distccd - distributed C/C++ compiler server
distccd --daemon [OPTIONS]
distccd is the server for the distcc(1) distributed compiler. It
accepts and runs compilation jobs for network clients.
distcc can run over either TCP or a connection command such as ssh(1).
TCP connections are fast but relatively insecure. SSH connections are
secure but slower.
For SSH connections, distccd must be installed on the volunteer but
should not run as a daemon -- it will be started over SSH as needed.
SSH connections have several advantages: neither the client nor server
listens on any new ports; compilations run with the privileges of the
user that requested them; unauthorized users cannot access the server;
and source and output is protected in transit.
For TCP connections, distccd can run either from an inetd-style
program, or as a standalone server. Standalone mode is recommended
because it is slightly more efficient and allows distccd to regulate
the number of incoming jobs. The --listen and --allow options can be
used for simple IP-based access control.
distcc may be started either by root or any other user. If run by
root, it gives away privileges and changes to the user specified by the
--user option, or the user called "distcc", or the user called
distccd does not have a configuration file; it’s behaviour is
controlled only by command-line options and requests from clients.
The recommended method for running distccd is as a standalone server.
distccd will listen for network connections and fork several child
processes to serve them.
If you installed distcc using a packaged version you may be able to
start the server using the standard mechanism for your operating
system, such as
# service distcc start
To start distccd as a standalone service, run a command like this
either as root or an ordinary user:
# distccd --daemon
RUNNING FROM INIT
distccd may be run as a standalone daemon under the control of another
program like init(8) or daemontools. The super-server starts distccd
when the system boots, and whenever it exits.
distccd should be started just as for a standalone server, except that
the --no-detach option should be used so that the super-server can
For example, to add distccd as a process to Linux sysvinit, add this
line to /etc/inittab
dscc:2345:respawn:/usr/local/bin/distccd --verbose --no-detach
RUNNING FROM INETD
distccd may be started from a network super-server such as inetd or
xinetd. In this case inetd listens for network connections and invokes
distccd when one arrives.
This is slightly less efficient than running a standalone distccd
daemon. distccd is not able to regulate the number of concurrent jobs
accepted, but there may be an option in your inetd configuration to do
For traditional Unix inetd, a line like this can be added to
distcc stream tcp nowait.6000 root /usr/local/bin/distccd
inetd imposes a limit on the rate of connections to a service to
protect against accidental or intentional overuse. The default in
Linux NetKit inetd is 40 per minute, which is far too low for distccd.
The .6000 option raises the limit to 6000 per minute.
To shut down a standalone server, send a SIGTERM signal to the parent
process. The most reliable way to do this from a script is to use the
--pid-file option to record its process ID. Shutting down the server
in this way should allow any jobs currently in progress to complete.
--help Display summary usage information.
Shows the daemon version and exits.
-j, --jobs JOBS
Sets a limit on the number of jobs that can be accepted at any
time. By default this is set to two greater than the number of
CPUs on the machine, to allow for some processes being blocked
on network IO. (Daemon mode only.)
-N, --nice NICENESS
Makes the daemon more nice about giving up the CPU to other
tasks on the machine. NICENESS is an increment to the current
priority of the process. The range of priorities depends on the
operating system but is typically 0 to 20. By default the
niceness is increased by 5.
-p, --port PORT
Set the TCP port to listen on, rather than the default of 3632.
(Daemon mode only.)
Instructs the distccd daemon to listen on the IP address
ADDRESS. This can be useful for access control on dual-homed
hosts. (Daemon mode only.)
-P, --pid-file FILE
Save daemon process id to file FILE. (Daemon mode only.)
If distccd gets executed as root, change to user USER.
-a, --allow IPADDR[/MASK]
Instructs distccd to accept connections from the IP address
IPADDR. A CIDR mask length can be supplied optionally after a
trailing slash, e.g. 192.168.0.0/24, in which case addresses
that match in the most significant MASK bits will be allowed.
If no --allow options are specified, distccd will exit
immediately! Unauthorized connections are rejected by closing
the TCP connection immediately. A warning is logged on the
server but nothing is sent to the client.
Kills a distccd job if it runs for more than SECONDS seconds.
