Distcc is a program to distribute builds of C, C++, Objective C or Objective C++ code across several machines on a network. It should always generate the same results as a local build, is simple to install and use, and is usually much faster than a local compile. The cool part is one can use it together with native Arch build tools such as makepkg.
- 1 Terms
- 2 Getting started
- 3 Configuration
- 4 Compile
- 5 Monitoring progress
- 6 "Cross Compiling" with distcc
- 7 Troubleshooting
- The master is the computer which initiates the compilation.
- The slave(s) accept compilation requests send by the master.
For other distros, or even OSes including Windows through using Cygwin, refer to the distcc docs.
The configuration for the slaves is stored in
/etc/conf.d/distccd. The available command line options are listed in the distcc manual. At a minimum, configure the allowed address ranges in CIDR format:
A nice tool for converting address ranges to CIDR format can be found here: CIDR Utility Tool.
For use with makepkg
/etc/makepkg.conf in the following three sections:
- BUILDENV has distcc unbanged i.e. without exclamation point.
- Uncomment the DISTCC_HOSTS line and add the IP addresses of the slaves then a slash and the number of threads they are to use. The subsequent IP address/threads should be separated by a white space. This list is ordered from most powerful to least powerful (processing power).
- Adjust the MAKEFLAGS variable to correspond to the number of sum of the number of individual values specified for the max threads per server. In the example below, this is 5+3+3=11. If users specify more than this sum, the extra theoretical thread(s) will be blocked by distcc and appear as such in monitoring utils such as distccmon-text described below.
Example using relevant lines:
BUILDENV=(distcc fakeroot color !ccache check !sign) MAKEFLAGS="-j11" DISTCC_HOSTS="192.168.0.2/5 192.168.0.3/3 192.168.0.4/3"
If users wish to use distcc through SSH, add an "@" symbol in front of the IP address in this section. If key-based auth is not setup on the systems, set the DISTCC_SSH variable to ignore checking for authenticated hosts, i.e. DISTCC_SSH="ssh -i"
For use without makepkg
The minimal configuration for distcc on the master includes the setting of the available slaves. This can either be done by setting the addresses in the environment variable
DISTCC_HOSTS or in either of the configuration files
Example for setting the slave address using
$ export DISTCC_HOSTS="192.168.0.3,lzo,cpp 192.168.0.4,lzo,cpp"
Example for setting the slave addresses in the hosts configuration file:
Instead of explicitly listing the server addresses one can also use the avahi zeroconf mode. To use this mode
+zeroconf must be in place instead of the server addresses and the distcc daemons on the slaves have to be started using the
--zeroconf option. Note that this option does not support the pump mode!
The examples add the following options to the address:
lzo: Enables LZO compression for this TCP or SSH host (slave).
cpp: Enables distcc-pump mode for this host (slave). Note: the build command must be wrapped in the pump script in order to start the include server.
A description for the pump mode can be found here: HOW DISTCC-PUMP MODE WORKS and distcc's pump mode: A New Design for Distributed C/C++ Compilation
To use distcc-pump mode for a slave, users must start the compilation using the pump script otherwise the compilation will fail.
Compile via makepkg as normal.
To compile a source file using the distcc pump mode, use the following command:
$ pump distcc g++ -c hello_world.cpp
In this case the pump script will execute distcc which in turn calls g++ with "-c hello_world.cpp" as parameter.
To compile a Makefile project, first find out which variables are set by the compiler. For example in gzip-1.6, one can find the following line in the Makefile:
CC = gcc -std=gnu99. Normally the variables are called
CC for C projects and
CXX for C++ projects. To compile the project using distcc it would look like this:
$ wget ftp://ftp.gnu.org/pub/gnu/gzip/gzip-1.6.tar.xz $ tar xf gzip-1.6.tar.xz $ cd gzip-1.6 $ ./configure $ pump make -j2 CC="distcc gcc -std=gnu99"
This example would compile gzip using distcc's pump mode with two compile threads. For the correct
-j setting have a look at What -j level to use?
Progress can be monitored via several methods.
