Lennart Poettering
5c08da586f
When using systemd-repart as an installer that replicates the install
medium on another medium it is useful to reference the root
partition/usr partition or verity data that is currently booted, in
particular in A/B scenarios where we have two copies and want to
reference the one we currently use. Let's add a CopyBlocks=auto for this
case: for a partition that uses that we'll copy a suitable partition
from the host.
CopyBlocks=auto finds the partition to copy like this: based on the
configured partition type uuid we determine the usual mount point (i.e.
for the /usr partition type we determine /usr/, and so on). We then
figure out the block device behind that path, through dm-verity and
dm-crypt if necessary. Finally, we compare the partition type uuid of
the partition found that way with the one we are supposed to fill and
only use it if it matches (the latter is primarily important on
dm-verity setups where a volume is likely backed by two partitions and
we need to find the right one).
This is particularly fun to use in conjunction with --image= (where
we'll restrict the device search onto the specify device, for security
reasons), as this allows "duplicating" an image like this:
# systemd-repart --image=source.raw --empty=create --size=auto target.raw
If the right repart data is embedded into "source.raw" this will be able
to create and initialize a partition table on target.raw that carrries
all needed partitions, and will stream the source's file systems onto it
as configured.
System and Service Manager
Details
Most documentation is available on systemd's web site.
Assorted, older, general information about systemd can be found in the systemd Wiki.
Information about build requirements is provided in the README file.
Consult our NEWS file for information about what's new in the most recent systemd versions.
Please see the Hacking guide for information on how to hack on systemd and test your modifications.
Please see our Contribution Guidelines for more information about filing GitHub Issues and posting GitHub Pull Requests.
When preparing patches for systemd, please follow our Coding Style Guidelines.
If you are looking for support, please contact our mailing list or join our IRC channel.
Stable branches with backported patches are available in the stable repo.