Specifying a Disk Group to Commands

Note Most VxVM commands require superuser or equivalent privileges.

Many VxVM commands allow you to specify a disk group using the -g option. For example, the following command creates a volume in the disk group, mktdg:

# vxassist -g mktdg make mktvol 5g

The block special device corresponding to this volume is:

/dev/vx/dsk/mktdg/mktvol

System-Wide Reserved Disk Groups

The following disk group names are reserved, and cannot be used to name any disk groups that you create:

bootdg Specifes the boot disk group. This is an alias for the disk group that contains the volumes that are used to boot the system. VxVM sets bootdg to the appropriate disk group if it takes control of the root disk. Otherwise, bootdg is set to nodg (no disk group; see below).

Caution Do not attempt to change the assigned value of bootdg. Doing so may render your system unbootable.

defaultdg Specifies the default disk group. This is an alias for the disk group name that should be assumed if the -g option is not specified to a command, or if the VXVM_DEFAULTDG environment variable is undefined. By default, defaultdg is set to nodg (no disk group; see below).

nodg Specifies to an operation that no disk group has been defined. For example, if the root disk is not under VxVM control, bootdg is set to nodg.

Note If you have upgraded your system, you may find it convenient to continue to configure a disk group named rootdg as the default disk group (defaultdg). There is no requirement that both defaultdg and bootdg refer to the same disk group, nor that either the default disk group or the boot disk group be named rootdg.

Rules for Determining the Default Disk Group

It is recommended that you use the -g option to specify a disk group to VxVM commands that accept this option. If you do not specify the disk group, VxVM applies the following rules in order until it determines a disk group name:

Use the default disk group name that is specified by the environment variable VXVM_DEFAULTDG. This variable can also be set to one of the reserved system-wide disk group names: bootdg, defaultdg, or nodg. If the variable is undefined, the following rule is applied.
Use the disk group that has been assigned to the system-wide default disk group alias, defaultdg. See Displaying and Specifying the System-Wide Default Disk Group. If this alias is undefined, the following rule is applied.
If the operation can be performed without requiring a disk group name (for example, an edit operation on disk access records), do so.

If none of these rules succeeds, the requested operation fails.

Caution In releases of VxVM prior to 4.0, a subset of commands attempted to deduce the disk group by searching for the object name that was being operated upon by a command. This functionality is no longer supported. Scripts that rely on deducing the disk group from an object name may fail.

Displaying the System-Wide Boot Disk Group

To display the currently defined system-wide boot disk group, use the following command:

# vxdg bootdg

See the vxdg(1M) manual page for more information.

Displaying and Specifying the System-Wide Default Disk Group

To display the currently defined system-wide default disk group, use the following command:

# vxdg defaultdg

If a default disk group has not been defined, nodg is displayed. Alternatively, you can use the following command to display the default disk group:

# vxprint -Gng defaultdg 2>/dev/null

In this case, if there is no default disk group, nothing is displayed.

Use the following command to specify the name of the disk group that is aliased by defaultdg:

# vxdctl defaultdg diskgroup

If bootdg is specified as the argument to this command, the default disk group is set to be the same as the currently defined system-wide boot disk group.

If nodg is specified as the argument to the vxdctl defaultdg command, the default disk group is undefined.

Note The specified diskgroup need not currently exist on the system.

See the vxdctl(1M) and vxdg(1M) manual pages for more information.


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Product: Volume Manager Guides
Manual: Volume Manager 4.1 Administrator's Guide
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