On Sun, Oct 19, 2014 at 10:36:23PM +0200, Jimmy Thrasibule wrote: > Hello, > > I wonder if one can avoid a complete reboot of the system just by > halting the operating system but right after load the initramfs and > restart from there? I don't think you can quite do what you're thinking, but there are other ways around it. > > Basically when we reboot, we only want to reset the operating system > state but rarely to do all the hardware checks again. And for a kernel > update, there is kexec. If you've got as far as halting the system, then kexec or a full reboot are your only options. This is due to the fact that you've unmounted all the block devices, probably powered them off and so on. I guess you could try jumping back into an initramfs (that you loaded into memory before shutdown), but you might as well reset the kernel at that point. It'll only take a few seconds more. The other alternative, for a "lighter" reboot is to drop to runlevel 1 (or single-user.target, in systemd's parlance). This will stop all the mutli-user services (X, httpd, sshd and so on) and bring you to a point where only a minimal number of services are running (file systems are mounted, the local console is active and so on). You could use "checkrestart" (from the debian-goodies package) to check what remaining services are using outdated libraries and restart them manually. At this point, you can come back up to runlevel 2-5 (systemd: multi-user.target) in order to bring the system back up to full capacity. I think it depends on what you're trying to achieve and what you're trying to avoid.
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