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(RHEL-17394) fstab-generator: Chase symlinks where possible #150

Merged
merged 7 commits into from
Feb 7, 2024
Merged

(RHEL-17394) fstab-generator: Chase symlinks where possible #150

merged 7 commits into from
Feb 7, 2024

Commits on Nov 27, 2023

  1. fstab-generator: Chase symlinks where possible (#6293) 

    This has a long history; see see 5261ba9
which originally introduced the behavior.  Unfortunately that commit
doesn't include any rationale, but IIRC the basic issue is that
systemd wants to model the real mount state as units, and symlinks
make canonicalization much more difficult.

At the same time, on a RHEL6 system (upstart), one can make e.g. `/home` a
symlink, and things work as well as they always did; but one doesn't have
access to the sophistication of mount units (dependencies, introspection, etc.)
Supporting symlinks here will hence make it easier for people to do upgrades to
RHEL7 and beyond.

The `/home` as symlink case also appears prominently for OSTree; see
https://ostree.readthedocs.io/en/latest/manual/adapting-existing/

Further work has landed in the nspawn case for this; see e.g.
d944dc9

A basic limitation with doing this in the fstab generator (and that I hit while
doing some testing) is that we obviously can't chase symlinks into mounts,
since the generator runs early before mounts. Or at least - doing so would
require multiple passes over the fstab data (as well as looking at existing
mount units), and potentially doing multi-phase generation. I'm not sure it's
worth doing that without a real world use case. For now, this will fix at least
the OSTree + `/home` <https://bugzilla.redhat.com/show_bug.cgi?id=1382873> case
mentioned above, and in general anyone who for whatever reason has symlinks in
their `/etc/fstab`.

(cherry picked from commit 634735b)

Resolves: RHEL-17394
    @cgwalters @brozs
    cgwalters authored and brozs committed Nov 27, 2023
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  2. call chase_symlinks without the /sysroot prefix (#6411) 

    In case fstab-generator is called in the initrd, chase_symlinks()
returns with a canonical path "/sysroot/sysroot/<mountpoint>", if the
"/sysroot" prefix is present in the path.

This patch skips the "/sysroot" prefix for the chase_symlinks() call,
because "/sysroot" is already the root directory and chase_symlinks()
prepends the root directory in the canonical path returned.

(cherry picked from commit 98eda38)

Related: RHEL-17394
    @haraldh @brozs
    haraldh authored and brozs committed Nov 27, 2023
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  3. fstab-generator: downgrade message when we can't canonicalize fstab e… 

    …ntries (#8281)

Let's make this LOG_DEBUG, as this didn't used to be an issue, and
shouldn't really be still.

Replaces: #8132
(cherry picked from commit f1a2c75)

Related: RHEL-17394
    @poettering @brozs
    poettering authored and brozs committed Nov 27, 2023
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  4. Add $SYSTEMD_IN_INITRD=yes|no override for debugging 

    Based on: 0307ea4
Related: RHEL-17394

rhel-only
    @mrc0mmand
    mrc0mmand committed Nov 27, 2023
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  5. escape: call unit_name_is_valid() with correct flags 

    Otherwise --template= simply doesn't work:

$ ./systemd-escape --template=systemd-mkfs@.service --path /dev/test9
is_valid: 0
is_template: 1
Template name systemd-mkfs@.service is not valid.

Related: RHEL-17394

rhel-only
    @mrc0mmand
    mrc0mmand committed Nov 27, 2023
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  6. fstab-generator: fix ordering of /sysroot/usr mount 

    According to bootup(7) and the behavior when /usr is specified in /etc/fstab, the /sysroot/usr mount should be before initrd-fs.target, not before initrd-root-fs.target.

Related: RHEL-17394

(cherry picked from commit 104bc12)
    @nmartensen @mrc0mmand
    nmartensen authored and mrc0mmand committed Nov 27, 2023
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  7. test: backport TEST-81-GENERATORS (fstab-generator only) 

    Some fstab-generator features are not present on RHEL 7 or they behave
differently - in such case there's an inline comment explaining what's
different with a reference to an upstream commit that introduced the
changed behavior.

Also, RHEL 7 systemd doesn't allow overriding (/sysroot)/etc/fstab or
/proc/cmdline, so instead of backporting another bunch of potential
risky commits, let's temporarily bind-mount a modified copy of necessary
files in place of the expected ones. One exception is
$SYSTEMD_IN_INITRD, since systemd checks if the mount for / is a tmpfs,
which is a pain to mock, but the patch for that is, thankfully, pretty
small.

Related: RHEL-17394

rhel-only
    @mrc0mmand
    mrc0mmand committed Nov 27, 2023
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