dracut is not really ready to be installed with a non-/ prefix, and it
has a lot of hard-coded assumptions that it is going to run on the host
for which it is goign to generate an initramfs; for example, it
hard-codes calls to /lib/dracut/some-file in some of its modules. It
also uses the host system layout to decide whether it needs a
merged-usr or not.
Furthermore, dracut populates the temporary directory which content will
be used to generate the cpio, with a bunch of files, even before calling
any of the dracut modules.
The name for that temporary directory is not predictable (looks like the
output of 'mktemp -d dracut.XXXXXX', with names like dracut.1Vfn9F seen
while debugging).
As a consequence, we can't prepare the temporary directory with the
proper symlinks beforehand.
So, we provide a very-early module of our own, that will (hopefully) run
before any other module, to fixup the messed-up layout prepared by
dracut. This module moves the content of /lib, /bin, and /sbin, out and
into their counterparts in /usr, and creates the usual symlinks.
When we do not require a merged-usr, then we have nothing to do, so the
module checks for /lib being a symlink, as the hint that we want a
merged-usr or not.
Note: currently, we've seen nothing that dracut installed in /bin or
/sbin, but for trying to be future-proof, we also handle them; this
causes a spurious warning:
mv: cannot stat '..../build/buildroot-fs/cpio/tmp/dracut.YQnzNP/initramfs/bin/*': No such file or directory
Since there are already quite a bunch of similar failures in the
official modules bundled in dracut, an extra such issue or two should
not be too scary...
Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/3282261241https://gitlab.com/buildroot.org/buildroot/-/jobs/3282261239https://gitlab.com/buildroot.org/buildroot/-/jobs/3282261236
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Thierry Bultel <thierry.bultel@linatsea.fr>
Cc: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Dracut is the tool used by desktop distributions to build initrds.
In the embedded world, it can be very useful, too, for instance when
wanting to create an initramfs for a system recovery mode.
Whereas it is definitively possible to achieve this with buildroot, the
process is to have a dedicated buildroot configuration for that, and
perform a full build. Instead of doing that, dracut can pick the needed
binaries/shared libraries, configuration files, or kernel modules from
the 'target' directory.
The advantage is to save build time, and also to have a consistency
between the packages versions taken for the recovery and the production
filesystem.
The principle of dracut is based on the so-called 'dracut modules'. The
modules determine what will be included in the initramfs. For example,
one of dracut's modules checks the kernel modules that are included and
also includes the corresponding firmware blobs.
On the host, they are on host/lib/dracut/modules.d
Each directory as a prefix number for the order of execution, and
at least a "module-setup.sh" script.
Dracut sources all of them, and typically calls the "check()" function,
which is the placeholder for required binaries (that are aimed to be
polulated in the initrd), then the "depends()" function, that lists
other modules to depend on, and the "install()" function, that makes
the actual work.
Dracut was initially thought to work with systems using systemd,
but it can also work without it. Do to so, every "systemd-xxx"
module must be disabled in the dracut configuration file. For
convenience, the 05busybox-init module is provided, to support
busybox init system. Note that this module should *not* be enabled when
using systemd init. It is therefore only installed if busybox init is
selected.
Musl and uClibc make assumptions about the existence of some symlinks
that are not discoverable with readelf. Therefore, another module
05libc-links is provided that creates those links. The module is
installed regardless of which libc is used - the script itself discovers
if the links need to be installed based on which libc is found.
Signed-off-by: Thierry Bultel <thierry.bultel@linatsea.fr>
[arnout@mind.be: many changes]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Adam Duskett <aduskett@gmail.com>
[yann.morin.1998@free.fr: some additional fixups]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
