568 lines
23 KiB
Plaintext
568 lines
23 KiB
Plaintext
===========================================================================
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HVCS
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IBM "Hypervisor Virtual Console Server" Installation Guide
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for Linux Kernel 2.6.4+
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Copyright (C) 2004 IBM Corporation
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===========================================================================
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NOTE:Eight space tabs are the optimum editor setting for reading this file.
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===========================================================================
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Author(s) : Ryan S. Arnold <rsa@us.ibm.com>
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Date Created: March, 02, 2004
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Last Changed: August, 24, 2004
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---------------------------------------------------------------------------
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Table of contents:
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1. Driver Introduction:
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2. System Requirements
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3. Build Options:
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3.1 Built-in:
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3.2 Module:
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4. Installation:
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5. Connection:
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6. Disconnection:
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7. Configuration:
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8. Questions & Answers:
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9. Reporting Bugs:
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---------------------------------------------------------------------------
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1. Driver Introduction:
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This is the device driver for the IBM Hypervisor Virtual Console Server,
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"hvcs". The IBM hvcs provides a tty driver interface to allow Linux user
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space applications access to the system consoles of logically partitioned
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operating systems (Linux and AIX) running on the same partitioned Power5
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ppc64 system. Physical hardware consoles per partition are not practical
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on this hardware so system consoles are accessed by this driver using
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firmware interfaces to virtual terminal devices.
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---------------------------------------------------------------------------
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2. System Requirements:
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This device driver was written using 2.6.4 Linux kernel APIs and will only
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build and run on kernels of this version or later.
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This driver was written to operate solely on IBM Power5 ppc64 hardware
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though some care was taken to abstract the architecture dependent firmware
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calls from the driver code.
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Sysfs must be mounted on the system so that the user can determine which
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major and minor numbers are associated with each vty-server. Directions
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for sysfs mounting are outside the scope of this document.
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---------------------------------------------------------------------------
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3. Build Options:
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The hvcs driver registers itself as a tty driver. The tty layer
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dynamically allocates a block of major and minor numbers in a quantity
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requested by the registering driver. The hvcs driver asks the tty layer
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for 64 of these major/minor numbers by default to use for hvcs device node
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entries.
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If the default number of device entries is adequate then this driver can be
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built into the kernel. If not, the default can be over-ridden by inserting
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the driver as a module with insmod parameters.
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---------------------------------------------------------------------------
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3.1 Built-in:
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The following menuconfig example demonstrates selecting to build this
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driver into the kernel.
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Device Drivers --->
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Character devices --->
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<*> IBM Hypervisor Virtual Console Server Support
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Begin the kernel make process.
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---------------------------------------------------------------------------
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3.2 Module:
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The following menuconfig example demonstrates selecting to build this
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driver as a kernel module.
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Device Drivers --->
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Character devices --->
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<M> IBM Hypervisor Virtual Console Server Support
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The make process will build the following kernel modules:
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hvcs.ko
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hvcserver.ko
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To insert the module with the default allocation execute the following
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commands in the order they appear:
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insmod hvcserver.ko
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insmod hvcs.ko
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The hvcserver module contains architecture specific firmware calls and must
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be inserted first, otherwise the hvcs module will not find some of the
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symbols it expects.
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To override the default use an insmod parameter as follows (requesting 4
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tty devices as an example):
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insmod hvcs.ko hvcs_parm_num_devs=4
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There is a maximum number of dev entries that can be specified on insmod.
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We think that 1024 is currently a decent maximum number of server adapters
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to allow. This can always be changed by modifying the constant in the
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source file before building.
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NOTE: The length of time it takes to insmod the driver seems to be related
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to the number of tty interfaces the registering driver requests.
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In order to remove the driver module execute the following command:
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rmmod hvcs.ko
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The recommended method for installing hvcs as a module is to use depmod to
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build a current modules.dep file in /lib/modules/`uname -r` and then
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execute:
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modprobe hvcs hvcs_parm_num_devs=4
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The modules.dep file indicates that hvcserver.ko needs to be inserted
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before hvcs.ko and modprobe uses this file to smartly insert the modules in
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the proper order.
