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Mock is a tool for building packages. It can build packages for different architectures and different Fedora or RHEL 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.


If you want to contribute to code, please checkout for more inforations.

Otherwise just run "yum install mock".


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

usermod -a -G mock [User name] && newgrp mock

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.

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
  • lvm_root - caching buildroots using LVM
  • mount - allows you to mount directories into chroot
  • package_state - dumps list of available and installed packages
  • pm_request - Executes package manager commands requested by processes runninng in the chroot.
  • root_cache - cache buildroots (as tar file).
  • 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 machine to chroot

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 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 on EL 6 and EL 7: Yum, and DNF

Starting with the Rawhide builds for Fedora 23, Mock requires DNF to run properly. Since not all parts of DNF are available on EL 6 and EL 7, Mock cannot be run there with the default configuration.

There are however two workarounds available:

  • For one time runs it is possible to pass --yum as an option on the command line.
  • To make yum the default package manager, a change in /etc/mock/site-defaults.cfg or inside of any /etc/mock/*.cfg file is necessary:

config_opts['package_manager'] = 'yum'

For more information, please see the blog entry by Miroslav Suchý.


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

Of course 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

See Also