vgscan(1M)

NAME

vgscan — scan physical volumes for LVM volume groups

SYNOPSIS

/usr/sbin/vgscan [-a] [-p] [-v]

DESCRIPTION

The vgscan command allows the re-creation of the /etc/lvmtab file and possibly the associated volume group device files. This command should be run only in the event of a catastrophic error such as the deletion of the /etc/lvmtab file or the mismatch of names of the physical volumes in the /etc/lvmtab file to the actual physical volume path configuration. If the /etc/lvmtab file exists, the information contained in the file is used to assist in rebuilding the file, but the existing file is updated with the new corrected configuration.

vgscan searches each physical volume connected to the system, looking for logical volumes. If there are dual controller devices, only the primary controller device path is scanned, unless you specify the -a option to allow access to all paths. It groups these physical volumes into volume groups by matching the volume group information found on the physical volumes. Then it searches the /dev directory for all group device files with the LVM major number, and tries to match device files with the logical volumes' information found on the physical volumes.

If matches occur, it determines the volume group name from the device file path, and updates the /etc/lvmtab file with the volume group name and the list of physical volumes paths contained in that volume group. For volume groups where the device files cannot be matched, it prints the list of physical volumes for each volume group.

After vgscan completes successfully, run the vgimport command on each set of unmatched physical volumes (see vgimport(1M)).

Options

vgscan recognizes the following options:

-a: Scan all controller device paths for all disks.
-p: Preview the actions that would be taken but do not update file /etc/lvmtab. This option is best used in conjunction with the -v option.
-v: Print verbose messages.

WARNINGS

The following warning only applies to dual controller devices (NIKE), or disks with alternate path:

Since vgscan search each disks on the system in the order of where they have configured. When vgscan reconstructs the /etc/lvmtab file, the order of disks in the file could be different than it was before. The following will happen:

The designated primary and alternate link might not be the same as it was configured before.
Alternate links will be added to the /etc/lvmtab file even if they might not be configured in the volume group initially.
The boot information might be incorrect due to different order of disks in the new /etc/lvmtab file.

In order to correct the above problems, do the following:

Use vgchange with -a option to activate all volume groups.
Use lvlnboot with -R option to correct boot information on disk.
Use vgreduce to reduce any alternate links that were added to the /etc/lvmtab file by vgscan, but they were not needed.
If the original primary path of a disks become an alternate path after /etc/lvmtab file is reconstructed, the order can be easily reverted by using vgreduce to remove the primary path and use vgextend to add the path back again.

If /etc/lvmtab is destroyed, do not use vgscan to re-construct /etc/lvmtab if the system is heavily loaded by an application. Otherwise, vgscan will create an incomplete /etc/lvmtab due to a known NIKE/LVM limitation issue. It's important to quiesce the logical volume's I/O before re-constructing the /etc/lvmtab.

If for some reason, there is a need to re-construct /etc/lvmtab when the system is running production application, vgscan will create a partial /etc/lvmtab. In this case, most of the primary paths should be included in the /etc/lvmtab. Use vgextend to include any missing alternate paths in the VG.

EMC DISK WARNINGS

Starting at 10.20, the vgscan command is supporting additional EMC Symmetrix disk product functionality (see vgchgid(1M)). The vgscan command will be enforcing a new rule such that only EMC disks with the same attributes can belong to the same volume group. Note that an EMC disk, without any of the additional attributes, can still be mixed with non-EMC disks in the same volume group. Please consult your EMC Symmetrix documentation, if applicable.

EXTERNAL INFLUENCES

Environment Variables

LANG determines the language in which messages are displayed.

If LANG is not specified or is null, it defaults to "C" (see lang(5)).

If any internationalization variable contains an invalid setting, all internationalization variables default to "C" (see environ(5)).

EXAMPLES

Scan the primary controller device paths for all the physical volumes on the system, but do not update the /etc/lvmtab file:

vgscan -p -v 

Scan all controller device paths to all physical volumes on the system:

vgscan -a -v 

Scan the primary controller device paths for all the physical volumes on the system and re-create /etc/lvmtab file:

vgscan -v 

The following messages will appear after /etc/lvmtab file is re-created.

*** LVMTAB has been created successfully.
*** If PV links are configured in the system
*** Do the following to resync information on disk.
*** #1. vgchange -a y
*** #2. lvlnboot -R