77ae8d704f
* Replace "snap download" with tool that uses snap store's coherence feature
This is important for parallel image builds to ensure all pre-seeded snaps
have the same versions across image variants.
* Inject a proxy into the build providing a snapshot view of the package repo.
When the REPO_SNAPSHOT_STAMP variable is set, the auto/build script will attempt
to launch a transparent HTTP proxy on port 8080, and insert an iptables rule to
redirect all outgoing HTTP requests to this proxy.
The proxy, contained in the `magic-proxy` Python script, examines each request
and silently overrides those pointing to InRelease files or files that are
listed in InRelease files. It will instead provide the contents of the requested
file as it was at REPO_SNAPSHOT_STAMP, by downloading the corresponding asset
"by hash".
* Use series files with dependency handling to generate hook symlinks dynamically
This patch currently only applies to the "ubuntu-cpc" project.
More and more logic has been going into the hook scripts to decide
under which conditions they should run or not. As we are moving
to parallelized builds of image sets, this will get even more
complicated. Base hooks will have to know which image sets they
belong to and modification of the dependency chain between scripts
will become more complicated and prone to errors, as the number of
image sets grows.
This patch introduces explicit ordering and dependency handling for
scripts through the use of `series` files and an explicit syntax
for dependency specification.
TL;DR
In order to generate the hooks for a specific image target set, call the
make-hooks script, located in hooks.d as
./make-hooks --hooks-dir ../hooks <image_set>
where image_set is the name of a series file (e.g. "vagrant") without leading
path components. Do not check in the hooks folder, it is automatically
generated by auto/config during Live Build runs.
Hook placement and ordering
Scripts live in subfolders below the hooks.d folder. Currently the folders
chroot and base exist. The folder with the name extra is reserved for
private scripts, which are not included in the source of livecd-rootfs. The
scripts are not numbered, instead the order of their execution depends on the
order in which they are listed in a series file.
Series files are placed in subfolders hooks.d/base/series or
hooks.d/extra/series. Each series file contains a list of scripts to be
executed. Empty lines and lines starting with a # are ignored.
Series files in extra/series override files in base/series with the same
name. For example, if a series file base/series/cloudA exists and a series
file extra/series/cloudA, then the latter will be preferred.
A series file in extra/series may also list scripts that are located in the
chroot and base folders. In addition, series files can depend on other
series files. For example, the series files for most custom images look similar
to this:
depends disk-image
depends extra-settings
extra/cloudB.binary
Where disk-image and extra-settings may list scripts and dependencies which
are to be processed before the script extra/cloudB.binary is called.
ACHTUNG: live build runs scripts with the suffix ".chroot" in a batch separate from scripts ending in ".binary". Even if you arrange them interleaved in your series files, the chroot scripts will be run before the binary scripts.
Image set selection for Live Build
During a Live Build, enumerated symbolic links are generated based on the
contents of one or more series files. The series files are selected according
to the contents of the IMAGE_TARGETS environment variable. For example, in
order to trigger the build of squashfs and vagrant, list them in the
IMAGE_TARGETS variable as squashfs,vagrant. The separator can be a comma,
a semi-colon or whitespace.
The generation of the symbolic links is triggered from the auto/config script,
from where the contents of the IMAGE_TARGETS environment variable are passed
on to the make-hooks script.
Symlink generation
Since Live Build itself does not know about series files, a traditional hooks
folder is generated using the make-hooks script. The script takes as arguments
the names of the series files to be processed.
The script parses the series files and generates enumerated symbolic links for
all entries. Per default, these are placed into a directory named hooks next
to the hooks.d directory. This can be changed using the --hooks-dir
parameter.