vmcp - Send CP commands to the z/VM hypervisor

6.10 z/VM guest

Use the vmcp command to send control program (CP) commands to the z/VM® hypervisor and display the response from z/VM.

The vmcp command expects the command line as a parameter and returns the response to stdout. Error messages are written to stderr.

You can issue CP commands through the /dev/vmcp device node or with the vmcp command. In both cases, the vmcp module must be compiled into the kernel.

vmcp syntax

Where:

-k or --keepcase: preserves the case of the characters in the specified command string. By default, the command string is converted to uppercase characters.
-b <size> or --buffer=<size>: specifies the buffer size in bytes for the response from z/VM CP. Valid values are from 4096 (or 4k) up to 1048756 (or 1M). By default, vmcp allocates an 8192 byte (8k) buffer. You can use k and M to specify kilo- and megabytes. The suffixes are not case sensitive, so k is equivalent to K and m is equivalent to M.
<command>: specifies the command that you want to send to CP.
-h or --help: displays help information. To view the man page, enter man vmcp.
-v or --version: displays version information.

If the command completes successfully, vmcp returns 0. Otherwise, vmcp returns one of the following values:

CP returned a non-zero response code.
The specified buffer was not large enough to hold CP's response. The command was run, but the response was truncated. You can use the --buffer option to increase the response buffer.
Linux® reported an error to vmcp. See the error message for details.
The options that are passed to vmcp were erroneous. See the error messages for details.

Examples

To get your user ID issue:
```
# vmcp query userid 
```
To attach the device 1234 to your guest, issue:
```
# vmcp attach 1234 \*
```
If you add the following line to /etc/sudoers:
```
ALL ALL=NOPASSWD:/sbin/vmcp indicate
```
every user on the system can run the indicate command by using:
```
# sudo vmcp indicate
```
If you need a larger response buffer, use the --buffer option:
```
# vmcp --buffer=128k q 1-ffff
```