Miroslav Suchý edited this page Aug 13, 2018 · 63 revisions


Mock is a tool for building packages. It can build packages for different architectures and different Fedora, RHEL, and Mageia versions than the build host has. Mock creates chroots and builds packages in them. Its only task is to reliably populate a chroot and attempt to build a package in that chroot.

Mock also offers a multi-package tool, mockchain, that can build chains of packages that depend on each other.

Mock is capable of building SRPMs from source configuration management if the mock-scm package is present, then building the SRPM into RPMs. See --scm-enable in the documentation.


Mock is currently being used for all Fedora builds. It is called by Koji and Copr to build chroots and packages.

Release Notes

Tar balls

Tar balls can be found at: https://github.com/rpm-software-management/mock/releases


If you want to contribute to the code, please checkout https://github.com/rpm-software-management/mock for more information.

Otherwise just run

dnf install mock


All users that are to use mock must be added to the mock group.

usermod -a -G mock [User name]

:warning: Mock runs some parts of its code with root privileges. There are known ways to get root access once a user is in the mock group (and once he is able to run mock). This is possible when a user abuses the mock configuration options. Please do not add anyone who is not trustworthy to the mock group!

:notebook: To have this change take effect you have to either log out and log back in or run command newgrp -

Configuration files are in /etc/mock. Mock versions 0.8.0 and higher cache the downloaded rpm packages (via the yum_cache plugin), which speeds up subsequent builds by a considerable margin. Nevertheless, you may wish to change the default configuration to point to local repositories to speed up builds (see note below).

By default, builds are done in /var/lib/mock, so be sure you have room. Starting with mock 0.8.0 and higher, you can change this via the basedir config option.


  • bind_mount - bind mountpoints inside the chroot
  • ccache - compiler cache plugin
  • chroot_scan - allows you to retrieve build artifacts from buildroot (e.g. additional logs, coredumps)
  • compress_logs - compress logs
  • hw_info - prints HW information of builder
  • lvm_root - caching buildroots using LVM
  • mount - allows you to mount directories into chroot
  • overlayfs - plugin implementing snapshot functionality (similary to lvm_root)
  • package_state - dumps list of available and installed packages
  • pm_request - executes package manager commands requested by processes running in the chroot
  • root_cache - cache buildroots (as tar file)
  • scm - SCM integration module - builds directly from Git or Svn
  • selinux - on SELinux enabled box, this plugin will pretend, that SELinux is disabled in build environment
  • sign - call command on the produced rpm
  • tmpfs - mount buildroot directory as tmpfs
  • yum_cache - mount /var/cache/yum of your host machine to chroot

Plugins can be enabled on command line e.g --enable-plugin=chroot_scan. And you can set plugin options using e.g. '--plugin-option=root_cache:age_check=False'

Every plugin has a corresponding wiki page with docs.

Order of plugins hooks.


  • bootstrap - bootstrapping chroot. I.e., when building F28 on RHEL7, then first install very minimal bootstrap chroot with DNF and rpm from F28 and then use F28's rpm to install final F28 chroot.
  • forcearch - build for foreign architecture using emulated virtualization.
  • nosync - speed up build by making fsync(2) no-op.
  • modularity - support for Fedora Modularity.

Using Mock outside your git sandbox

Create your SRPM using rpmbuild -bs. Then change to the directory where your SRPM was created.

Now you can start mock with

mock -r <configname> --rebuild package-1.2-3.src.rpm

where <configname> is the name of a configuration file from /etc/mock/, without the /etc/mock path prefix and without the .cfg suffix.

Note that you can track the progress of mock using the logs stored in /var/lib/mock/<configfile>/result

Mock inside Docker

Since version 1.3.2 you can run mock inside of Docker. However you need to add SYS_ADMIN to docker container. I.e. run:

docker run --cap-add=SYS_ADMIN ...

:warning: Please note, that Mock inside of Docker skips unsharing of namespace, so it run in the same namespace as other program in the same container. You should not run any other application inside of that container. Mock print warning about this. You can suppress this warning, when you put in config

config_opts['docker_unshare_warning'] = False


See separate page: FAQ

Exit codes

Mock have various exist codes to signalize problem in build. See https://github.com/rpm-software-management/mock/blob/master/mock/py/mockbuild/exception.py#L26


List of known issues

If you encounter a bug running mock, please file it in Bugzilla, product "Fedora", component mock (Open Bugs).

If your problem is specific to EPEL, then file it against the "Fedora EPEL" product instead (Open Bugs).

Generate custom config file

Mock main config file is /etc/mock/site-defaults.cfg, which contains all defaults setting and all possible variables you can change. Then you have /etc/mock/<buildroot>.cfg for various buildroots, which contains settings for yum/dnf which are for various distribution different.

When you want to alter the config you may copy one and edit it manually, however if koji is already using such an config, then you can use mock-config --help for information how to generate one. E.g.: koji mock-config --tag f21-build --arch=aarch64 f21

You should not alter site-defaults.cfg unless you want to change settings for all users. You should put your changes to ~/.mock/user.cfg or to ~/.config/mock.cfg.

The order of reading and evaluating configuration files is:

  1. /etc/mock/site-defaults.cfg
  2. /etc/mock/<buildroot>.cfg
  3. ~/.mock/user.cfg
  4. ~/.config/mock.cfg (since mock-1.2.15)

Using file:// URLs in configs

Since version 1.4.1 you cannot use file:// in baseurl in Mock config's. If you want to use your local repo, you have to make it available inside of chroot using bind_mount plugin.

See Also

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