distccd(1) General Commands Manual distccd(1)
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 "nobody".
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 sys-
tem, 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 --daemon
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 so.
For traditional Unix inetd, a line like this can be added to /etc/inetd.conf:
distcc stream tcp nowait.6000 root /usr/local/bin/distccd distccd --inetd
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 com-
--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. (Dae-
mon 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, all clients are allowed. Unauthorized connections are rejected by closing the TCP connection immediately. A
warning is logged on the server but nothing is sent ot the client.
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 rec-
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 inetd
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.
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
Specifies the maximum time to keep a cached pch file. The value is computed based on the last file access, and is constrained to be
at most 72 hours (the default).
Specifies the maximum total disk use in Mb allowed for the pch cache. A value of zero (the default) allows the cache to grow without
an explicit upper size limit.
Specifies the minimum disk free space in Mb to preserve on the filesystem containing the pch cache. The default is 2048, and the
minimum is 512. --priority PRIORITY Specifies an integer priority for the build machine. Machines with higher priorities will be
ordered towards the beginning of the DISTCC_HOSTS list by Xcode. This setting is not used by distcc.
distcc can pass either a relative or an absolute name for the compiler to distccd. If distcc is given an explicit absolute compiler file-
name, 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 mas-
querade 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.
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 skipped.
If set to 1, temporary files are not deleted after use.
Note that DISTCC_LOG does not affect the log destination for the server.
On Linux, turn on the TCP_DEFER_ACCEPT socket option. Defaults to on.
TMPDIR Directory for temporary files such as preprocessor output. By default /tmp/ is used.
The Mac OS X version of distccd includes support for precompiled header (pch) files. distccd caches these files in TMPDIR, and provides
options for managing the cache based on file access times and disk use. The pch files are downloaded from the client machines as needed
and stored on a per user, per client machine basis. To minimize build times the pch cache should be sufficiently large. If there is insuf-
ficient space then pch files may be repeatedly downloaded during a build. distccd will emit a warning if it detects that the cache con-
straints require discarding recently downloaded pch files (possibly due to a full disk.)
distcc(1), ccache(1), gcc(1), make(1) http://distcc.samba.org/
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, Dim-
itri Papadopoulos and others noted in the NEWS file. Please report bugs to <firstname.lastname@example.org>.
23 October 2003 distccd(1)