=== modified file 'debian/changelog'
--- debian/changelog	2011-09-23 15:26:33 +0000
+++ debian/changelog	2011-09-23 16:08:18 +0000
@@ -1,3 +1,9 @@
+isc-dhcp (4.1.1-P1-17ubuntu11) UNRELEASED; urgency=low
+
+  * debian/dhclient-script.linux: fix for read-only /etc (LP: #857524)
+
+ -- Scott Moser <smoser@ubuntu.com>  Fri, 23 Sep 2011 12:07:24 -0400
+
 isc-dhcp (4.1.1-P1-17ubuntu10) oneiric; urgency=low
 
   * make sure writing of /etc/resolv.conf actually waits until the file is 

=== modified file 'debian/dhclient-script.linux'
--- debian/dhclient-script.linux	2011-09-23 15:26:18 +0000
+++ debian/dhclient-script.linux	2011-09-23 16:07:04 +0000
@@ -12,8 +12,9 @@
 
 # The alias handling in here probably still sucks. -mdz
 
-# wait for /etc/resolv.conf to become writable
+# wait for given file to be writable
 wait_for_rw() {
+    local file=$1
     # Find out whether we are going to mount / rw
     exec 9>&0 </etc/fstab
     rootmode=rw
@@ -27,9 +28,9 @@
      done
      exec 0>&9 9>&-
  
-    # Wait for /etc/resolv.conf to become writable
+    # Wait for $file to become writable
     if [ "$rootmode" = "rw" ]; then
-        while ! { : >> /etc/resolv.conf; } 2>/dev/null; do
+        while ! { : >> "$file"; } 2>/dev/null; do
             sleep 0.1
         done
     fi
@@ -37,17 +38,19 @@
 
 # update /etc/resolv.conf based on received values
 make_resolv_conf() {
-    local new_resolv_conf
+    local old_ns=""
+    [ -e /etc/resolv.conf ] &&
+        old_ns=$(sed -n \
+            /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p /etc/resolv.conf)
 
     # DHCPv4
     if [ -n "$new_domain_search" ] || [ -n "$new_domain_name" ] ||
        [ -n "$new_domain_name_servers" ]; then
-        wait_for_rw
-        new_resolv_conf=/etc/resolv.conf.dhclient-new
-        rm -f $new_resolv_conf
+        wait_for_rw /etc/resolv.conf
 
+        {
         if [ -n "$new_domain_name" ]; then
-            echo domain ${new_domain_name%% *} >>$new_resolv_conf
+            echo domain ${new_domain_name%% *}
         fi
 
         if [ -n "$new_domain_search" ]; then
@@ -63,43 +66,36 @@
                     new_domain_search="$new_domain_name $new_domain_search"
                 fi
             fi
-            echo "search ${new_domain_search}" >> $new_resolv_conf
+            echo "search ${new_domain_search}"
         elif [ -n "$new_domain_name" ]; then
-            echo "search ${new_domain_name}" >> $new_resolv_conf
+            echo "search ${new_domain_name}"
         fi
 
         if [ -n "$new_domain_name_servers" ]; then
             for nameserver in $new_domain_name_servers; do
-                echo nameserver $nameserver >>$new_resolv_conf
+                echo nameserver $nameserver
             done
-        else # keep 'old' nameservers
-            sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p /etc/resolv.conf >>$new_resolv_conf
+        elif [ -n "$old_ns" ]; then # keep 'old' nameservers
+            echo "$old_ns"
         fi
-
-        chown --reference=/etc/resolv.conf $new_resolv_conf
-        chmod --reference=/etc/resolv.conf $new_resolv_conf
-        mv -f $new_resolv_conf /etc/resolv.conf
+        } > /etc/resolv.conf
     # DHCPv6
     elif [ -n "$new_dhcp6_domain_search" ] || [ -n "$new_dhcp6_name_servers" ]; then
-        wait_for_rw
-        new_resolv_conf=/etc/resolv.conf.dhclient-new
-        rm -f $new_resolv_conf
+        wait_for_rw /etc/resolv.conf
 
+        {
         if [ -n "$new_dhcp6_domain_search" ]; then
-            echo "search ${new_dhcp6_domain_search}" >> $new_resolv_conf
+            echo "search ${new_dhcp6_domain_search}"
         fi
 
         if [ -n "$new_dhcp6_name_servers" ]; then
             for nameserver in $new_dhcp6_name_servers; do
-                echo nameserver $nameserver >>$new_resolv_conf
+                echo nameserver $nameserver
             done
-        else # keep 'old' nameservers
-            sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p /etc/resolv.conf >>$new_resolv_conf
+        elif [ -n "$old_ns" ]; then # keep 'old' nameservers
+            echo "$old_ns"
         fi
-
-        chown --reference=/etc/resolv.conf $new_resolv_conf
-        chmod --reference=/etc/resolv.conf $new_resolv_conf
-        mv -f $new_resolv_conf /etc/resolv.conf
+        } > /etc/resolv.conf
     fi
 }