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The following modprobe command is used to remove hvcs and hvcserver in the
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proper order:
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modprobe -r hvcs
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---------------------------------------------------------------------------
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4. Installation:
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The tty layer creates sysfs entries which contain the major and minor
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numbers allocated for the hvcs driver. The following snippet of "tree"
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output of the sysfs directory shows where these numbers are presented:
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sys/
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|-- *other sysfs base dirs*
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|-- class
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| |-- *other classes of devices*
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| `-- tty
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| |-- *other tty devices*
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| |-- hvcs0
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| | `-- dev
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| |-- hvcs1
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| | `-- dev
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| |-- hvcs2
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| | `-- dev
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| |-- hvcs3
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| | `-- dev
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| |-- *other tty devices*
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|-- *other sysfs base dirs*
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For the above examples the following output is a result of cat'ing the
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"dev" entry in the hvcs directory:
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Pow5:/sys/class/tty/hvcs0/ # cat dev
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254:0
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Pow5:/sys/class/tty/hvcs1/ # cat dev
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254:1
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Pow5:/sys/class/tty/hvcs2/ # cat dev
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254:2
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Pow5:/sys/class/tty/hvcs3/ # cat dev
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254:3
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The output from reading the "dev" attribute is the char device major and
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minor numbers that the tty layer has allocated for this driver's use. Most
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systems running hvcs will already have the device entries created or udev
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will do it automatically.
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Given the example output above, to manually create a /dev/hvcs* node entry
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mknod can be used as follows:
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mknod /dev/hvcs0 c 254 0
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mknod /dev/hvcs1 c 254 1
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mknod /dev/hvcs2 c 254 2
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mknod /dev/hvcs3 c 254 3
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Using mknod to manually create the device entries makes these device nodes
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persistent. Once created they will exist prior to the driver insmod.
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Attempting to connect an application to /dev/hvcs* prior to insertion of
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the hvcs module will result in an error message similar to the following:
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"/dev/hvcs*: No such device".
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NOTE: Just because there is a device node present doesn't mean that there
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is a vty-server device configured for that node.
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---------------------------------------------------------------------------
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5. Connection
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Since this driver controls devices that provide a tty interface a user can
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interact with the device node entries using any standard tty-interactive
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method (e.g. "cat", "dd", "echo"). The intent of this driver however, is
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to provide real time console interaction with a Linux partition's console,
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which requires the use of applications that provide bi-directional,
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interactive I/O with a tty device.
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Applications (e.g. "minicom" and "screen") that act as terminal emulators
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or perform terminal type control sequence conversion on the data being
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passed through them are NOT acceptable for providing interactive console
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I/O. These programs often emulate antiquated terminal types (vt100 and
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ANSI) and expect inbound data to take the form of one of these supported
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terminal types but they either do not convert, or do not _adequately_
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convert, outbound data into the terminal type of the terminal which invoked
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them (though screen makes an attempt and can apparently be configured with
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much termcap wrestling.)
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For this reason kermit and cu are two of the recommended applications for
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interacting with a Linux console via an hvcs device. These programs simply
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act as a conduit for data transfer to and from the tty device. They do not
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require inbound data to take the form of a particular terminal type, nor do
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they cook outbound data to a particular terminal type.
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In order to ensure proper functioning of console applications one must make
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sure that once connected to a /dev/hvcs console that the console's $TERM
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env variable is set to the exact terminal type of the terminal emulator
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used to launch the interactive I/O application. If one is using xterm and
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kermit to connect to /dev/hvcs0 when the console prompt becomes available
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one should "export TERM=xterm" on the console. This tells ncurses
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applications that are invoked from the console that they should output
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control sequences that xterm can understand.
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As a precautionary measure an hvcs user should always "exit" from their
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session before disconnecting an application such as kermit from the device
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node. If this is not done, the next user to connect to the console will
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continue using the previous user's logged in session which includes
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using the $TERM variable that the previous user supplied.
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Hotplug add and remove of vty-server adapters affects which /dev/hvcs* node
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is used to connect to each vty-server adapter. In order to determine which
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vty-server adapter is associated with which /dev/hvcs* node a special sysfs
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attribute has been added to each vty-server sysfs entry. This entry is
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called "index" and showing it reveals an integer that refers to the
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/dev/hvcs* entry to use to connect to that device. For instance cating the
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index attribute of vty-server adapter 30000004 shows the following.
