridge
--- a/tools/examples/network-bridge	Mon Jun 25 16:52:39 2007 +0100
+++ b/tools/examples/network-bridge	Tue Jun 26 12:41:09 2007 +0100
@@ -172,9 +172,21 @@ show_status () {
     echo '============================================================'
 }
 
+is_network_root () {
+    local rootfs=$(awk '{ if ($1 !~ /^[ \t]*#/ && $2 == "/") { print $3; }}' /etc/mtab)
+    local rootopts=$(awk '{ if ($1 !~ /^[ \t]*#/ && $2 == "/") { print $4; }}' /etc/mtab)
+
+    [[ "$rootfs" =~ "^nfs" ]] || [[ "$rootopts" =~ "_netdev" ]] && return 0 || return 1
+}
+
 op_start () {
     if [ "${bridge}" = "null" ] ; then
 	return
+    fi
+
+    if is_network_root ; then
+        [ -x /usr/bin/logger ] && /usr/bin/logger "network-bridge: bridging not supported on network root; not starting"
+        return
     fi
 
     if link_exists "$pdev"; then

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