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Old 12-14-2009, 02:02 AM   #1
deadeyes
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Registered: Aug 2006
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/etc/resolv.conf search line depending on connected network


Hi all,

I use my laptop both at home and at my job.
At home it gives me the correct search line.
But when I am at the office I only get 1 search entry while if you boot in windows it gives you 3 (for example):
domain
domain.com
my.domain.com

So this should be in /etc/resolv.conf
search domain domain.com my.domain.com

It seems that this is not passed by the (Windows) dhcp server (Active Directory).
Is there any way that linux can detect depending on the network it is in that there are a few search domains added(for example like resolvconf does with ppp tunnels)?
 
Old 12-15-2009, 03:06 AM   #2
unSpawn
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If this is only about /etc/resolv.conf then if you use dhclient or similar DHCP client SW then it's just per-network configuration of DHCP client SW. If you want separate and automagical per network configuration then netenv, netGo, searching your distro repo or searching Freshmeat (like http://freshmeat.net/search?q=laptop...&submit=Search), Sourceforge and Nongnu should yield usable results.
 
Old 12-15-2009, 03:19 AM   #3
deadeyes
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Ok, thanks for your reply.

But I notice that these tools need "human interaction". Is it possible that the tool does recognize which search line it should use through network, netmask and gateway given by dhcpclient? Or are these only necessary when I want manual configuration.

What do you mean with SW?

Thanks in advance!

Last edited by deadeyes; 12-15-2009 at 03:26 AM.
 
Old 12-17-2009, 11:10 AM   #4
deadeyes
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Registered: Aug 2006
Posts: 605

Original Poster
Rep: Reputation: 79
So I did some more research and I found out that in /etc/dhclient.conf (location depending on distro) you can add the following to have static addition of multiple domain-name (search mydomain mydomain2 in /etc/resolv.conf):
Code:
append domain-name "mydomain mydomain2"
BUT: this will always add those search domains to your /etc/resolv.conf.
Another way is by installing openresolv and adding the following line to /etc/resolvconf.conf
Code:
search_domains="mydomain mydomain2"
BUT: this will again always add those entries.

REAL SOLUTION:
I found something about dhclient-script (resides in /sbin). This is just a bash script so you can easily change this script to your needs.
I changed make_resolv_conf() and added a few lines in the beginning of the file to initialize some variables (which you have to tune to your network).
After the code is changed only the first 3 variables should be edited to match your network where you want to add those additional search domains.
Code:
# Definition of variables
INTERFACE="eth0"
OFFICE_NETWORK="192.168.50."
ADDITIONAL_DOMAINS="mydomain mydomain2"

make_resolv_conf() {
  if [ x$PEER_DNS = x ] || [ x$PEER_DNS = xyes ]; then
    if [ "x$new_domain_name" != x ] || [ "x$new_domain_name_servers" != x ]; then
      conf="# Generated by dhclient for interface $interface\n"
      if [ "x$new_domain_name" != x ]; then
        # DO NOT MOVE THESE: if put with the variables, the interface wont have an IP yet
        IP=$(ifconfig $INTERFACE | grep inet\ addr: | grep -o -E "[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}" | head -n1)
        ISATOFFICE=$(echo $IP | grep $OFFICE_NETWORK > /dev/null ; echo $?)
        if [ "$ISATOFFICE" = "0" ]; then
           conf="${conf}search $new_domain_name $ADDITIONAL_DOMAINS\n"
        else
           conf="${conf}search $new_domain_name\n"
        fi
      fi
      for nameserver in $new_domain_name_servers; do
        conf="${conf}nameserver $nameserver\n"
      done
      if [ -x /sbin/resolvconf ]; then
        printf "$conf" | resolvconf -a "$interface"
      else
        printf "$conf" > /etc/resolv.conf
        chmod 644 /etc/resolv.conf
      fi
    fi
  fi
  # If we're making confs, may as well make an ntp.conf too
  make_ntp_conf
}
For people who want to use this I will put a unified diff:
Code:
--- /sbin/dhclient-script.bak   2009-12-17 17:05:36.000000000 +0100
+++ /sbin/dhclient-script       2009-12-17 17:59:17.000000000 +0100
@@ -22,12 +22,24 @@
 # 4. TIMEOUT not tested. ping has a flag I don't know, and I'm suspicious
 # of the $1 in its args.

+# Definition of variables
+INTERFACE="eth0"
+OFFICE_NETWORK="192.168.50."
+ADDITIONAL_DOMAINS="mydomain mydomain2"
+
 make_resolv_conf() {
   if [ x$PEER_DNS = x ] || [ x$PEER_DNS = xyes ]; then
     if [ "x$new_domain_name" != x ] || [ "x$new_domain_name_servers" != x ]; then
       conf="# Generated by dhclient for interface $interface\n"
       if [ "x$new_domain_name" != x ]; then
-        conf="${conf}search $new_domain_name\n"
+       # DO NOT MOVE THESE: if put with the variables, the interface wont have an IP yet
+       IP=$(ifconfig $INTERFACE | grep inet\ addr: | grep -o -E "[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}" | head -n1)
+       ISATOFFICE=$(echo $IP | grep $OFFICE_NETWORK > /dev/null ; echo $?)
+       if [ "$ISATOFFICE" = "0" ]; then
+          conf="${conf}search $new_domain_name $ADDITIONAL_DOMAINS\n"
+       else
+           conf="${conf}search $new_domain_name\n"
+       fi
       fi
       for nameserver in $new_domain_name_servers; do
         conf="${conf}nameserver $nameserver\n"
As you can see: only a few lines of code!

