fix(kernel-modules): Add sysctl to initramfs to handle modprobe files

[Conan-Kudo]

This pull request changes...

Changes

dracut-systemd module now will incorporate sysctl into initramfs so that modprobe configuration files that call sysctl will function properly.

Checklist

• I have tested it locally
• I have reviewed and updated any documentation if relevant
• I am providing new code and test(s) for it

[johannbg]

We already have a systemd sysctl module so adding this to dracut-systemd module should not be necessary. What usecase does this solve which is not solved by including that module?

[Conan-Kudo]

The systemd-sysctl module doesn't use the sysctl binary, whereas this one will because various modprobe.d config files can use it. For example:

./etc/modprobe.d/firewalld-sysctls.conf:install nf_conntrack /sbin/modprobe --ignore-install nf_conntrack $CMDLINE_OPTS && /sbin/sysctl --quiet --pattern 'net[.]netfilter[.]nf_conntrack.*' --system
./usr/lib/modprobe.d/50-nfs.conf:install sunrpc /sbin/modprobe --ignore-install sunrpc $CMDLINE_OPTS && { /sbin/sysctl -q --pattern sunrpc --system; exit 0; }
./usr/lib/modprobe.d/50-nfs.conf:install rpcrdma /sbin/modprobe --ignore-install rpcrdma $CMDLINE_OPTS && { /sbin/sysctl -q --pattern sunrpc.svc_rdma --system; exit 0; }
./usr/lib/modprobe.d/50-nfs.conf:install lockd /sbin/modprobe --ignore-install lockd $CMDLINE_OPTS && { /sbin/sysctl -q --pattern fs.nfs.n[sl]m --system; exit 0; }
./usr/lib/modprobe.d/50-nfs.conf:install nfsv4 /sbin/modprobe --ignore-install nfsv4 $CMDLINE_OPTS && { /sbin/sysctl -q --pattern 'fs.nfs.(nfs_callback_tcpport|idmap_cache_timeout)' --system; exit 0; }
./usr/lib/modprobe.d/50-nfs.conf:install nfs /sbin/modprobe --ignore-install nfs $CMDLINE_OPTS && { /sbin/sysctl -q --pattern fs.nfs --system; exit 0; }

[johannbg]

If this gets added it belongs in the systemd sysctl module not in the dracut systemd module.

[Conan-Kudo]

Obviously I could add it there and it'd coincidentally work, but the systemd-sysctl module isn't where the breakage is occurring. It makes sense to me to add the binary in the module that winds up invoking the tool.

[johannbg]

Arguably the modules that require sysctl be invoked in the firstplace are broken and those should be fixed so there is high probably this gets nacked

[iammattcoleman]

Arguably the modules that require sysctl be invoked in the firstplace are broken and those should be fixed so there is high probably this gets nacked

While I agree with this philosophically, the practical reality is that systemd-sysctl is not universally adopted. To try to dictate that every other distribution and creator of modprobe drop-in config files needs to use it seems like an uphill battle.

[LaszloGombos]

How do you all feel about adding sysctl to the kernel-modules dracut module as an optional dependency ?
If usage of sysctl is indeed modprobe related, than kernel-modules could be a better home for this as kernel-modules dracut module is responsible for installing the modprobe *.conf files into initrd.

[johannbg]

Arguably the modules that require sysctl be invoked in the firstplace are broken and those should be fixed so there is high probably this gets nacked

While I agree with this philosophically, the practical reality is that systemd-sysctl is not universally adopted. To try to dictate that every other distribution and creator of modprobe drop-in config files needs to use it seems like an uphill battle.

We make the assumption that distribution that adopted systemd did so wholesale trying to support ca 250 systemd based distribution that randomly decided which component of systemd it uses is madness.

[johannbg]

How do you all feel about adding sysctl to the kernel-modules dracut module as an optional dependency ? If usage of sysctl is indeed modprobe related, than kernel-modules could be a better home for this as kernel-modules dracut module is responsible for installing the modprobe *.conf files into initrd.

That's an ack from me.

[Conan-Kudo]

I'm fine with that too, that's where I initially thought to do it, but when I did the search for what loaded the files, this module came up instead.

[Conan-Kudo]

@LaszloGombos I just moved it over to the kernel-modules module now.

[LaszloGombos]

lgtm

[LaszloGombos]

Perhaps once this PR lands, we no longer need this code in the test - 4a5785a..