DHCPCD-RUN-HOOKS(8) System Manager's Manual DHCPCD-RUN-HOOKS(8)

dhcpcd-run-hooks — DHCP client configuration script

dhcpcd-run-hooks is used by dhcpcd(8) to run any system and user defined hook scripts. System hook scripts are found in /usr/lib/dhcpcd/dhcpcd-hooks and the user defined hooks are /etc/dhcpcd.enter-hook. and /etc/dhcpcd.exit-hook. The default install supplies hook scripts for configuring /etc/resolv.conf and the hostname. Your distribution may have included other hook scripts to say configure ntp or ypbind. A test hook is also supplied that simply echos the dhcp variables to the console from DISCOVER message.

The hooks scripts are loaded into the current shell rather than executed in their own process. This allows each hook script, such as /etc/dhcpcd.enter-hook to customise environment variables or provide alternative functions to hooks further down the chain. As such, using the shell builtins exit, exec or similar will cause dhcpcd-run-hooks to exit at that point.

Each time dhcpcd-run-hooks is invoked, $interface is set to the interface that dhcpcd is run on and $reason is set to the reason why dhcpcd-run-hooks was invoked. DHCP information to be configured is held in variables starting with the word new_ and old DHCP information to be removed is held in variables starting with the word old_. dhcpcd can display the full list of variables it knows about by using the -V, --variables argument.

Here's a list of reasons why dhcpcd-run-hooks could be invoked:

dhcpcd is starting up and any pre-initialisation required should be performed now.
dhcpcd has detected the carrier is up. This is generally just a notification and no action need be taken.
dhcpcd lost the carrier. The cable may have been unplugged or association to the wireless point lost.
dhcpcd lost the carrier but the interface configuration is persisted. The OS has to support wireless roaming or IP Persistence for this to happen.
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dhcpcd informed a DHCP server about its address and obtained other configuration details.
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dhcpcd obtained a new lease from a DHCP server.
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dhcpcd renewed its lease.
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dhcpcd has rebound to a new DHCP server.
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dhcpcd successfully requested a lease from a DHCP server.
dhcpcd assigned a delegated prefix to the interface.
dhcpcd obtained an IPV4LL address, or one was removed.
dhcpcd has been configured with a static configuration which has not been obtained from a DHCP server.
dhcpcd is monitoring the interface for a 3rd party to give it an IP address.
dhcpcd failed to contact any DHCP servers but was able to use an old lease.
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dhcpcd's lease or state expired and it failed to obtain a new one.
dhcpcd received a NAK from the DHCP server. This should be treated as EXPIRE.
dhcpcd has been instructed to reconfigure an interface.
dhcpcd has received an IPv6 Router Advertisement, or one has expired.
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dhcpcd stopped running on the interface.
dhcpcd has stopped entirely.
The interface has been removed.
dhcpcd failed to operate on the interface. This normally happens when dhcpcd does not support the raw interface, which means it cannot work as a DHCP or ZeroConf client. Static configuration and DHCP INFORM is still allowed.
dhcpcd received an OFFER from a DHCP server but will not configure the interface. This is primarily used to test the variables are filled correctly for the script to process them.

dhcpcd will clear the environment variables aside from $PATH. The following variables will then be set, along with any protocol supplied ones.

the name of the interface.
the protocol that triggered the event.
as described above.
the pid of dhcpcd.
the link status of $interface: unknown, up or down.
preference, lower is better.
$interface is wireless, otherwise 0.
flags.
MTU.
the SSID the interface is connected to.
A list of interfaces, in order of preference.
if the interface is up, otherwise false. This is more than IFF_UP and may not be equal.
if the interface is down, otherwise false. This is more than IFF_UP and may not be equal.
Address family waiting for, as defined in dhcpcd.conf(5).
the name of the profile selected from dhcpcd.conf(5).
space-separated list of delegated prefixes.

When dhcpcd-run-hooks runs, it loads /etc/dhcpcd.enter-hook, any scripts found in /usr/lib/dhcpcd/dhcpcd-hooks in lexical order, then finally /etc/dhcpcd.exit-hook.

dhcpcd(8)

Roy Marples <roy@marples.name>

Please report them to https://roy.marples.name/projects/dhcpcd

dhcpcd will validate the content of each option against its encoding. For string, ascii, raw or binhex encoding it's up to the user to validate it for the intended purpose.

When used in a shell script, each variable must be quoted correctly.

August 31, 2022 Debian