Let's make sure we use loop devices if we have access to them and
only fall back to regular files if we can't use loop devices. We
prefer loop devices because when using mkfs --root options, we have
to populate a temporary staging tree which means we're copying every
file twice instead of once when using loop devices.
The --empty option applies to the partition table of the block
device, not the number of definition files we've read. Also, even
if we don't find any definition files, let's not shortcut execution
so we can run repart on a device/loopback file to get information
on the partition table.
--include-partitions and --exclude-partitions now fully exclude
partitions from repart. Whenever a partition type is excluded, we
don't take any partitions of that type into account at all when
running systemd-repart.
--skip-partitions= is introduced to do what --exclude-partitions did
previously. Any skipped partitions are taken into acount when doing
size calculations, but are not yet populated.
Why do we need both concepts? Exclusion is needed so that we can
use shared repart definitions to generate bootable and non-bootable
images. When generating a non-bootable image, we use --exclude-partitions
to exclude the ESP partition. Skipping is needed so that we can
populate the root partition while skipping the ESP partition, get
the roothash of the root partition, use that to generate a UKI, and
finally populate the ESP partition with the UKI included.
It's only used to avoid BLKDISCARD on individual partitions at the moment.
It can take a lot of time to run on very slow devices, so avoid it for
them too.
Instead of having fopen_temporary() create the file either next
to an existing file or in tmp/, let's split this up clearly into
two different functions, one for creating temporary files next to
existing files, and one for creating a temporary file in a directory.
When repart is not operating on a block device, if we avoid using
any loop devices at all, it becomes possible to run repart without
needing root privileges.
Note that this also depends on the filesystems in use to support
population without needing root privileges (specifically, squashfs,
ext4 or btrfs).
By forking off a user namespace before running mkfs and ID mapping
the user running repart to root in the user namespace, we can make
sure that files in the generated filesystems are all owned by root
instead of the user running repart.
To make this work we have to make sure that all the files in the
root directory that's passed to the mkfs binary are owned by the
user running repart, so we have to drop the shortcut for only a
single root directory in partition_populate_directory().
Offline encryption can be done without mounting the luks device. For
now we still use loop devices to split out the partition we want to
write to but in a later commit we'll replace this with a regular file.
For offline encryption, we need to keep 2x the luks header size space
free at the end of the partition, so this means our encrypted partitions
will be 16M larger than before.
Let's allow filtering the partitions to operate on by partition
type UUID. This is necessary when building bootable images with a
verity protected root/usr partition as we can only build the UKI
image when we have the verity roothash which means we cannot populate
the EFI partition yet when we run repart initially to determine the
verity roothash.
If we skip some partition types in a first run of systemd-repart,
we don't want their partition numbers to be different than usual,
so let's change the allocation of partition numbers to account for
that.
Instead of exposing just the partition type UUID, let's expose the
GptPartitionType struct, which has a lot more information available
in a much more accessible way.
Also, let's get rid of SECONDARY/OTHER in PartitionDesignator. These
were only there to support preferred architectures in dissect-image.c,
but we can easily handle that by comparing architectures when we decide
whether to override a partition. This is done in a new function
compare_arch().
Instead of requiring users to guess the required space for partitions
populated with CopyFiles=, let's make an educated guess ourselves. We
can populate the filesystem once in a very large sparse file and see
how much data is actually used as a good indicator of the required size.
Daan De Meyer
Lennart Poettering
Luca Boccassi
Li kunyu