distcc.1

distcc编译器的源代码.好像是readhat公司开发的.

.TH distcc 1 "28 July 2004"
.SH "NAME"
distcc \- distributed C/C++/ObjC compiler
.SH "SYNOPSIS"
.B distcc 
.I <compiler> [COMPILER OPTIONS] 
.PP
.B distcc
.I [COMPILER OPTIONS]
.PP
.B <compiler>
.I [COMPILER OPTIONS]
.SH "DESCRIPTION"
.P 
distcc distributes compilation of C code across several machines on a
network.  distcc should always generate the same results as a local
compile, is simple to install and use, and is often much faster than a
local compile.
.PP
distcc sends the complete preprocessed source code and compiler
arguments across the network for each job, so the machines do not need
to share a filesystem, have the same headers or libraries installed,
or have synchronized clocks.
.PP
Compilation is driven by a "client" machine, which is typically the
developer's workstation or laptop.  The distcc client runs on this
machine, as does make, the preprocessor, the linker, and other stages
of the build process.  Any number of "volunteer" machines help the
client to build the program, by running the 
.B distccd(1) 
daemon, C compiler and assembler
as required.
.PP
distcc can run across either TCP sockets (on port 3632 by default), or
through a tunnel command such as ssh(1).  For TCP connections the
volunteers must run the distccd(1) daemon either directly or from inetd.
For SSH connections distccd must be installed but should
.B not
be listening for connections.  
.PP
TCP connections should only be used on secure networks because there
is no user authentication or protection of source or object code.  SSH
connections are typically 25% slower because of processor overhead for
encryption, although this can vary greatly depending on CPUs, network
and the program being built.
.PP
distcc is intended to be used with GNU Make's
.B -j 
option, which runs several compiler processes concurrently.  distcc
spreads the jobs across both local and remote CPUs.  Because distcc is
able to distribute most of the work across the network a higher
concurrency level can be used than for local builds.  The
.B -j 
value should normally be set to about twice the total number of
available CPUs, to allow for some tasks being blocked waiting for disk
or network IO.  distcc can also work with other build control tools
such as SCons.
.PP
It is strongly recommended that you install the same compiler version
on all machines participating in a build.  Incompatible compilers may
cause mysterious compile or link failures.
.SH "QUICKSTART"
.TP
1
For each machine, download distcc, unpack, and install.
.TP
2
On each of the servers, run 
.B distccd --daemon
optionally with 
.B --allow
options to restrict access.
.TP 
3
Put the names of the servers in your environment:
.RS
$ export DISTCC_HOSTS='localhost red green blue'
.RE
.TP
4
Build!
.RS
$ make -j8 CC=distcc
.RE
.SH "HOW IT WORKS"
distcc only ever runs the compiler and assembler remotely.
The preprocessor must always run locally because it needs to
access various header files on the local machine which may
not be present, or may not be the same, on the volunteer.
The linker similarly needs to examine libraries and object
files, and so must run locally.
.PP
The compiler and assembler take only a single input file (the
preprocessed source) and produce a single output (the object file).
distcc ships these two files across the network and can therefore run
the compiler/assembler remotely.
.PP
Fortunately, for most programs running the preprocessor is
relatively cheap, and the linker is called relatively
infrequent, so most of the work can be distributed.
.PP
distcc examines its command line to determine which of these
phases are being invoked, and whether the job can be
distributed.
.SH "OPTION SUMMARY"
Most options passed to distcc are interpreted as compiler options.
Two options are understood by distcc itself:
.TP 
.B --help
Displays summary instructions.
.TP
.B --version
Displays the distcc client version.
.SH "INSTALLING DISTCC"
There are three different ways to call distcc, to suit different
circumstances:
.RS
.PP
distcc can be installed under the name of the real compiler, to
intercept calls to it and run them remotely.  This "masqueraded"
compiler has the widest compatibility with existing source trees, and
is convenient when you want to use distcc for all compilation.  The
fact that distcc is being used is transparent to the makefiles.
.PP
distcc can be prepended to compiler command lines, such as "distcc cc
-c hello.c" or CC="distcc gcc".  This is convenient when you want to
use distcc for only some compilations or to try it out, but can cause
trouble with some makefiles or versions of libtool that assume $CC
does not contain a space.
.PP
Finally, distcc can be used directly as a compiler.  "cc" is always
used as the name of the real compiler in this "implicit" mode.  This
can be convenient for interactive use when "explicit" mode does not
work but is not really recommended for new use.
.RE
.PP
Remember that you should not use two methods for calling distcc at the
same time.  If you are using a masquerade directory, don't change CC and/or
CXX, just put the dirirectory early on your PATH.  If you're not using
a masquerade directory, you'll need to either change CC and/or CXX, or
modify the makefile(s) to call distcc explicitly.
.SH "MASQUERADING"
The basic idea is to create a "masquerade directory" which contains
links from the name of the real compiler to the distcc binary.  This
directory is inserted early on the PATH, so that calls to the compiler
are intercepted and distcc is run instead.  distcc then removes itself
from the PATH to find the real compiler.