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # cat index
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2
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This index of '2' means that in order to connect to vty-server adapter
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30000004 the user should interact with /dev/hvcs2.
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It should be noted that due to the system hotplug I/O capabilities of a
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system the /dev/hvcs* entry that interacts with a particular vty-server
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adapter is not guaranteed to remain the same across system reboots. Look
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in the Q & A section for more on this issue.
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---------------------------------------------------------------------------
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6. Disconnection
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As a security feature to prevent the delivery of stale data to an
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unintended target the Power5 system firmware disables the fetching of data
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and discards that data when a connection between a vty-server and a vty has
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been severed. As an example, when a vty-server is immediately disconnected
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from a vty following output of data to the vty the vty adapter may not have
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enough time between when it received the data interrupt and when the
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connection was severed to fetch the data from firmware before the fetch is
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disabled by firmware.
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When hvcs is being used to serve consoles this behavior is not a huge issue
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because the adapter stays connected for large amounts of time following
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almost all data writes. When hvcs is being used as a tty conduit to tunnel
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data between two partitions [see Q & A below] this is a huge problem
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because the standard Linux behavior when cat'ing or dd'ing data to a device
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is to open the tty, send the data, and then close the tty. If this driver
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manually terminated vty-server connections on tty close this would close
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the vty-server and vty connection before the target vty has had a chance to
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fetch the data.
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Additionally, disconnecting a vty-server and vty only on module removal or
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adapter removal is impractical because other vty-servers in other
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partitions may require the usage of the target vty at any time.
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Due to this behavioral restriction disconnection of vty-servers from the
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connected vty is a manual procedure using a write to a sysfs attribute
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outlined below, on the other hand the initial vty-server connection to a
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vty is established automatically by this driver. Manual vty-server
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connection is never required.
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In order to terminate the connection between a vty-server and vty the
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"vterm_state" sysfs attribute within each vty-server's sysfs entry is used.
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Reading this attribute reveals the current connection state of the
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vty-server adapter. A zero means that the vty-server is not connected to a
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vty. A one indicates that a connection is active.
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Writing a '0' (zero) to the vterm_state attribute will disconnect the VTERM
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connection between the vty-server and target vty ONLY if the vterm_state
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previously read '1'. The write directive is ignored if the vterm_state
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read '0' or if any value other than '0' was written to the vterm_state
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attribute. The following example will show the method used for verifying
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the vty-server connection status and disconnecting a vty-server connection.
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # cat vterm_state
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1
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # echo 0 > vterm_state
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # cat vterm_state
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0
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All vty-server connections are automatically terminated when the device is
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hotplug removed and when the module is removed.
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---------------------------------------------------------------------------
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7. Configuration
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Each vty-server has a sysfs entry in the /sys/devices/vio directory, which
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is symlinked in several other sysfs tree directories, notably under the
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hvcs driver entry, which looks like the following example:
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Pow5:/sys/bus/vio/drivers/hvcs # ls
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. .. 30000003 30000004 rescan
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By design, firmware notifies the hvcs driver of vty-server lifetimes and
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partner vty removals but not the addition of partner vtys. Since an HMC
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Super Admin can add partner info dynamically we have provided the hvcs
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driver sysfs directory with the "rescan" update attribute which will query
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firmware and update the partner info for all the vty-servers that this
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driver manages. Writing a '1' to the attribute triggers the update. An
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explicit example follows:
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Pow5:/sys/bus/vio/drivers/hvcs # echo 1 > rescan
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Reading the attribute will indicate a state of '1' or '0'. A one indicates
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that an update is in process. A zero indicates that an update has
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completed or was never executed.
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Vty-server entries in this directory are a 32 bit partition unique unit
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address that is created by firmware. An example vty-server sysfs entry
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looks like the following:
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # ls
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. current_vty devspec name partner_vtys
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.. index partner_clcs vterm_state
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Each entry is provided, by default with a "name" attribute. Reading the
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"name" attribute will reveal the device type as shown in the following
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example:
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Pow5:/sys/bus/vio/drivers/hvcs/30000003 # cat name
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vty-server
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Each entry is also provided, by default, with a "devspec" attribute which
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reveals the full device specification when read, as shown in the following
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example:
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # cat devspec
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/vdevice/vty-server@30000004
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Each vty-server sysfs dir is provided with two read-only attributes that
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provide lists of easily parsed partner vty data: "partner_vtys" and
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"partner_clcs".
