Raymund Will <r...@suse.de> writes: > Hi, > > please let me try to add a bit of context and explain three IMHO > crucial points of the proposed patch. > > First, it is meant to work without any changes to config-files > on 'linux'-systems, simply by calling `grub-emu --kexec`. > And, called this way, it actually uses `systemctl kexec` exclusively > to instruct `systemd` to perform the "kexec"-reboot in a sane and > safe manner. > > Second, it only supports a very limited set of commands in `grub.cfg`, > as `grub-emu` can not implement the full functionality of a firmware- > loaded `grub` binary (like raw-device access) and it hinges massively > on proper `kexec`-support from the machine/firmware, so unfortunately > it won't be universally useful, > > Third, for use in a "pre-boot environment" (i.e. initrd/chroot), which > has full control over it's state, but no (fully) working `systemd`, > a call to `grub-emu --kexec --kexec` changes the behavior to allow a > fall-forward to `kexec -e`. As a safe-guard for the adventurously > minded `systemctl kexec` is still tried first! > > This third point describes the use-case the original patch-set was > developed for and the second doesn't hurt (much) on the systems it > is deployed/used in the field. But the first was found to be really > useful, especially on machines, which can reliably `kexec`, but are > dead slow through cold-boot (think "huge memory", "tons of devices") > and/or have "exotic" console setups ("3215" anybody?). Note that, > as the boot configuration (namely `grub.cfg`) wasn't changed, regular > boot can't be affected by this short-cut (particularly, when `kexec` > might have failed). > > Granted, the duplication of `--kexec` to signify "force it", might > as well be spelled out as `--force-kexec` (or something similar). > (But that change will provoke inconsistencies during an indefinite > migration phase, where pre-boot images don't match binaries in the > root filesystem, notably, when rollback snapshots come into play.)
Passing --kexec twice (or --force-kexec) doesn't appear to change anything in the versions of this patch I can easily find. We could add the behavior you're describing though - Daniel, would that help with your concerns about it? > Config-overrides in `grub.cfg` in turn would be a nice addition, but > are relatively expensive to implement, as they'd probably need to be > parsed and split into an array for `grub_util_exec()`, right? Yes. It's inevitably best-effort, especially if we can't depend on a working shell. > But, please, still leave sane defaults in the binary, for out-of- > the-box, no-config-changes-necessary usage, pretty please! > > Would it be possible to re-evaluate the proposed patch with this > in mind? > > PS: in light of my statements above, the "description" of this > patch definitely needs re-wording... Any interest in doing that, or should I? Be well, --Robbie
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