.PP
For example:
.PP
.RS
.nf
# mkdir /usr/lib/distcc/bin
# cd /usr/lib/distcc/bin
# ln -s ../../../bin/distcc gcc
# ln -s ../../../bin/distcc cc
# ln -s ../../../bin/distcc g++
# ln -s ../../../bin/distcc c++
.fi
.RE
.PP
Then, to use distcc, a user just needs to put the directory
/usr/lib/distcc/bin early in the PATH, and have set a host list in
DISTCC_HOSTS or a file.  distcc will handle the rest.  
.PP
Note that this masquerade directory must occur on the PATH earlier
than the directory that contains the actual compilers of the same
names, and that any auxiliary programs that these compilers call (such
as as or ld) must also be found on the PATH in a directory after the
masquerade directory since distcc calls out to the real compiler with
a PATH value that has all directory up to and including the masquerade
directory trimmed off.
.PP
It is possible to get a "recursion error" in masquerade mode, which
means that distcc is somehow finding itself again, not the real
compiler.  This can indicate that you have two masquerade directories
on the PATH, possibly because of having two distcc installations in
different locations.  It can also indicate that you're trying to mix
"masqueraded" and "explicit" operation.
.SH "USING DISTCC WITH CCACHE"
ccache is a program that speeds software builds by caching the results
of compilations.  ccache is normally called before distcc, so that
results are retrieved from a normal cache.  Some experimentation may
be required for idiosyncratic makefiles to make everything work together.
.PP
The most reliable method is to set
.IP
.B CCACHE_PREFIX="distcc"
.PP
This tells ccache to run distcc as a wrapper around the real
compiler.  ccache still uses the real compiler to detect compiler
upgrades.
.PP
ccache  can then be run using either a masquerade directory 
.I or 
by
setting
.IP
.B CC="ccache gcc"
.PP
As of version 2.2, ccache does not cache compilation from preprocessed
source and so will never get a cache hit if it is run from distccd or
distcc.  It must be run only on the client side and before distcc to
be any use.
.SH "HOST SPECIFICATIONS"
A "host list" tells distcc which machines to use for compilation.  In
order, distcc looks in the 
.B $DISTCC_HOSTS
environment variable, the user's 
.B $DISTCC_DIR/hosts
file, and the system-wide host 
file.  If no host list can be found, distcc emits a warning and
compiles locally.
.PP
The host list is a simple whitespace separated list of host
specifications.  The simplest and most common form is a host names,
such as
.PP
.RS
.B localhost red green blue
.RE
.PP
distcc prefers hosts towards the start of the list, so machines should
be listed in descending order of speed.  In particular, when only a
single compilation can be run (such as from a configure script), the
first machine listed is used.  
.PP
Placing 
.I localhost
at the right point in the list is important to getting good
performance.  Because overhead for running jobs locally is low,
localhost should normally be first.  However, it is important that the
client have enough cycles free to run the local jobs and the distcc
client.  If the client is slower than the volunteers, or if there are
many volunteers, then the client should be put later in the list or
not at all.  As a general rule, if the aggregate CPU speed of the
client is less than one fifth of the total, then the client should be
left out of the list.
.PP
Performance depends on the details of the source and makefiles used
for the project, and the machine and network speeds.  Experimenting
with different settings for the host list and -j factor may improve
performance.
.PP
The syntax is
.PP
.nf
  DISTCC_HOSTS = HOSTSPEC ...
  HOSTSPEC = LOCAL_HOST | SSH_HOST | TCP_HOST | OLDSTYLE_TCP_HOST
  LOCAL_HOST = localhost[/LIMIT]
  SSH_HOST = [USER]@HOSTID[/LIMIT][:COMMAND][OPTIONS]
  TCP_HOST = HOSTID[:PORT][/LIMIT][OPTIONS]
  OLDSTYLE_TCP_HOST = HOSTID[/LIMIT][:PORT][OPTIONS]
  HOSTID = HOSTNAME | IPV4
  OPTIONS = ,OPTION[OPTIONS]
  OPTION = lzo
.fi
.PP
Here are some individual examples of the syntax:
.TP
.B localhost
The literal word "localhost" is interpreted specially to cause
compilations to be directly executed, rather than passed to a daemon
on the local machine.  If you do want to connect to a daemon on the
local machine for testing, then give the machine's IP address or real
hostname.  (This will be slower.)
.TP
.B IPV4
A literal IPv4 address, such as 
.B 10.0.0.1
.TP
.B HOSTNAME
A hostname to be looked up using the resolver.
.TP
.B :PORT
Connect to a specified decimal port number, rather than the default of
3632.
.TP
.B @HOSTID
Connect to the host over SSH, rather than TCP.  Options for the SSH
connection can be set in 
.B ~/.ssh/config
.TP
.B USER@
Connect to the host over SSH as a specified username.
.TP
.B :COMMAND 
Connect over SSH, and use a specified path to find the distccd