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HP-UX System Administrator's Guide: Logical Volume Management: HP-UX 11i Version 3 > Chapter 4 Troubleshooting LVM

Troubleshooting Tools Overview


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This section describes the tools available for troubleshooting LVM problems.

Information Collection

You can collect information about your LVM configuration using the vgdisplay, lvdisplay, pvdisplay, and lvlnboot commands. As noted in “Planning for Recovery”, periodically collect the outputs from the commands listed in Table 4-1.

Table 4-1 LVM Information to Collect and Maintain


ioscan -f

Prints I/O configuration

lvlnboot -v

Prints information on root, boot, swap, and dump logical volumes.

vgcfgrestore -l

All volume groups

Prints volume group configuration from the backup file.

vgdisplay -v

All volume groups

Prints volume group information, including status of logical volumes and physical volumes.

lvdisplay -v

All logical volumes

Prints logical volume information, including mapping and status of logical extents.

pvdisplay -v

All physical volumes

Prints physical volume information, including status of physical extents.


In addition, use the lvmadm command for two purposes:

  • To determine which volume group versions are supported by your release of HP-UX 11i Version 3. For example, if your release supports Version 2.1 volume groups, lvmadm displays the following:

    # lvmadm -t -V 2.1 --- LVM Limits --- VG Version 2.1 Max VG Size (Tbytes) 2048 Max LV Size (Tbytes) 256 Max PV Size (Tbytes) 16 Max VGs 2048 Max LVs 2047 Max PVs 2048 Max Mirrors 5 Max Stripes 511 Max Stripe Size (Kbytes) 262144 Max LXs per LV 33554432 Max PXs per PV 16777216 Max Extent Size (Mbytes) 256

    If your release does not support Version 2.1 volume groups, it displays the following:

    # lvmadm -t -V 2.1 Error: 2.1 is an invalid volume group version.
  • To display the contents of the /etc/lvmtab and /etc/lvmtab_p files in a human-readable fashion. For example, the following command displays the contents of the LVM configuration files for all Version 1.0 volume groups on your system:

    # lvmadm -l -V 1.0 --- Version 1.0 volume groups --- VG Name /dev/vg00 PV Name /dev/disk/disk34_p2

In addition, there are some tools available from your HP support representative:

  • dump_lvmtab: prints the contents of the /etc/lvmtab file in human-readable fashion.

  • vgcfgdisplay: prints the contents of an LVM volume group configuration backup file (as created by vgcfgbackup), such as the volume group information, the logical volume information, physical volume information and logical extent distribution.

Consistency Checks

Most LVM commands perform consistency checking. You can inspect your LVM configuration with the vgdisplay, lvdisplay, and pvdisplay commands, and look for inconsistencies.

In addition, the pvck command performs explicit consistency checking on a physical volume. This command detects bad checksums caused by a forward system migration after a backward system migration. Run pvck only on deactivated volume groups. For more information, see pvck(1M).

NOTE: The pvck command does not support Version 2.x volume groups.

Maintenance Mode Boot

LVM maintenance mode boot is a special way to boot your system that bypasses the normal LVM structures. Use it only for problems that prevent the system from otherwise booting. It is similar to single-user state in that many of the processes that normally start do not start, and many of the system checks are not performed. LVM maintenance mode is intended to enable you to boot your system long enough to repair damage to the system LVM data structures typically using vgcfgrestore, which then enables you to boot your system normally.

Normally, the boot loader uses the LABEL file in the LIF volume to determine the location of the boot file system and the kernel /stand/vmunix. The LABEL file also contains the starting block and size of the root file system.

Under a maintenance mode boot, the boot loader attempts to find the boot file system at the start of the boot disk's user data area rather than using information from the LIF volume. To obtain the root file system's starting block and size, the boot loader reads the file /stand/rootconf. Since LVM is not enabled, the root file system must be allocated contiguously.

A maintenance mode boot differs from a standard boot as follows:

  • The system is booted in single-user mode.

  • No volume groups are activated.

  • Primary swap and dump are not available.

  • Only the root file system and boot file system are available.

  • If the root file system is mirrored, only one copy is used. Changes to the root file system are not propagated to the mirror copies, but those mirror copies are marked stale and will be synchronized when the system boots normally.

To boot in maintenance mode on a system with a root disk configured with LVM, use the -lm option to the boot loader. On an HP 9000 server, enter the following command:

ISL> hpux -lm

On an HP Integrity server, enter the following command:

HPUX> boot -lm
CAUTION: When you boot your system in maintenance mode, do not activate the root volume group and do not change to multiuser mode (for example, by specifying /sbin/init 2). Doing so can corrupt the root file system.

When you have repaired or restored the LVM configuration information, reboot the system using the following command:

# /sbin/reboot

For more information about LVM maintenance mode boots and troubleshooting problems with LVM structures, see Disk and File Management Tasks on HP-UX, published by Prentice Hall PTR, 1997.

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