Build Server

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  • Base chroot environment for the creation of most binary packages which will be copied to the Binary Package Server.
  • Packages, which don't need to be built, for example Oracle's Java SE Development Kit (JDK), can be fetched from the Mirror Server.
  • Software stacks built upon specialized binary packages, require their own chroot environment. If possible, avoid this.
  • For reproducibility, Portage and Profiles are frozen with the help of version control system (git in our case). This is only done on the Mirror Server.
  • When building packages in a chroot environment, the portage and overlay versions need to set.

Portage Snapshotting

To be able to reliably rebuild packages, we are working with a snapshotted/versioned portage tree.

Updating the snapshot to latest

We are using emerge-webrsync since it features an already determined version, checksum- and gpg-validation.

user $ git clone "${PORTAGE_GIT_REPO}" portage
user $
cd portage
user $
PORTAGE_RSYNC_EXTRA_OPTS="--exclude=/.git --exclude=/.gitignore" PORTDIR="${PWD}" emerge-webrsync
Fetching most recent snapshot ...
Trying to retrieve 20140821 snapshot from ...
Fetching file portage-20140821.tar.xz.md5sum ...
Fetching file portage-20140821.tar.xz.gpgsig ...
Fetching file portage-20140821.tar.xz ...
Checking digest ...
Getting snapshot timestamp ...
Syncing local tree ...

If you get the following instead then there is no newer snapshot available
user $ PORTAGE_RSYNC_EXTRA_OPTS="--exclude=/.git --exclude=/.gitignore" PORTDIR="${PWD}" emerge-webrsync
Fetching most recent snapshot ...
 * Latest snapshot date: 20140821
 * Approximate snapshot timestamp: 1408668300
 *        Current local timestamp: 1408667701
 * The current local timestamp is possibly identical to the
 * timestamp of the latest snapshot. In order to force sync, use
 * the --revert option or remove the timestamp file located at
 * '/run/user/1000/portage/metadata/timestamp.x'.

Set the tag and push if there was an update:

user $ cd portage/
user $
git add -A
user $
snapshot_date=$(date --date=@$(( $(cut -f 1 -d " " metadata/timestamp.x) - 86400 )) +%Y-%m-%d)
user $
git commit -m "Update portage tree to ${snapshot_date}"
user $
git tag -a -m "Tagging ${snapshot_date}" ${snapshot_date}
user $
git push && git push --tags
user $
echo "snapshot date: ${snapshot_date}"

The subtraction of 86400 (1 day in seconds) above is to account for the fact that the snapshot for a given day is taken at 00:45 UTC on the following day and the timestamp contained in the tarball therefore is one day ahead (see /usr/bin/emerge-webrsync).

The meaning of the tag is therefore: contains at least all changes from that day (and possibly a bit more).

Chroot Setup


At least the following is required beforehand to ensure reproducible building:

  • a versioned portage tree
  • versioned overlays (if any)


  • Create a staging root directory and extract a stage3 or stage4 tarball
  • Mount proc, sys and dev (required for portage to control the tty, determine available storage space, etc.)
  • Copy /etc/resolv.conf
  • Checkout the versioned portage tree (since you probably won't have git yet in the tree)
  • Enter the chroot
root # stagingRoot=/var/staging/staging-base
root #
mkdir -p "${stagingRoot}"
root #
tar -xjpf /var/tmp/your-stage4.tbz2 -C "${stagingRoot}"
root #
mount -t proc none "${stagingRoot}/proc"
root #
mount --rbind /dev/ "${stagingRoot}/dev/"
root #
mount --rbind /sys/ "${stagingRoot}/sys/"
root #
cp -af /etc/resolv.conf "${stagingRoot}/etc/"
root #
git clone "${PORTAGE_GIT_REPO}" "${stagingRoot}/usr/portage"
root #
chmod -R a+rX "${stagingRoot}/usr/portage"
root #
chroot "${stagingRoot}" /usr/bin/env -i HOME="/root" TERM="${TERM}" /bin/bash --login
We are deliberately using a special command for entering the chroot to avoid leaking environment variables

  • If needed, put the mirror for fetch restricted ebuilds in a local mirror definition:

  • Add the following to generate binary packages during installation:

FEATURES="${FEATURES} buildpkg cgroup ipc-sandbox network-sandbox parallel-fetch"
  • Make sure that the repository configuration points to your git mirror as well:

main-repo = gentoo
location = /usr/portage
sync-type = git
sync-uri =
  • Rebuild everything:
root # emerge -e world