Re: [gentoo-user] Re: How to poweroff the system from user?

[Tom H <tomh0665@gmail.com>]

On Tue, Mar 31, 2015 at 1:57 AM, Fernando Rodriguez
<frodriguez.developer@outlook.com> wrote:


> On Linux now there's the Magic SysRq Key feature for that. If enabled (I think
> it is by default, may be wrong) you can use ctrl-alt-sysrq plus one these keys
> even if your kernel panics or freezes in most cases (ctrl may only be needed
> from xorg):
>
> r - to get the keyboard back so you can switch to VT if xorg freezes
> e - to terminate all processes gracefully (SIGTERM) except pid 1
> i - to terminate all processes forcefully (SIGKILL) except pid 1
> s - to sync all filesystems
> u - to unmount them and remount readonly
> b - to reboot

You have to set "MAGIC_SYSRQ" to "y" for it to be enabled.

You can set the "capabilities" of sysrq either via
'MAGIC_SYSRQ_DEFAULT_ENABLE" or via sysctl. Debian uses the former (to
set it to 438) and Ubuntu and Fedora use the latter (to set it to 176
and 16 respectively). "16" is systemd upstream's default whereby you
can only sync filesystems. It's the kind of value that can be the
source of a lot of arguing...


> Easy to remember as "Reboot Even If System Utterly Broken"

I remember it as the reverse of "busier".