This has been requested many times before. Let's add it finally.
GPT auto-discovery for /var is a bit more complex than for other
partition types: the other partitions can to some degree be shared
between multiple OS installations on the same disk (think: swap, /home,
/srv). However, /var is inherently something bound to an installation,
i.e. specific to its identity, or actually *is* its identity, and hence
something that cannot be shared.
To deal with this this new code is particularly careful when it comes to
/var: it will not mount things blindly, but insist that the UUID of the
partition matches a hashed version of the machine-id of the
installation, so that each installation has a very specific /var
associated with it, and would never use any other. (We actually use
HMAC-SHA256 on the GPT partition type for /var, keyed by the machine-id,
since machine-id is something we want to keep somewhat private).
Setting the right UUID for installations takes extra care. To make
things a bit simpler to set up, we avoid this safety check for nspawn
and RootImage= in unit files, under the assumption that such container
and service images unlikely will have multiple installations on them.
The check is hence only required when booting full machines, i.e. in
in systemd-gpt-auto-generator.
To help with putting together images for full machines, PR #14368
introduces a repartition tool that can automatically fill in correctly
calculated UUIDs on first boot if images have the var partition UUID
initialized to all zeroes. With that in place systems can be put
together in a way that on first boot the machine ID is determined and
the partition table automatically adjusted to have the /var partition
with the right UUID.
chase_symlinks() would return negative on error, and either a non-negative status
or a non-negative fd when CHASE_OPEN was given. This made the interface quite
complicated, because dependning on the flags used, we would get two different
"types" of return object. Coverity was always confused by this, and flagged
every use of chase_symlinks() without CHASE_OPEN as a resource leak (because it
would this that an fd is returned). This patch uses a saparate output parameter,
so there is no confusion.
(I think it is OK to have functions which return either an error or an fd. It's
only returning *either* an fd or a non-fd that is confusing.)
Some chattrs only work sensible if you set them right after opening a
file for create (think: FS_NOCOW_FL). Others only work when they are
applied when the file is fully written (think: FS_IMMUTABLE_FL). Let's
take that into account when copying files and applying a chattr to them.
Previously, when we'd copy an individual file we'd synthesize a
user.crtime_usec xattr with the source's creation time if we can
determine it. As the creation/birth time was until recently not
queriable form userspace this effectively just propagated the same xattr
on the source to the same xattr on the destination. However, current
kernels now allow to query the birthtime using statx() and we do make
use of that now. Which means that suddenly we started synthesizing these
xattrs much more regularly.
Doing this actually does make sense, but only in very few cases:
not for the typical regular files we copy, but certainly when dealing
with disk images. Hence, let's keep this kind of propagation, but let's
make it a flag and default to off. Then turn it on whenever we deal with
disk images, and leave it off otherwise.
This is particularly relevant as overlayfs combining a real fs, and a
tmpfs on top will result in EOPNOTSUPP when it is attempted to open a
file with xattrs for writing, as tmpfs does not support xattrs, and
hence the copy-up cannot work. Hence, let's avoid synthesizing this
needlessly, to increase compat with overlayfs.
Now that we don't (mis-)use the env file parser to parse kernel command
lines there's no need anymore to override the used newline character
set. Let's hence drop the argument and just "\n\r" always. This nicely
simplifies our code.
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
