On 09.10.2014 16:08, Lennart Poettering wrote: > On Thu, 09.10.14 09:37, Tobias Hunger (tobias.hun...@gmail.com) wrote: > >> On Oct 8, 2014 2:15 PM, "Harald Hoyer" <harald.ho...@gmail.com> wrote: >>>> What is the rationale of this patch? >>>> Supporting systems without /etc/fstab in the root device? >>>> Overriding the /etc/fstab settings? >>>> >>>> In a systemd initrd (e.g. in dracut) as soon as initrd-root-fs.target is >>>> reached, initrd-parse-etc.service is executed, which retriggers the >>>> fstab-generator and reads fstab from the real root and generates units >> for /usr. >> >> Hello Harald, >> >> The use case is exactly the one Lennart described in his blog about >> deploying Linux in the future. >> >> My setup now looks like this: I got a Btrfs partition for my Linux >> installations. This partition has a subvol root:somename:someid:x86_64 >> containing a Linux installation minus /use. >> >> Then I have several versions of /use for that distribution in more >> subvolumes named usr:someid:x86_64:version (all with different versions, >> basically getting incremented whenever a new set of packages gets >> installed). >> >> The idea is to now be able to write bootloader entries for all versions the >> somename-installation. >> >> For that the initrd needs to know which /usr to mount on top of the root >> partition. >> >> I can not use the fstab from the root drive here, because that would always >> point to the same version of /use, preventing me to roll back/forward when >> something breaks during an upgrade. >> >> What I could do instead is to put the information about which subvol to >> mount at /use into the initrd. But I actually think the way of passing this >> into initrd in the same way as the rootfs is more consistent and it also >> saves me from having a new initrd in /boot when libreoffice gets updated. >> That *might* be necessary when using secure boot, but only then. >> >> Does this explain my motivation for this patch sufficiently? > > Hmm, so I think this should be merged, but I'd like to ask for one > more change. We really want to avoid inventing new non-namespaced > kernel command line options, that's really something we should leave > to the kernel guys... > > Hence, I'd propose using "mount.usr=", "mount.usrflags=" and > "mount.usrfstype="... Or maybe "fs." as prefix? Or "mnt."? But I think > "mount." is the nicest one, even if it is slightly more to type. > > Hope that make sense? > > (OTOH I just yesterday merged a patch that introduced a new > un-namespaced kernel cmdline option "rescue", so I am not totall fair > here, but I think that's a special case...) > > Lennart >
Just be careful choosing the prefix. It must not be the name of a kernel module, otherwise this kernel module is presented with all those options, which might freak out that module. I accidentally chose "rd." not knowing that "rd" is a module alias for the brd kernel module. Just check with a recent kernel: # modinfo "<prefix>" I have the feeling, we should somehow register a namespace for userspace on the kernel command line or have global list. :-/ I just don't want to end with something like org.freedesktop.systemd.log_level=... :-) _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
