6. Invoking dhcp-client

dhcp-client runs on a per interface basis. By default the client will start up, look for the first ethernet interface which is down, and attempt to use it to perform DHCP operations through. You can force the client to use a specific interface by referring it to a particular interface. See section Command Line Options.

6.1 Command Line Options

• -h Print out usage.

• -v Print out version information

• -a

  Always run in the foreground and do not go into the background.

• -c

  Clear the cache. This is useful in case a stale cache is left behind by an earlier invocation.

• -k

  Kill a dhcp-client instance. Coupled with the -i option this will kill a specific instance of dhcp-client. Otherwise the first dhcp-client found on an active ethernet interface is terminated.

• -p

  Forces dhcp-client to use promiscious mode. This is only useful on systems which are sufficiently broken that require promiscious mode to receive broadcast messages.

• -w

  Wake a dhcp-client instance. Coupled with the -i option this will wake up a client on a specified interface and cause it to either rebind, or renew earlier depending on which timer is next. Use this to force the client to reacquire a lease.

• -s

  Print out status information on the most recent lease acquired by the client.

• -i interface

  Force dhcp-client to use the interface specified. This is useful to make sure dhcp-client uses a specific interface if the host is multi-homed.

• -l level

  Generate messages at the level specified. The level should be an integer between 0 - 4. The levels are no messages, error messages, info messages (default), warnings, diagnostic-messages, respectively. Each level includes all messages below it. The default is info messages which also include error messages.

• -m mac address

  Fake a mac address during the DHCP operation. This will only affect the DHCP operations and no others. This is useful for debugging a DHCP server that is not behaving itself.