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # cat partner_vtys
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30000000
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30000001
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30000002
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30000000
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30000000
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # cat partner_clcs
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U5112.428.103048A-V3-C0
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U5112.428.103048A-V3-C2
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U5112.428.103048A-V3-C3
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U5112.428.103048A-V4-C0
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U5112.428.103048A-V5-C0
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Reading partner_vtys returns a list of partner vtys. Vty unit address
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numbering is only per-partition-unique so entries will frequently repeat.
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Reading partner_clcs returns a list of "converged location codes" which are
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composed of a system serial number followed by "-V*", where the '*' is the
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target partition number, and "-C*", where the '*' is the slot of the
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adapter. The first vty partner corresponds to the first clc item, the
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second vty partner to the second clc item, etc.
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A vty-server can only be connected to a single vty at a time. The entry,
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"current_vty" prints the clc of the currently selected partner vty when
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read.
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The current_vty can be changed by writing a valid partner clc to the entry
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as in the following example:
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Pow5:/sys/bus/vio/drivers/hvcs/30000004 # echo U5112.428.10304
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8A-V4-C0 > current_vty
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Changing the current_vty when a vty-server is already connected to a vty
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does not affect the current connection. The change takes effect when the
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currently open connection is freed.
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Information on the "vterm_state" attribute was covered earlier on the
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chapter entitled "disconnection".
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---------------------------------------------------------------------------
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8. Questions & Answers:
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===========================================================================
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Q: What are the security concerns involving hvcs?
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A: There are three main security concerns:
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1. The creator of the /dev/hvcs* nodes has the ability to restrict
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the access of the device entries to certain users or groups. It
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may be best to create a special hvcs group privilege for providing
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access to system consoles.
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2. To provide network security when grabbing the console it is
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suggested that the user connect to the console hosting partition
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using a secure method, such as SSH or sit at a hardware console.
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3. Make sure to exit the user session when done with a console or
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the next vty-server connection (which may be from another
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partition) will experience the previously logged in session.
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---------------------------------------------------------------------------
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Q: How do I multiplex a console that I grab through hvcs so that other
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people can see it:
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A: You can use "screen" to directly connect to the /dev/hvcs* device and
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setup a session on your machine with the console group privileges. As
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pointed out earlier by default screen doesn't provide the termcap settings
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for most terminal emulators to provide adequate character conversion from
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term type "screen" to others. This means that curses based programs may
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not display properly in screen sessions.
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---------------------------------------------------------------------------
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Q: Why are the colors all messed up?
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Q: Why are the control characters acting strange or not working?
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Q: Why is the console output all strange and unintelligible?
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A: Please see the preceding section on "Connection" for a discussion of how
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applications can affect the display of character control sequences.
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Additionally, just because you logged into the console using and xterm
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doesn't mean someone else didn't log into the console with the HMC console
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(vt320) before you and leave the session logged in. The best thing to do
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is to export TERM to the terminal type of your terminal emulator when you
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get the console. Additionally make sure to "exit" the console before you
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disconnect from the console. This will ensure that the next user gets
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their own TERM type set when they login.
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---------------------------------------------------------------------------
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Q: When I try to CONNECT kermit to an hvcs device I get:
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"Sorry, can't open connection: /dev/hvcs*"What is happening?
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A: Some other Power5 console mechanism has a connection to the vty and
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isn't giving it up. You can try to force disconnect the consoles from the
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HMC by right clicking on the partition and then selecting "close terminal".
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Otherwise you have to hunt down the people who have console authority. It
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is possible that you already have the console open using another kermit
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session and just forgot about it. Please review the console options for
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Power5 systems to determine the many ways a system console can be held.
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OR
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A: Another user may not have a connectivity method currently attached to a
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/dev/hvcs device but the vterm_state may reveal that they still have the
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vty-server connection established. They need to free this using the method
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outlined in the section on "Disconnection" in order for others to connect
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to the target vty.
