05bba4cbbd
Original fix proposed by Stanislav German-Evtushenko (giner) CPC Ubuntu cloud images default to enabling a serial console connection via the kernel commandline option `console=ttyS0`. Many clouds support the serial connection, and utilize it for debugging purposes. Virtualbox supports the serial connection as well. In Bionic and earlier images, Vagrant boxes created a serial log file in the directory of the Vagrantfile by default. However this is not standard behaviour for Vagrant images, and so it was removed in Eoan onwards. Starting in Eoan, there were reports of image booting slowdown (1874453 is a single example). After testing, it was determined that the serial connection starting, without a device attached, was the cause of the slow down. However, we did not want to revert to the old functionality of creating a file. Much thanks to <giner> for providing the Ruby syntax for sending to File::NULL. This option will not create a local file, however, the default Vagrantfile configuration is overwritable via a users Vagrantfile. The original syntax for creating a file local to the users Vagrantfile has been included as an example.
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.