I will do a final test when I am home in a few hours
 
Old 12-22-2009, 03:25 AM   #5
deadeyes
Member
 
Registered: Aug 2006
Posts: 605

Original Poster
Rep: Reputation: 79
Quote:
Originally Posted by deadeyes View Post
So I did some more research and I found out that in /etc/dhclient.conf (location depending on distro) you can add the following to have static addition of multiple domain-name (search mydomain mydomain2 in /etc/resolv.conf):
Code:
append domain-name "mydomain mydomain2"
BUT: this will always add those search domains to your /etc/resolv.conf.
Another way is by installing openresolv and adding the following line to /etc/resolvconf.conf
Code:
search_domains="mydomain mydomain2"
BUT: this will again always add those entries.

REAL SOLUTION:
I found something about dhclient-script (resides in /sbin). This is just a bash script so you can easily change this script to your needs.
I changed make_resolv_conf() and added a few lines in the beginning of the file to initialize some variables (which you have to tune to your network).
After the code is changed only the first 3 variables should be edited to match your network where you want to add those additional search domains.
Code:
# Definition of variables
INTERFACE="eth0"
OFFICE_NETWORK="192.168.50."
ADDITIONAL_DOMAINS="mydomain mydomain2"

make_resolv_conf() {
  if [ x$PEER_DNS = x ] || [ x$PEER_DNS = xyes ]; then
    if [ "x$new_domain_name" != x ] || [ "x$new_domain_name_servers" != x ]; then
      conf="# Generated by dhclient for interface $interface\n"
      if [ "x$new_domain_name" != x ]; then
        # DO NOT MOVE THESE: if put with the variables, the interface wont have an IP yet
        IP=$(ifconfig $INTERFACE | grep inet\ addr: | grep -o -E "[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}" | head -n1)
        ISATOFFICE=$(echo $IP | grep $OFFICE_NETWORK > /dev/null ; echo $?)
        if [ "$ISATOFFICE" = "0" ]; then
           conf="${conf}search $new_domain_name $ADDITIONAL_DOMAINS\n"
        else
           conf="${conf}search $new_domain_name\n"
        fi
      fi
      for nameserver in $new_domain_name_servers; do
        conf="${conf}nameserver $nameserver\n"
      done
      if [ -x /sbin/resolvconf ]; then
        printf "$conf" | resolvconf -a "$interface"
      else
        printf "$conf" > /etc/resolv.conf
        chmod 644 /etc/resolv.conf
      fi
    fi
  fi
  # If we're making confs, may as well make an ntp.conf too
  make_ntp_conf
}
For people who want to use this I will put a unified diff:
Code:
--- /sbin/dhclient-script.bak   2009-12-17 17:05:36.000000000 +0100
+++ /sbin/dhclient-script       2009-12-17 17:59:17.000000000 +0100
@@ -22,12 +22,24 @@
 # 4. TIMEOUT not tested. ping has a flag I don't know, and I'm suspicious
 # of the $1 in its args.

+# Definition of variables
+INTERFACE="eth0"
+OFFICE_NETWORK="192.168.50."
+ADDITIONAL_DOMAINS="mydomain mydomain2"
+
 make_resolv_conf() {
   if [ x$PEER_DNS = x ] || [ x$PEER_DNS = xyes ]; then
     if [ "x$new_domain_name" != x ] || [ "x$new_domain_name_servers" != x ]; then
       conf="# Generated by dhclient for interface $interface\n"
       if [ "x$new_domain_name" != x ]; then
-        conf="${conf}search $new_domain_name\n"
+       # DO NOT MOVE THESE: if put with the variables, the interface wont have an IP yet
+       IP=$(ifconfig $INTERFACE | grep inet\ addr: | grep -o -E "[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}" | head -n1)
+       ISATOFFICE=$(echo $IP | grep $OFFICE_NETWORK > /dev/null ; echo $?)
+       if [ "$ISATOFFICE" = "0" ]; then
+          conf="${conf}search $new_domain_name $ADDITIONAL_DOMAINS\n"
+       else
+           conf="${conf}search $new_domain_name\n"
+       fi
       fi
       for nameserver in $new_domain_name_servers; do
         conf="${conf}nameserver $nameserver\n"
As you can see: only a few lines of code!

I will do a final test when I am home in a few hours
It does work as wanted.
Only thing is that when you don't have any network connected, you will get the search line from the office.
But that has no influence as you don't have network
 
  


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