If you use multiple machines or manage virtual machines, it is going to be difficult to map IP address and hostname in private network. DHCP server and DNS server will resolve it. But you might want to generate /etc/resolv.conf by DHCP server. This article will describe how to generate /etc/resolv.conf by DHCP server.
Table of Contents
1 The goal /etc/resolv.conf
The nameserver 192.168.11.2 manages hiroom2.com network. The nameserver 192.168.11.1 manages the internet.
search hiroom2.com nameserver 192.168.11.2 nameserver 192.168.11.1
2 Configuration of DHCP server
Define domain-name and domain-name-servers in /etc/dhcp/dhcpd.conf.
subnet 192.168.11.0 netmask 255.255.255.0 {
option domain-name "hiroom2.com";
option domain-name-servers 192.168.11.2, 192.168.11.1;
option routers 192.168.11.1;
}
The mapping between dhcpd.conf and resolv.conf is as below.
| dhcpd.conf | resolv.conf |
|---|---|
| option domain-name | serach |
| option domain-name-servers | nameserver |
3 Client Fedora/CentOS
When PEERDNS is defined in /etc/sysconfig/network-scripts/ifcfg-xxx, /etc/resolv.conf will be generated by DHCP server. Client Fedora/CentOS defines PEERDNS by default.
# cat /etc/sysconfig/network-scripts/ifcfg-eth0 TYPE="Ethernet" BOOTPROTO="dhcp" DEFROUTE="yes" PEERDNS="yes" PEERROUTES="yes" DEVICE="eth0" ONBOOT="yes" NAME="eth0"
4 Client Debian
/etc/resolv.conf is generated in client Debian by default.
$ sudo cat /etc/NetworkManager/NetworkManager.conf [main] plugins=ifupdown,keyfile [ifupdown] managed=false
5 Client Ubuntu
/etc/resolv.conf is not generated in client Ubuntu by default.
$ cat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by # resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE # OVERWRITTEN nameserver 127.0.1.1 search hiroom2.com
You need to disable dnsmasq in NetworkManager.
$ sudo diff -uprN /etc/NetworkManager/NetworkManager.conf{.org,}
--- /etc/NetworkManager/NetworkManager.conf.org 2016-04-28 01:07:32.015679999 +0900
+++ /etc/NetworkManager/NetworkManager.conf 2016-04-28 01:07:45.307679999 +0900
@@ -1,6 +1,6 @@
[main]
plugins=ifupdown,keyfile,ofono
-dns=dnsmasq
+#dns=dnsmasq
[ifupdown]
managed=false
$ sudo systemctl restart network-manager
/etc/resolv.conf is generated in client Ubuntu.
$ cat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by # resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE # OVERWRITTEN nameserver 192.168.11.2 nameserver 192.168.11.1 search hiroom2.com