Tuesday, 23 April 2013

Get to know the VIOS CLI

Get to know the VIOS CLI

VIOS commands are easy to learn and easy to remember
Why the VIOS is critical
IBM Power Systems™ are usually configured to use one or more VIOS. The VIOS allows you to share physical resources between logical partitions (LPARs). The VIOS is a critical component of your virtualized infrastructure, so it needs to remain stable. To protect the VIOS, there is a restricted Korn shell with a limited set of commands. Although root access is available, you can do most of the configuration and management using the restricted shell by logging in as the primary administrator, padmin.
VIOS commands use flags that almost explain themselves, making the commands quick to learn and easy to remember.

Logging on as padmin
To log on to the VIOS, you can connect via a console session or use Secure Shell (SSH) to log on via the network.
Console session
To use a console session, log on to the Hardware Management Console (HMC), Integrated Virtualization Manager (IVM), or Systems Director Management Console (SDMC); select the Virtual I/O Server logical partition; choose the option to open a terminal window or console session.
If your VIOS has network connectivity, you can get to a login prompt by using an SSH client such as PuTTY (see Resources).
Log in as the padmin user, as shown below in Listing 1.

Listing 1. Logging on as padmin

IBM Virtual I/O Server
login: padmin
padmin's Password:
Last unsuccessful login: Thu Jul  7 12:06:28 GMT+10:00 2011 on /dev/vty0
Last login: Fri Sep 16 05:51:47 GMT+10:00 2011 on ssh from nim1

The restricted shell
When you're logged on as padmin, you have access to the restricted Korn shell. From within that shell you can run the native VIOS commands, but it's not the same as having root access on AIX. In the restricted shell, you can't do the following:
  • Change directory.
  • Set variables for SHELL, ENV, or PATH.
  • Run a command with a path name that contains a forward slash (/).
  • Redirect command output using: >>|<> or >>. But you can use the pipe (|) and the tee command to capture command output.
Access to the unrestricted AIX shell
The VIOS's underlying operating system is AIX. You can get to the full (unrestricted) AIX shell by logging in to the restricted shell as padmin and then entering the oem_setup_env command. This gives you full root access to the AIX operating system, which runs the VIOS. However, use this with caution. The VIOS is critical to your environment and damage done here can have repercussions on all LPARs. You can't log in directly to the VIOS as root.
The exit command returns you to the restricted shell as padmin.

VIOS and AIX commands: Similarities and differences
Many of the commands in the VIOS shell are similar to AIX commands, but there are some important differences. If you know AIX—even a little—within a short time you should feel at home with the VIOS command line. When you understand the general patterns in the naming of VIOS commands and their flags, it's a short step to mastering them.

New terms for Power Systems users in IBM Systems Director

IBM Systems Director introduces some terms that might be new to Power Systems users. The termspartition and logical partition are being replaced by the term virtual server. The VIOS is now the utility virtual server. See Resources for more details.
Although the VIOS commands are often based on equivalent AIX commands, the flags for the VIOS CLI (when you're logged in aspadmin) usually have different flags from AIX. There are also some entirely new commands that are specific to the VIOS.
If you're familiar with using the AIX command line, when you first start using the VIOS command line you might find the differences a little daunting. So where do you go for help?
When you're logged into the VIOS command line as padmin, you can list the available commands by entering the helpcommand.
Because it's a Virtual I/O Server, many of the commands you need on the VIOS are related to devices and I/O. There are also install commands that give you the ability to update the VIOS. There are commands for managing users and security, as well as commands that help you manage volume groups, physical and logical volumes, and storage pools.
There are many standard utilities available, such as the vi editor, topasmorecrontabls, and others.
If you want to look at a command in more detail, you can get the command usage information by entering help followed by the command name. Listing 2 below provides an example with the lsvg command.

Listing 2. Help for the lsvg command

help lsvg

Usage: lsvg [-map | -lv | -pv] VolumeGroup ... [-field FieldName ...]
            [-fmt delimiter]

       Displays information about volume groups.

       -map    Displays information about the mapping of logical and
               physical volumes in the volume group.

       -field  Specifies a list of fields to be displayed.

       -fmt    Divides output by a user-specified delimiter.

       -lv     Displays information about logical volumes in the
               volume group.

       -pv     Displays information about physical volumes in the
               volume group.

For an even more detailed description of the command and its flags, use the man pages (for example, man lsvg).
It's not possible to go through each command in detail in this article. However, when you understand some of the common VIOS commands and flags, you have the key to learning the rest of the commands you need.

