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diff --git a/documentation/dev-manual/disk-space.rst b/documentation/dev-manual/disk-space.rst new file mode 100644 index 0000000000..efca82601d --- /dev/null +++ b/documentation/dev-manual/disk-space.rst @@ -0,0 +1,61 @@ +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK + +Conserving Disk Space +********************* + +Conserving Disk Space During Builds +=================================== + +To help conserve disk space during builds, you can add the following +statement to your project's ``local.conf`` configuration file found in +the :term:`Build Directory`:: + + INHERIT += "rm_work" + +Adding this statement deletes the work directory used for +building a recipe once the recipe is built. For more information on +"rm_work", see the :ref:`ref-classes-rm-work` class in the +Yocto Project Reference Manual. + +When you inherit this class and build a ``core-image-sato`` image for a +``qemux86-64`` machine from an Ubuntu 22.04 x86-64 system, you end up with a +final disk usage of 22 Gbytes instead of &MIN_DISK_SPACE; Gbytes. However, +&MIN_DISK_SPACE_RM_WORK; Gbytes of initial free disk space are still needed to +create temporary files before they can be deleted. + +Purging Obsolete Shared State Cache Files +========================================= + +After multiple build iterations, the Shared State (sstate) cache can contain +multiple cache files for a given package, consuming a substantial amount of +disk space. However, only the most recent ones are likely to be reused. + +The following command is a quick way to purge all the cache files which +haven't been used for a least a specified number of days:: + + find build/sstate-cache -type f -mtime +$DAYS -delete + +The above command relies on the fact that BitBake touches the sstate cache +files as it accesses them, when it has write access to the cache. + +You could use ``-atime`` instead of ``-mtime`` if the partition isn't mounted +with the ``noatime`` option for a read only cache. + +For more advanced needs, OpenEmbedded-Core also offers a more elaborate +command. It has the ability to purge all but the newest cache files on each +architecture, and also to remove files that it considers unreachable by +exploring a set of build configurations. However, this command +requires a full build environment to be available and doesn't work well +covering multiple releases. It won't work either on limited environments +such as BSD based NAS:: + + sstate-cache-management.py --remove-duplicated --cache-dir=sstate-cache + +This command will ask you to confirm the deletions it identifies. +Run ``sstate-cache-management.sh`` for more details about this script. + +.. note:: + + As this command is much more cautious and selective, removing only cache files, + it will execute much slower than the simple ``find`` command described above. + Therefore, it may not be your best option to trim huge cache directories. |