- tailing log file
Invoke distccmon-text to check on compilation status:
$ distccmon-text 29291 Preprocess probe_64.c 192.168.0.2 30954 Compile apic_noop.c 192.168.0.2 30932 Preprocess kfifo.c 192.168.0.2 30919 Compile blk-core.c 192.168.0.2 30969 Compile i915_gem_debug.c 192.168.0.2 30444 Compile block_dev.c 192.168.0.3 30904 Compile compat.c 192.168.0.3 30891 Compile hugetlb.c 192.168.0.3 30458 Compile catalog.c 192.168.0.4 30496 Compile ulpqueue.c 192.168.0.4 30506 Compile alloc.c 192.168.0.4
One can have this program run continuously by using watch or by appending a space followed by integer to the command which corresponds to the number of sec to wait for a repeat query:
$ watch distccmon-text
$ distccmon-text 2
One can also simply tail
/var/log/messages.log on daemon:
# tail -f /var/log/messages.log
"Cross Compiling" with distcc
There are currently two methods from which to select to have the ability of distcc distribution of tasks over a cluster building i686 packages from a native x86_64 environment. Neither is ideal, but to date, there are the only two methods documented on the wiki.
An ideal setup is one that uses the unmodified ARCH packages for distccd running only once one each node regardless of building from the native environment or from within a chroot AND one that works with makepkg. Again, this Utopian setup is not currently known.
A discussion thread has been started on the topic; feel free to contribute.
Chroot method (preferred)
Assuming the user has a 32-bit chroot setup and configured on each node of the distcc cluster, the strategy is to have two separate instances of distccd running on different ports on each node -- one runs in the native x86_64 environment and the other in the x86 chroot on a modified port. Start makepkg via a schroot command invoking makepkg.
Add port numbers to DISTCC_HOSTS on the i686 chroot
Append the port number defined eariler (3692) to each of the hosts in
/opt/arch32/etc/makepkg.conf as follows:
DISTCC_HOSTS="192.168.1.101/5:3692 192.168.1.102/5:3692 192.168.1.103/3:3692"
Invoke makepkg from the Native Environment
$ schroot -p -- makepkg -src
Multilib GCC method (not recommended)
When building on an Arch ARM device, the developers highly recommend using the official project toolchains.
Extract the toolchain corresponding to the requisite architecture somewhere on the slave filesystem and edit
/etc/conf.d/distccd adjusting the PATH to allow the toolchain to be used.
Example with the toolchair extracted to
To read in the configuration file, restart
Optionally link it to your user's homedir if planning to build without makepkg. Example:
$ ln -s /mnt/data/x-tools8 x-tools8
- EmbToolkit: Tool for creating cross compilation tool chain; supports ARM and MIPS architectures; supports building of an LLVM based tool chain
- crosstool-ng: Similar to EmbToolkit; supports more architectures (see website for more information)
- Linaro: Provides tool chains for ARM development
EmbToolkit provides a nice graphical configuration menu (
make xconfig) for configuring the tool chain.
journalctl to find out what was going wrong:
$ journalctl $(which distccd) -e --since "5 min ago"
Make sure that the tool chain works for the user account under which the distcc daemon process gets started (default is nobody). The following will test if the tool chain works for user nobody. In
/etc/passwd change the login for the nobody user to the following:
$ cat /etc/passwd
... nobody:x:99:99:nobody:/:/bin/bash ...
Then cd into the directory containing the cross compiler binaries and try to execute the compiler:
# su nobody $ ./gcc --version bash: ./gcc: Permission denied
Users experiencing this error should make sure that groups permissions as described in #Other architectures are correctly in setup.
Make sure to change back
/etc/passwd to its original state after these modifications.
Alternatively, use sudo without changing the shell in /etc/passwd.
# sudo -u nobody gcc --version
Adjust log level
By default, distcc will log to
/var/log/messages.log as it goes along. One trick (actually recommended in the distccd manpage) is to log to an alternative file directly. Again, one can locate this in RAM via /tmp. Another trick is to lower to log level of minimum severity of error that will be included in the log file. Useful if only wanting 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.
Either call distcc with the arguments mentioned here on the master or appended it to DISTCC_ARGS in
/etc/conf.d/distccd on the slaves:
DISTCC_ARGS="--allow 192.168.0.0/24 --log-level error --log-file /tmp/distccd.log"
Failure work with CMake or other tools
CMake sometimes pass "response file" to gcc, but the distcc cannot deal with it. There is a patch file, but it has not been applied to upstream code. Users encountering this problem, can source this file or use the AUR[broken link: archived in aur-mirror] package.
Limit HDD/SSD usage
By default, distcc creates
$HOME/.distcc which stores transient relevant info as it serves up work for nodes to compile. Create a directory named .distcc in RAM such as /tmp and soft link to it in $HOME. This will avoid needless HDD read/writes and is particularly important for SSDs.
$ mv $HOME/.distcc /tmp $ ln -s /tmp/.distcc $HOME/.distcc
Use systemd to re-create this directory on a reboot (the soft link will remain until it is manually removed like any other file):
Create the following tmpfile.
d /tmp/.distcc 0755 <username> users -