path: root/man/distccd.1

.TH distccd 1 "2 June 2008"
.SH "NAME"
distccd \- distributed C/C++ compiler server
.SH "SYNOPSIS"
.B distccd --daemon 
.I [OPTIONS]
.SH "DESCRIPTION"
.I distccd 
is the server for the distcc(1) distributed compiler.  It accepts and
runs compilation jobs for network clients.
.PP
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.  
.PP
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.
.PP
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 
.B --listen
and 
.B --allow
options can be used for simple IP-based access control.
.PP
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 
.B --user
option, or the user called "distcc", or the user called "nobody".
.PP
distccd does not have a configuration file; it's behaviour is
controlled only by command-line options and requests from
clients.
.SH "STANDALONE SERVER"
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.
.PP
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
.RS
.PP
# service distcc start
.RE
.PP
To start distccd as a standalone service, run a command like
this either as root or an ordinary user:
.RS
.PP
# distccd --daemon
.RE
.SH "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.
.PP
distccd should be started just as for a standalone server,
except that the 
.B --no-detach
option should be used so that the super-server can monitor it.
.PP
For example, to add distccd as a process to Linux
sysvinit, add this line to 
.I /etc/inittab
.RS
.PP
dscc:2345:respawn:/usr/local/bin/distccd --verbose --no-detach --daemon
.RE
.SH "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.
.PP
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.
.PP
For traditional Unix inetd, a line like this can be added
to /etc/inetd.conf:
.RS
.PP
distcc stream tcp nowait.6000 root /usr/local/bin/distccd distccd --inetd
.RE
.PP
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.
.SH "TERMINATING DISTCCD"
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 
.I --pid-file
option to record its process ID.  Shutting down the server in this way
should allow any jobs currently in progress to complete.
.SH "OPTIONS"
.TP
.B --help
Display summary usage information.
.TP
.B --version
Shows the daemon version and exits.
.TP
.B -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.)
.TP 
.B -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.
.TP
.B -p, --port PORT
Set the TCP port to listen on, rather than the default of 3632.
(Daemon mode only.)
.TP
.B --listen ADDRESS
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.)
.TP
.B -P, --pid-file FILE
Save daemon process id to file FILE.  (Daemon mode only.)
.TP
.B --user USER
If distccd gets executed as root, change to user USER.
.TP
.B -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.
.TP
.B --job-lifetime SECONDS
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.
.TP
.B --no-detach
Do not detach from the shell that started the daemon.  
.TP
.B --no-fork
Don't fork children for each connection, to allow attaching gdb.
Don't use this if you don't understand it!
.TP
.B --log-file FILE
Send messages to file FILE instead of syslog.
Logging directly to a file is significantly faster than
going via syslog and is recommended.
.TP
.B --log-level LEVEL
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
.I critical, error, warning, notice, info, 
or
.I debug.
.TP
.B --log-stderr
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 mode.
.TP
.B --verbose
Include debug messages in log.  Equivalent to
.B --log-level=debug
.TP
.B --wizard
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.
.TP
.B --stats
Turn on the statistics HTTP server. By default it is off.
(Daemon mode only.)
.TP
.B --stats-port PORT
Set the TCP port to listen on for HTTP requests, rather than the default of 3633.
(Daemon mode only.)
.TP
.B --inetd
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.
.TP 
.B --daemon
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.
.TP 
.B --zeroconf
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.
.B This option is only available if distccd was compiled with
.B Avahi support enabled.
.SH "SEARCH PATHS"
.PP
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.
.PP
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
.B DISTCCD_PATH
environment variable may be used to set the path.
.PP
The search path is logged when --verbose is given.  In case of
confusion, check the logs.
.PP
When distccd is run over ssh, the 
.I $HOME/.ssh/environment 
file may be useful in setting the path.  See 
.B ssh(1).
.SH "DIAGNOSTICS"
distccd logs messages to syslog's 
.I daemon
facility by
default, which normally writes to 
.I /var/log/daemon 
or
.I /var/log/messages.  
Log messages can be sent to a
different file using the 
.B --log-file option.
.SH "ENVIRONMENT VARIABLES"
.TP
.B "DISTCC_CMDLIST"
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.
.TP
.B "DISTCC_CMDLIST_NUMWORDS"
The number of words, from the end of the command, to match. The default is 1. 
.TP
.B "DISTCCD_PATH"
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.
.TP
.B "DISTCC_SAVE_TEMPS"
If set to 1, temporary files are not deleted after use.
.PP
Note that 
.B "DISTCC_LOG"
does not affect the log destination for the server.
.TP
.B "DISTCC_TCP_DEFER_ACCEPT"
On Linux, turn on the TCP_DEFER_ACCEPT socket option.  Defaults to on.
.TP
.B "TMPDIR"
Directory for temporary files such as preprocessor output.  By default
/tmp/ is used.
.SH "SEE ALSO"
\fBdistcc\fR(1), \fBpump\fR(1), \fBinclude_server\fR(1), \fBgcc\fR(1),
\fBmake\fR(1), and  \fBccache\fR(1)
.I http://code.google.com/p/distcc/
.SH "BUGS"
IP-based access control is not secure against attackers able to spoof
TCP connections, and cannot discriminate different users on a client.
.PP 
TCP connections are not secure against attackers able to observe or
modify network traffic.
.PP
Because ccache does not cache compilation from 
.B .i
files, it is not useful to call it from distccd.
.SH "LICENCE"
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.
.SH "AUTHOR"
distcc was written by Martin Pool <mbp@sourcefrog.net>, with the
co-operation of many scholars including Wayne Davison, Frerich Raabe,
Dimitri Papadopoulos and others noted in the NEWS file. 
See \fBpump\fR(1) for the authors of pump mode.
Please report bugs to <distcc@lists.samba.org>.