This prevents denial of service from clients that don’t properly
disconnect and compilers that fail to terminate. By default this
is turned off.
Do not detach from the shell that started the daemon.
Don’t fork children for each connection, to allow attaching gdb.
Don’t use this if you don’t understand it!
Send messages to file FILE instead of syslog. Logging directly
to a file is significantly faster than going via syslog and is
Set the minimum severity of error that will be included in the
log file. Useful if you only want to see error messages rather
than an entry for each connection. LEVEL can be any of the
standard syslog levels, and in particular critical, error,
warning, notice, info, or debug.
Send log messages to stderr, rather than to a file or syslog.
This is mainly intended for use in debugging. Do not use in
Include debug messages in log. Equivalent to --log-level=debug
Turn on all options appropriate for starting distccd under gdb:
run as a daemon, log verbosely to stderr, and do not detach or
fork. For wizards only.
Turn on the statistics HTTP server. By default it is off.
(Daemon mode only.)
Set the TCP port to listen on for HTTP requests, rather than the
default of 3633. (Daemon mode only.)
Serve a client connected to stdin/stdout. As the name suggests,
this option should be used when distccd is run from within a
super-server like inetd. distccd assumes inetd mode when stdin
is a socket.
Bind and listen on a socket, rather than running from inetd.
This is used for standalone mode. distccd assumes daemon mode
at startup if stdin is a tty, so --daemon should be explicitly
specified when starting distccd from a script or in a non-
interactive ssh connection.
Register the availability of this distccd server using Avahi
Zeroconf DNS Service Discovery (DNS-SD). This allows distcc
clients on the local network to access this distccd server
without explicitly listing its host name or IP address in their
distcc host list: the distcc clients can just use "+zeroconf" in
their distcc host lists. This option is only available if
distccd was compiled with Avahi support enabled.
distcc can pass either a relative or an absolute name for the compiler
to distccd. If distcc is given an explicit absolute compiler filename,
that name is used verbatim on both the client and server. If the
compiler name is not an absolute path, or if the client is used in
masquerade mode, then the server’s PATH is searched.
distccd inherits its search path from its parent process. By default
distccd tries to remove directories that seem to contain distccd
masquerade links, to guard against inadvertent recursion. The
DISTCCD_PATH environment variable may be used to set the path.
The search path is logged when --verbose is given. In case of
confusion, check the logs.
When distccd is run over ssh, the $HOME/.ssh/environment file may be
useful in setting the path. See ssh(1).
distccd logs messages to syslog’s daemon facility by default, which
normally writes to /var/log/daemon or /var/log/messages. Log messages
can be sent to a different file using the --log-file option.
If the environment variable DISTCC_CMDLIST is set, load a list
of supported commands from the file named by DISTCC_CMDLIST, and
refuse to serve any command whose last DISTCC_CMDLIST_MATCHWORDS
last words do not match those of a command in that list. See
the comments in src/serve.c.
The number of words, from the end of the command, to match. The
default is 1.
When starting distccd, if this value is set it will be used
unaltered for the command-execution PATH. The code that
normally tries to remove masquerade directories from the path is
If set to 1, temporary files are not deleted after use.
Note that DISTCC_LOG does not affect the log destination for the
On Linux, turn on the TCP_DEFER_ACCEPT socket option. Defaults
TMPDIR Directory for temporary files such as preprocessor output. By
default /tmp/ is used.
distcc(1), pump(1), include_server(1), gcc(1), make(1), and ccache(1)
IP-based access control is not secure against attackers able to spoof
TCP connections, and cannot discriminate different users on a client.
TCP connections are not secure against attackers able to observe or
modify network traffic.
Because ccache does not cache compilation from .i files, it is not
useful to call it from distccd.
You are free to use distcc. distcc (including this manual) may be
copied, modified or distributed only under the terms of the GNU General
Public Licence version 2 or later. distcc comes with absolutely no
warrany. A copy of the GPL is included in the file COPYING.
distcc was written by Martin Pool <email@example.com>, with the co-
operation of many scholars including Wayne Davison, Frerich Raabe,
Dimitri Papadopoulos and others noted in the NEWS file. See pump(1)
for the authors of pump mode. Please report bugs to
9 June 2008 distccd(1)