I have a prodlem with disable sysrq. I had done follow actions but it didn't help.

1) # grep "SYSRQ" /boot/config-$(uname -r)
CONFIG_MAGIC_SYSRQ=y
CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE=0x0
# CONFIG_MAGIC_SYSRQ_SERIAL is not set

2) # sysctl -a | grep sysrq
kernel.sysrq = 0

3) # cat /etc/sysctl.conf | grep sysrq
kernel.sysrq = 0

4) # cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-5.14.21-at154.148.1-default root=/dev/mapper/system-root rw systemd.show_status=1 console=ttyS0,115200 console=tty0 init_on_alloc=1 iommu=force iommu.strict=1 iommu.passthrough=0 randomize_kstack_offset=1 vsyscall=none debugfs=no-mount tsx=off splash=silent resume=/dev/system/swap preempt=full mitigations=auto quiet security=apparmor

But when I do
# echo o > /proc/sysrq-trigger
The machime immediately powers off

Have somebody faced with it and can help?

You want

I tried it. It dosen't help. echo o > /proc/sysrq-trigger will be work.

# cat /proc/sys/kernel/sysrq
0

You can't. Invocation via /proc/sysrq-trigger is always allowed, configuration options affect only the the key itself.

Are there opportunity disable sysrq-trigger, maybe it can be disabled with kernel?
I followed https://www.kernel.org/doc/html/late...ide/sysrq.html

This very page says the same: "Note that the value of /proc/sys/kernel/sysrq influences only the invocation via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always allowed (by a user with admin privileges)." Apart from patching the kernel nothing can done.

1 members found this post helpful.

thanx.
I didn't pay attention

TryBut why? Only root can write to /proc/sysrq-trigger.

I tried it but when kernel builds the value changes to "y". According guide you can manage it changing CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE.

There is something wrong in your kernel building process if it changes CONFIG_MAGIC_SYSRQ to "y". It does not do it here, and the new kernel does not have /proc/sysrq-trigger or /proc/sys/kernel/sysrq.

If you compile in the Magic SysRq key support (CONFIG_MAGIC_SYSRQ=y) then you can set the default value of /proc/sys/kernel/sysrq using CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE.

1 members found this post helpful.

I found why it could not be set "# CONFIG_MAGIC_SYSRQ is not set" because for it you need also disable "# CONFIG_KGDB is not set" only after it you can disable CONFIG_MAGIC_SYSRQ

thank everyone