[Tip] fast reboots with kexec

morph027 · Jul 11, 2017

Install the package:

Code:

echo "kexec-tools kexec-tools/load_kexec boolean false" | debconf-set-selections
apt-get -y install kexec-tools

Create /etc/systemd/system/kexec-pve.service with content:

Code:

[Unit]
Description=boot into into the current pve kernel
Documentation=man:kexec(8)
DefaultDependencies=no
Before=shutdown.target umount.target final.target

[Service]
Type=oneshot
ExecStart=/sbin/kexec -l /boot/pve/vmlinuz --initrd=/boot/pve/initrd.img --reuse-cmdline

[Install]
WantedBy=kexec.target

Enable:

Code:

systemctl enable kexec-pve.service

Now you can reboot without the whole UEFI/BIOS/OpROM stuff with

Code:

systemctl kexec

neonmaus · Jul 24, 2017

Thanks for this very good tip

bogo22 · Aug 15, 2017

Really nice, thanks. The proxmox dev's should integrate it and make it as alternative reboot option to the "real" reboot with bios

Small nit: Is the "into into" in the description right?

homozavrus · Aug 18, 2017

Thanks, work like a charm!

Better to place this thread as page in wiki

Rhinox · Aug 18, 2017

morph027 said:
Description=boot into into the current pve kernel

Just to make things clear: it does not boot into the current (running) kernel, but into the kernel defined as primary in boot-loader. So if kernel was updated, it boots into the new one...

eXtremeSHOk · Apr 7, 2018

Thanks for the heads up,

I have added this to the Post Install Script (postinstall.sh) located at https://github.com/extremeshok/xshok-proxmox

Which adds the 'reboot-quick' command

fireon · Apr 7, 2018

Rhinox said:
Just to make things clear: it does not boot into the current (running) kernel, but into the kernel defined as primary in boot-loader. So if kernel was updated, it boots into the new one...

Not it boots into current kernel. Because there is no grub at kexec. Tested here on my two machines.

morph027 · Apr 7, 2018

In fact, it is loading /boot/pve/vmlinuz with /boot/pve/initrd.img which is a symlink to the latest installed kernel.

Code:

root@proxmox:~# cat /etc/systemd/system/kexec-pve.service
[Unit]
Description=boot into into the current pve kernel
Documentation=man:kexec(8)
DefaultDependencies=no
Before=shutdown.target umount.target final.target

[Service]
Type=oneshot
ExecStart=/sbin/kexec -l /boot/pve/vmlinuz --initrd=/boot/pve/initrd.img --reuse-cmdline

[Install]
WantedBy=kexec.target
root@proxmox:~# ls -la /boot/pve/
total 20
drwxr-xr-x 2 root root  8 Apr  3 11:30 .
drwxr-xr-x 5 root root 15 Apr  5 08:50 ..
lrwxrwxrwx 1 root root 25 Apr  3 11:30 initrd.img -> /boot/pve/initrd.img-4.13
lrwxrwxrwx 1 root root 30 Apr  3 11:30 initrd.img-4.13 -> /boot/initrd.img-4.13.16-1-pve
lrwxrwxrwx 1 root root 30 Mar 27 08:20 initrd.img-4.15 -> /boot/initrd.img-4.15.10-1-pve
lrwxrwxrwx 1 root root 22 Apr  3 11:30 vmlinuz -> /boot/pve/vmlinuz-4.13
lrwxrwxrwx 1 root root 27 Apr  3 11:30 vmlinuz-4.13 -> /boot/vmlinuz-4.13.16-1-pve
lrwxrwxrwx 1 root root 27 Mar 27 08:20 vmlinuz-4.15 -> /boot/vmlinuz-4.15.10-1-pve

fireon · Apr 7, 2018

Strange, this day i've installed 4.15

Code:

total 20
drwxr-xr-x 2 root root  8 Apr  7 13:29 ./
drwxr-xr-x 5 root root 19 Apr  7 13:29 ../
lrwxrwxrwx 1 root root 25 Mar 26 23:16 initrd.img -> /boot/pve/initrd.img-4.13
lrwxrwxrwx 1 root root 30 Apr  4 21:21 initrd.img-4.13 -> /boot/initrd.img-4.13.16-1-pve
lrwxrwxrwx 1 root root 30 Apr  7 13:29 initrd.img-4.15 -> /boot/initrd.img-4.15.10-1-pve
lrwxrwxrwx 1 root root 22 Mar 26 23:16 vmlinuz -> /boot/pve/vmlinuz-4.13
lrwxrwxrwx 1 root root 27 Apr  4 21:21 vmlinuz-4.13 -> /boot/vmlinuz-4.13.16-1-pve
lrwxrwxrwx 1 root root 27 Apr  7 13:29 vmlinuz-4.15 -> /boot/vmlinuz-4.15.10-1-pve

