Using the magic sysrequest feature

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest KVM guest

The Linux® on IBM® Z terminal device drivers support the magic sysrequest functions.

To call the magic sysrequest functions on the VT220 terminal or on hvc0, enter the single character Ctrl+o followed by the character for the particular function.
You can call the magic sysrequest functions from the hvc0 terminal device if it is present and is activated to receive Linux kernel messages.
To call the magic sysrequest functions on a line-mode terminal, enter the 2 characters ^- (caret and hyphen) followed by a third character that specifies the particular function.

Table 1 provides an overview of the commands for the magic sysrequest functions:

Table 1. Magic sysrequest functions
On line-mode terminals, enter	On hvc0 and the VT220 terminal, enter	To
`^-b`	`b`	Re-IPL immediately.
`^-s`	`s`	Emergency sync all file systems.
`^-u`	`u`	Emergency remount all mounted file systems read-only.
`^-t`	`t`	Show task info.
`^-m`	`m`	Show memory.
`^-` followed by a digit (0 - 9)	followed by a digit (0 - 9)	Set the console log level.
`^-e`	`e`	Send the TERM signal to end all tasks except init.
`^-i`	`i`	Send the KILL signal to end all tasks except init.
`^-p`	`p`	Obtain debug information about the CPU-measurement counter facility.

Note: In Table 1 Ctrl+o

means pressing

while holding down the control key.

Table 1 lists the main magic sysrequest functions that are known to work on Red Hat® Enterprise Linux 9.2. For a more comprehensive list of functions, see Documentation/sysrq.txt in the Linux source tree. Some of the listed functions might not work on your system.