---
name: "ahcpd"
section: "8"
platform: "linux"
package: "ahcpd"
version: "0.53-3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/ahcpd"
---

# ahcpd(8)

ad-hoc configuration daemon

## NAME

ahcpd - ad-hoc configuration daemon

## SYNOPSIS

**ahcpd** *option*... \[ **--** \] *interface*...

## DESCRIPTION

AHCP is a configuration protocol that can replace DHCP on networks without transitive connectivity, such as mesh networks.

## OPTIONS

- **-m** *multicast-address*

  Specify the link-local multicast address to be used by AHCP.  The default is ff02::cca6:c0f9:e182:5359.

- **-p** *port*

  Specify the UDP port number to be used by AHCP.  The default is 5359.

- **-n**

  Operate as a forwarder: participate in the flooding protocol, but don't actually perform any configuration.

- **-4**

  Only attempt to configure IPv4 addresses.

- **-6**

  Only attempt to configure IPv6 addresses.

- **-N**

  Do not configure DNS.

- **-t** *time*

  Specify the time, in seconds, for which leases are requested.  The default is slightly over one hour.  Must be between five minutes and a year.

- **-s** *script*

  Specify the configuration script to run.  The default is **/etc/ahcp/ahcp-config.sh**.

- **-d** *level*

  Set the debug level to *level* (default 1).

- **-i** *filename*

  Specify the filename containing this host's unique id.  The default is **/var/lib/ahcp-unique-id**. If it doesn't exist, it will be created by **ahcpd**.

- **-c** *filename*

  Specify the name of the configuration file.

- **-C** *statement*

  Specify a configuration statement directly on the command line.

- **-D**

  Daemonise at startup.

- **-L** *logfile*

  Specify a file to log random \`\`how do you do?'' messages to.  This defaults to standard error if not daemonising, and to **/var/log/ahcpd.log** otherwise.

- **-I** *pidfile*

  Specify a file to write our process id to.  The default is **/var/run/ahcpd.pid.**

## CONFIGURATION FILE FORMAT

The configuration is a sequence of lines, each of which starts with one of the keywords below.  Blank lines are ignored.  Comments are introduced with an octothorp \`\`**#**'' and terminate at the end of the line.

The following keywords are recognised:

- **mode** **server**\|**client**\|**forwarder**

  Specifies whether the daemon operates as a server, a client, or a forwarder.  If omitted, the default is to operate as a client, unless the **-n** flag is present on the command line.  If present, this must be the first line in the configuration file.

- **prefix** *prefix*

  Specifies a prefix to use for configuring clients.  This keyword is only valid in server configurations, and may be specified twice, once for IPv4 and once for IPv6.

- **lease-dir** *directory*

  Specifies a directory to store lease files.  This keyword is only valid in server configurations.

- **name-server** *address*

  Specifies the address of a DNS server to configure clients with.  This keyword is only valid in server configurations, and may be repeated multiple times.

- **ntp-server** *address*

  Specifies the address of an NTP server to configure clients with.  This keyword is only valid in server configurations, and may be repeated multiple times.

## FILES

- **/var/lib/ahcp-unique-id**

  An 8-byte long file containing this host's unique id.  If it doesn't exist, a new unique id will be generated from an interface's MAC address.

- **/etc/ahcp/ahcp-config.sh**

  The script that performs the actual configuration.  It will be passed one argument, which is either **start** or **stop**.

- **/etc/ahcp/ahcp-local.sh**

  If this is an executable script, it will be called by **ahcp-config.sh** just after configuring or deconfiguring. It will be passed one argument, which is either **start** or **stop**.

## SIGNALS

- **SIGUSR1**

  Print **ahcpd**'s status to standard output or to the log file.

- **SIGUSR2**

  Check all interfaces for status changes, then reopen the log file.

## NOTES

Since the AHCP protocol is designed for mesh networks, it doesn't have any provisions for setting routing parameters such as a default gateway, the IPv4 network mask and the IPv6 list of on-link prefixes; these are expected to be provided by a full-fledged routing protocol for mesh nodes, and by router advertisements for ordinary nodes.

The AHCP server should use NTP to synchronise its clock.  If a server instance of **ahcpd** doesn't detect time synchronisation, it will only give out leases for a short period of time, and be extremely conservative about releasing them. Note that an SNTP client is not enough — **ahcpd** actually checks with the kernel for time synchronisation, so real NTP is necessary.

## SEE ALSO

[**dhcpcd**(8)](/dhcpcd/8.md), [**dhclient**(8)](/dhclient/8.md), [**babeld**(8)](/babeld/8.md), [**olsrd**(8)](/olsrd/8.md), [**ntpd**(8)](/ntpd/8.md), *The Ad-Hoc Configuration Protocol*.

## AUTHOR

Juliusz Chroboczek.