4dbfab66a1
CentOS 7 is the only distro we support currently that doesn't have Python 3 installed in some form in the base images. For centos 7 add an early install of it in the yum element so we can have all the in-chroot scripts assume Python 3. There is only one package that causes issues; yaml which comes from EPEL. Everywhere else it is a base package, but we don't have a way to say "enable epel to install this". Just hack it in, we don't want to go reworking the world for CentOS 7 at this point. Also add python3 and it's yaml library to the centos 8 path. This brings in the "user" python3 in /urs/bin/python3 (the "system" python3 is already installed). Again, this just lets us assume /usr/bin/python3 in scripts for all platforms. package-installs is one of these things running python in the chroot, and unfortunately we have elements that use it at 01- level in pre-installd. Thus to make sure python3 is there nice and early, run it at 0 level, but make sure it comes after yum/dnf update. Change-Id: I088fc4284e889147ca9a375d4a159264cff53484
yum
Provide yum specific image building glue.
RHEL/Fedora/CentOS and other yum based distributions need specific yum customizations.
Customizations include caching of downloaded yum packages outside of the build chroot so that they can be reused by subsequent image builds. The cache increases image building speed when building multiple images, especially on slow connections. This is more effective than using an HTTP proxy as a yum cache since the same rpm from different mirrors is often requested.
Custom yum repository configurations can also be applied by defining DIB_YUM_REPO_CONF to a space separated list of repo configuration files. The files will be copied to /etc/yum.repos.d/ during the image build, and then removed at the end of the build. Each repo file should be named differently to avoid a filename collision.