Difference between revisions of "Udhcpc"

From Alpine Linux
Jump to: navigation, search
m
(Added options from interfaces file.)
Line 3: Line 3:
 
You may want to customize the behavior of the default DHCP client (udhcpc from busybox), which is called by /sbin/ifup by having "dhcp" in /etc/network/interfaces.
 
You may want to customize the behavior of the default DHCP client (udhcpc from busybox), which is called by /sbin/ifup by having "dhcp" in /etc/network/interfaces.
  
The default behavior is driven by the script /usr/share/udhcpc/default.script
+
The default behavior is driven by the script /usr/share/udhcpc/default.script
 +
 
 +
Entries in /etc/network/interfaces for dhcp interfaces will drive the udhcpc command line. For example: 
 +
'''
 +
auto eth0
 +
iface eth0 inet dhcp
 +
        hostname myhostname
 +
'''
 +
Will set these parameters on the command line: 
 +
-i eth0 -x hostname:myhostname 
 +
 
 +
The hostname will send the DHCP option to the server to tell the server the name of this client. 
 +
 
  
 
Its default configuration may be overwritten by /etc/udhcpc/udhcpc.conf
 
Its default configuration may be overwritten by /etc/udhcpc/udhcpc.conf

Revision as of 21:31, 2 January 2021

Tango-view-fullscreen.png
This material needs expanding ...

Please help us expand this article by contributing.

You may want to customize the behavior of the default DHCP client (udhcpc from busybox), which is called by /sbin/ifup by having "dhcp" in /etc/network/interfaces.

The default behavior is driven by the script /usr/share/udhcpc/default.script

Entries in /etc/network/interfaces for dhcp interfaces will drive the udhcpc command line. For example: auto eth0 iface eth0 inet dhcp

       hostname myhostname

Will set these parameters on the command line: -i eth0 -x hostname:myhostname

The hostname will send the DHCP option to the server to tell the server the name of this client.


Its default configuration may be overwritten by /etc/udhcpc/udhcpc.conf

Authorized key:value pairs are:

key default value possible values
NO_GATEWAY - <list of iface names>
IF_METRIC - <metric value>
IF_PEER_DNS yes <anything but yes>
RESOLV_CONF /etc/resolv.conf no ; NO ; -
NO_DNS - <list of iface names>

Example /etc/udhcpc/udhcpc.conf:

RESOLV_CONF="no" # Prevents overwriting of /etc/resolv.conf

Custom scripts can be added as /etc/udhcpc/pre-* and /etc/udhcpc/post-* to be run before/after deconfig/renew/bound DHCP events - they must be marked as executable by root, e.g. chmod 744

As an example, /etc/udhcpc/post-bound/mtu could contain, to change the interface MTU from the default (1500) to 1492, which is useful if on ADSL (which uses 8 bytes):

r=$(/sbin/ip route | grep ^default | head -n 1)
# Needs iproute2 package, rather than busybox's "ip", to change mtu
/sbin/ip route replace $r mtu 1492