====== Metamode ======

===== Introduction =====

Metamode is an incremental build system for %%FreeBSD%%, which uses bmake's //meta mode// and filemon(4) to create metadata files, substantially decreasing build times by only building what has changed since the last build.

Note: Enabling ''%%META_MODE%%'' also implies (enables) ''%%NO_CLEAN%%'' in the buildworld process

===== Setup =====

  - Add ''%%WITH_META_MODE=YES%%'' to ''%%/etc/src-env.conf%%''
  - Run ''%%# kldload filemon%%''
  - Run ''%%# make cleanworld%%'' once. If objects don't have ''%%.meta%%'' files then ''%%META_MODE%%'' won't do the right thing on an incremental build. (([[https://lists.freebsd.org/pipermail/freebsd-current/2016-May/061552.html|[CFT  WITH_META_MODE: Working incremental build]]))
  - [[https://docs.freebsd.org/en/books/handbook/cutting-edge/#makeworld|FreeBSD buildworld]] will now create meta files to improve the performance of future builds.

===== Caveats =====

  * <del>Don't mix ''%%WITH_META_MODE%%'' with ''%%ccache(1)%%'' as mentioned in [[https://forums.freebsd.org/threads/61548/#post-354470|this thread]]</del> .
    * For all versions from 12.0-RELEASE and going forward, both technologies work as expected.
  * ''%%WITH_META_MODE%%'' is not the same thing as ''%%WITH_DIRDEPS_BUILD%%'', which is an alternative, experimental build system.
    * [[http://www.crufty.net/sjg/docs/freebsd-meta-mode.htm|Building FreeBSD in meta mode]]
    * [[https://www.bsdcan.org/2016/schedule/attachments/354_Improving_the_FreeBSD_build_bdrewery_2016.pdf|Improving the FreeBSD Build (BSDCan 2016)]]
    * [[http://www.crufty.net/help/sjg/bmake-meta-mode.htm|Description of meta mode in bmake(1)]]
    * [[https://github.com/xmj/xmj.github.io/blob/master/articles/sysadmin/builds_ccache_memcached.md#dirdeps|Speeding up builds on FreeBSD]]

===== References =====

  * ''%%src.conf(5)%%''
  * ''%%build(7)%%''

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{{tag>HowTo}}