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OR
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A: The user profile you are using to execute kermit probably doesn't have
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permissions to use the /dev/hvcs* device.
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OR
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A: You probably haven't inserted the hvcs.ko module yet but the /dev/hvcs*
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entry still exists (on systems without udev).
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OR
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A: There is not a corresponding vty-server device that maps to an existing
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/dev/hvcs* entry.
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---------------------------------------------------------------------------
|
|
Q: When I try to CONNECT kermit to an hvcs device I get:
|
|
"Sorry, write access to UUCP lockfile directory denied."
|
|
|
|
A: The /dev/hvcs* entry you have specified doesn't exist where you said it
|
|
does? Maybe you haven't inserted the module (on systems with udev).
|
|
|
|
---------------------------------------------------------------------------
|
|
Q: If I already have one Linux partition installed can I use hvcs on said
|
|
partition to provide the console for the install of a second Linux
|
|
partition?
|
|
|
|
A: Yes granted that your are connected to the /dev/hvcs* device using
|
|
kermit or cu or some other program that doesn't provide terminal emulation.
|
|
|
|
---------------------------------------------------------------------------
|
|
Q: Can I connect to more than one partition's console at a time using this
|
|
driver?
|
|
|
|
A: Yes. Of course this means that there must be more than one vty-server
|
|
configured for this partition and each must point to a disconnected vty.
|
|
|
|
---------------------------------------------------------------------------
|
|
Q: Does the hvcs driver support dynamic (hotplug) addition of devices?
|
|
|
|
A: Yes, if you have dlpar and hotplug enabled for your system and it has
|
|
been built into the kernel the hvcs drivers is configured to dynamically
|
|
handle additions of new devices and removals of unused devices.
|
|
|
|
---------------------------------------------------------------------------
|
|
Q: For some reason /dev/hvcs* doesn't map to the same vty-server adapter
|
|
after a reboot. What happened?
|
|
|
|
A: Assignment of vty-server adapters to /dev/hvcs* entries is always done
|
|
in the order that the adapters are exposed. Due to hotplug capabilities of
|
|
this driver assignment of hotplug added vty-servers may be in a different
|
|
order than how they would be exposed on module load. Rebooting or
|
|
reloading the module after dynamic addition may result in the /dev/hvcs*
|
|
and vty-server coupling changing if a vty-server adapter was added in a
|
|
slot inbetween two other vty-server adapters. Refer to the section above
|
|
on how to determine which vty-server goes with which /dev/hvcs* node.
|
|
Hint; look at the sysfs "index" attribute for the vty-server.
|
|
|
|
---------------------------------------------------------------------------
|
|
Q: Can I use /dev/hvcs* as a conduit to another partition and use a tty
|
|
device on that partition as the other end of the pipe?
|
|
|
|
A: Yes, on Power5 platforms the hvc_console driver provides a tty interface
|
|
for extra /dev/hvc* devices (where /dev/hvc0 is most likely the console).
|
|
In order to get a tty conduit working between the two partitions the HMC
|
|
Super Admin must create an additional "serial server" for the target
|
|
partition with the HMC gui which will show up as /dev/hvc* when the target
|
|
partition is rebooted.
|
|
|
|
The HMC Super Admin then creates an additional "serial client" for the
|
|
current partition and points this at the target partition's newly created
|
|
"serial server" adapter (remember the slot). This shows up as an
|
|
additional /dev/hvcs* device.
|
|
|
|
Now a program on the target system can be configured to read or write to
|
|
/dev/hvc* and another program on the current partition can be configured to
|
|
read or write to /dev/hvcs*. Now you have a tty conduit between two
|
|
partitions.
|
|
|
|
---------------------------------------------------------------------------
|
|
9. Reporting Bugs:
|
|
|
|
The proper channel for reporting bugs is either through the Linux OS
|
|
distribution company that provided your OS or by posting issues to the
|
|
PowerPC development mailing list at:
|
|
|
|
linuxppc-dev@ozlabs.org
|
|
|
|
This request is to provide a documented and searchable public exchange
|
|
of the problems and solutions surrounding this driver for the benefit of
|
|
all users.
|