table of contents
hvc_iucv(9) | z/VM IUCV HVC device driver | hvc_iucv(9) |
NAME¶
hvc_iucv - Introduction to the z/VM IUCV hypervisor console (HVC) device driverSYNOPSIS¶
hvc_iucv=numberDESCRIPTION¶
The Hypervisor Console (HVC) device driver is a generic TTY device driver providing terminal devices with pluggable transport device drivers.USAGE¶
Connecting to z/VM IUCV HVC terminal devices¶
Connections to z/VM IUCV HVC terminal devices are established with the IUCV terminal application iucvconn(1). To connect to the first z/VM IUCV HVC terminal device on the z/VM guest virtual machine "LNX1234", run:iucvconn LNX1234 lnxhvc0
The lnxhvcn identifier refers to the IUCV name of z/VM IUCV HVC terminal devices; where n corresponds to the terminal device number. For z/VM IUCV HVC terminal devices, iucvconn(1) does not set the terminal environment. See section "Setting up the terminal environment" below for further instructions. The terminal connection is disconnected if the terminal session ends by logging off (for example, by typing exit). Alternatively, iucvconn(1) provides an escape function for disconnecting from the terminal at any time. See also the manual page of iucvconn(1).
- Note:
- If the first z/VM HVC terminal device is configured as the preferred Linux console, a logoff might be followed by a new login prompt. End the terminal session by using the disconnect escape function. Reconnecting always resumes the existing terminal session. Explicitly logging off before using the disconnect escape function assures that users must log in again.
Using the magic sysrequest function on the first z/VM IUCV HVC terminal¶
The first z/VM IUCV HVC terminal, which can be used as Linux console, supports the "magic sysrequest" function if the Linux kernel has been built with CONFIG_MAGIC_SYSRQ. To invoke the "magic sysrequest" function, press "Ctrl+o" followed by a second character that designates the debugging or emergency function. The most important magic sysrequest functions are:- 0 .. 9
- Set the Linux console log level and control which kernel message are written to Linux console devices.
- b
- Re-IPL immediately (without syncing or unmounting file systems). The re-IPL configuration is used for the re-IPL of the Linux system.
- s
- Emergency sync all file file systems.
- u
- Emergency remount all mounted file systems read-only.
- t
- Show task info.
- m
- Show memory.
- e
- Send the TERM signal to end all tasks except init(8).
- i
- Send the KILL signal to end all tasks except init(8).
CONFIGURATION¶
Using the z/VM IUCV HVC terminal device as Linux console¶
The first z/VM IUCV HVC terminal device can display kernel messages and it can also be used as the preferred Linux console (i.e. become /dev/console). The preferred console is used as the initial input and output device, beginning at the stage of the boot process when the init(8) program is called. Messages issued by programs that run at this stage are only displayed on the preferred console.- Note:
- Console messages are not displayed if the z/VM IUCV HVC terminal is not connected. If console messages flood the terminal, the z/VM HVC terminal device driver might discard console messages if they come in too fast.
- Note:
- The last console= parameter designates the device for use as the preferred console. For Linux on System z, the default preferred console device is ttyS0.
Restricting terminal connections using a z/VM user ID filter¶
The z/VM IUCV HVC device driver can filter incoming connection requests based on the user ID of the originating z/VM guest virtual machine.- Note:
- If z/VM user ID filtering is active, connection attempts from the z/VM guest virtual machine to itself are also subject to filtering. If the local z/VM user ID is not listed, local connection requests are refused.
Configuring HVC terminals for user logins¶
Typically, getty programs initialize terminals and prepare terminals for user logins.h0:2345:respawn:/sbin/mingetty hvc0
Add new entries for each HVC terminal device that is designated for user logins. You can use ttyrun(8) to start a getty program on each HVC terminal device and to prevent respawns through the init(8) program when a HVC terminal is not available. You can then change the number of HVC terminal devices without adding or removing entries every time.
Setting up HVC terminals for root logins¶
To allow root logins on HVC terminals, ensure that the respective terminal device names are listed in /etc/securetty(5). HVC terminal device names start with hvc followed by an integer in the range 0 to 7.Setting up the terminal environment¶
The terminal environment is changed by assigning the terminal name to the TERM environment variable. This can be done manually, or by a getty program.- 1.
- To display the current terminal name, issue the command:
user@host:~$ echo $TERM xterm
- 2.
- To connect to a z/VM IUCV HVC terminal, run
iucvconn(1) and log in as usual:
user@host:~$ iucvconn MYLNX01 lnxhvc0 ... user@MYLNX01:~$
- 3.
- To assign the terminal name from step 1. to the terminal
environment variable, issue the following command:
user@MYLNX01:~$ export TERM=xterm
h0:2345:respawn:/sbin/agetty -L 9600 hvc0 linux
DIAGNOSTICS¶
The z/VM IUCV hypervisor console device driver uses the kernel message infrastructure for its messages. The message prefix is hvc_iucv.SEE ALSO¶
iucvconn(1), chiucvallow(8), af_iucv(7), bootparam(7), inittab(5), getty(8), agetty(8), mingetty(8), ttyrun(8), login(1), securetty(5)July 2010 | s390-tools |