VIOS command patterns

CLI under the covers

If you need to see the debug output of a command that you're running as padmin, you can turn on debugging using export CLI_DEBUG=33. This shows you the underlying AIX commands that the padmin restricted shell is calling.
For more information about debugging the commands you are running on the VIOS CLI, see Resources.
For many VIOS commands, you can tell what they're for just by looking at the name. The prefix to the command is usually a clue about what it does. Commands starting with ls list or show information, such as device names, attributes, or Logical Volume Management (LVM) components. Commands to change existing devices usually start with ch. Commands for removing components generally start with rm, such as rmvdev and rmpath.
Here are some examples that show how VIOS commands follow these general patterns.
Commands to display or list information: ls
To list the mapping between physical, logical, and virtual devices, use the lsmap command. It's common to use lsmap -alland sift through the output one screen at a time, but you can specify a particular virtual Small Computer System Interface (vSCSI) adapter using the -vadapter flag, as you can see below in Listing 3.

Listing 3. An lsmap command example

lsmap -vadapter vhost6

 SVSA            Physloc                                      Client Partition ID
--------------- -------------------------------------------- ------------------
vhost6          U9117.MMA.SN12A345B-V1-C110                    0x0000000a

VTD                   sapcrm_boot_a
Status                Available
LUN                   0x8100000000000000
Backing device        hdisk64
Physloc               U789D.001.DQD72TP-P1-C1-T1-W500507680110239F-L3E000000000000
Mirrored              false

The -dev flag is used to name the device, and it's the usual flag used for VIOS commands that identify a device. So, to list a device you can use lsdev followed by -dev and the device name, as shown in Listing 4.

Listing 4. List a device with lsdev

lsdev -dev hdisk65
name             status      description
hdisk65          Available   MPIO IBM 2145 FC Disk

To list all device attributes, add the -attr flag. If you specify a single attribute, its current value is shown. Listing 5 below shows how to see the reserve policy of a disk.

Listing 5. List attributes of a device

lsdev -dev hdisk65 -attr reserve_policy

There are many AIX LVM commands, such as lsvg to list volume groups and their characteristics and lspv to list physical volumes. However, the flags for these commands are not the same as in AIX. Use lsvg -lv VGName to list the logical volumes in a volume group. To see which physical volumes belong to a volume group, use lsvg -pv VGName.
Commands to make a new device: mk
Commands that add or make something generally start with mk. For example, Listing 6 shows the command to create a file-backed virtual optical device.

Listing 6. Make a file-backed optical device

mkvdev -vadapter vhost6 -fbo -dev crm_cd0
crm_cd0 Available

You can use this device to load an image in ISO format using the virtual media repository. To create the repository, use mkrep. See Resources for more information on how to make use of virtual optical devices.
Commands to change attributes and settings: ch
If you want to change attributes, the command is chdev. Listing 7 shows how to set the queue depth on a disk.

Listing 7. Change a device attribute

chdev -dev hdisk65 -attr queue_depth=20
hdisk65 changed

If the device is in use, you may need to change the characteristics permanently in the device's database without actually changing the current settings. To do that, add the -perm flag. This is similar to the -P flag for the AIX chdev command.
There are a number of commands that make changes to devices. To change the device status of an MPIO-capable device, you can use chpath. To change an optical disk in the virtual media repository, for example to set it to read-only access so it can be loaded onto multiple virtual optical devices, use chvopt.
Commands to remove or delete: rm
If you haven't already guessed, you can delete or remove using the rm commands. To remove a virtual target device, use rmvdev. You can remove an MPIO path using rmpath. You can take an ISO image out of the virtual media repository using rmvopt.

Common flags
Although commands are the same as AIX, or at least similar, the flags are different. VIOS commands typically use longer, more descriptive flags rather than a single character as AIX tends to do. For example, -dev is used for devices, -attr for attributes, and -fmt to specify the format of the output.
Longer flags may make for a little more typing than you usually find in AIX, but they also make the commands more obvious and easy to remember. For example, if you need a flag to indicate a logical volume, use -lv. In the same way, you can refer to physical volumes with the -pv flag. Table 1 below shows some sample flags used by the VIOS restricted shell.

Table 1. Some VIOS command flags
-lvLogical volumelsvg -lv rootvg
-pvPhysical volumelsvg -pv rootvg
-dev NameDevicermdev -dev cd0
-attr Attribute=ValueAttributechdev -dev hdisk0 -attr reserve_policy=no_reserve
-permPermanent changechdev -dev hdisk0 -attr reserve_policy=no_reserve -perm
When you know the types of flags that VIOS commands expect, you can more easily remember commands without having to look up the syntax.

UNIX commands
There are also several standard UNIX® shell commands that you can use from within the restricted shell, such as lsrmcp,dategreptailchmodvimoreteeftp, and several others.
As you can see, if you know your way around the AIX command line, the VIOS has a welcome mat out for you.

In this article you saw how you can learn to use the VIOS CLI. If you know AIX commands, it's an advantage to learning similar VIOS commands. And if you're making the transition from VIOS to AIX, your experience logged into the VIOS as padmin is a great stepping stone for the AIX CLI.

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