You see default is 4.13. But yes i can force manualy with an other line

Code:

ExecStart=/sbin/kexec -l /boot/pve/vmlinuz-4.15 --initrd=/boot/pve/initrd.img-4.15 --reuse-cmdline

morph027 · Apr 9, 2018

Jip, same here. Probably because it's a beta kernel..

fabian · Apr 9, 2018

morph027 said:
Jip, same here. Probably because it's a beta kernel..

correct.

fireon · Apr 9, 2018

Ah ok, thanks.

homozavrus · Apr 17, 2018

eXtremeSHOk said:
Thanks for the heads up,

I have added this to the Post Install Script (postinstall.sh) located at https://github.com/extremeshok/xshok-proxmox

Which adds the 'reboot-quick' command

there is no script in repo

eXtremeSHOk · Apr 18, 2018

homozavrus said:
there is no script in repo

Script was renamed to install-post.sh

javii · Jul 31, 2019

Hi, have you tried with Proxmox 6? I have tried but it says:

# systemctl kexec
Cannot find the ESP partition mount point.

morph027 · Jul 31, 2019

This indicates you need to load a kernel into kexec.

Code:

systemctl start kexec-pve.service

If you want to use it anytime, just issue a

Code:

systemctl enable kexec-pve.service

javii · Jul 31, 2019

Hi, it works when I start the service, but I have to start the service manually after reboot, even the service is enabled:

Code:

root@xxxxxxxx:~# uptime
 13:44:03 up 1 min,  2 users,  load average: 0.20, 0.12, 0.04

root@xxxxxxxx:~# systemctl kexec
Cannot find the ESP partition mount point.

root@cxxxxxxxx:~# systemctl is-enabled kexec-pve.service
enabled

root@xxxxxxxx:~# systemctl status kexec
● kexec.service - LSB: Execute the kexec -e command to reboot system
   Loaded: loaded (/etc/init.d/kexec; generated)
   Active: active (exited) since Wed 2019-07-31 13:42:13 CEST; 1min 33s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 1699 ExecStart=/etc/init.d/kexec start (code=exited, status=0/SUCCESS)

Jul 31 13:42:13 xxxxxxxx systemd[1]: Starting LSB: Execute the kexec -e command to reboot system...
Jul 31 13:42:13 xxxxxxxx systemd[1]: Started LSB: Execute the kexec -e command to reboot system.

root@xxxxxxxx:~# systemctl start kexec-pve.service

root@xxxxxxxx:~# systemctl status kexec
● kexec.service - LSB: Execute the kexec -e command to reboot system
   Loaded: loaded (/etc/init.d/kexec; generated)
   Active: active (exited) since Wed 2019-07-31 13:42:13 CEST; 2min 2s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 1699 ExecStart=/etc/init.d/kexec start (code=exited, status=0/SUCCESS)

Jul 31 13:42:13 xxxxxxxx systemd[1]: Starting LSB: Execute the kexec -e command to reboot system...
Jul 31 13:42:13 xxxxxxxx systemd[1]: Started LSB: Execute the kexec -e command to reboot system.

root@xxxxxxxx:~# systemctl kexec
Connection to xxxxxxxx closed by remote host.
Connection to xxxxxxxx closed.

Thank you for your help

morph027 · Jul 31, 2019

Hm, probably a timing issue....i do have a brand new PVE6 test lab installation right now and will check if i can reproduce this.

javii · Jul 31, 2019

morph027 said:
Hm, probably a timing issue....i do have a brand new PVE6 test lab installation right now and will check if i can reproduce this.

Great! Thank you!

morph027 · Aug 4, 2019

Jip, you're right, it's not working without another call to start kexec-pve.service ... will look into this.

[Tip] fast reboots with kexec

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