Audit LVM Volume Groups with vgs

You will finish with a repeatable way to inspect LVM volume groups, choose the columns that matter, and hand the result to a shell script or monitoring check. The examples use the LVM tools 2.03.16(2) installed with this guide. Allow about 10 minutes for a first audit, plus time to investigate any missing groups.

Before you start

You need the vgs command from the lvm2 package. Reading metadata is normally a privileged administration task, so run the commands as root or through sudo when your host requires it. Nothing in this guide changes LVM metadata, but a restricted user may see warnings or an incomplete report.

Start by recording the installed version. This matters because report fields and defaults can differ between LVM releases.

vgs --version

On this machine the relevant lines are:

LVM version:     2.03.16(2) (2022-05-18)
Library version: 1.02.185 (2022-05-18)

Checkpoint: get the normal inventory

Run vgs with no volume-group argument to list the groups visible to LVM. The usual report includes the group name, physical-volume count, logical-volume count, size, and free space. The command is a report, not a create, extend, or remove operation.

sudo vgs

To request one known group, put its name after the options:

sudo vgs vg_data

A name can also be a tag. If a group appears to be absent, do not immediately edit configuration or scan random devices. Visibility may be restricted by the device filter, a devices file, locking, or the group being foreign to this host. Check the warnings first.

Choose stable columns

The default display is convenient for a person but awkward for scripts. Use --options with a comma-separated list. These fields are a useful capacity audit:

sudo vgs --options vg_name,vg_uuid,vg_size,vg_free,pv_count,lv_count

The field order is the order you request. Ask the installed command for the complete field list rather than assuming a field from a different release:

vgs --options help

Use --noheadings when another program will consume the rows, and --separator to make the boundary explicit.

sudo vgs --noheadings --separator '|' \
  --options vg_name,vg_size,vg_free,pv_count,lv_count

Expected output on a host with a group resembles this shape. Values and spacing depend on the host, so treat it as a format example, not a promised inventory:

vg_data|<size>|<free>|<pv-count>|<lv-count>

For machine parsing, also consider JSON. The report format is controlled globally by LVM configuration, so specify it when a consumer depends on it.

sudo vgs --reportformat json --options vg_name,vg_size,vg_free

Make sizes unambiguous

Human-readable sizes are useful at a terminal, but suffixes and binary units can surprise arithmetic. Select a unit explicitly. Lowercase units use powers of 1024; uppercase units use SI multiples of 1000. Bytes are a straightforward choice for a parser.

sudo vgs --units b --nosuffix \
  --noheadings --separator '|' \
  --options vg_name,vg_size,vg_free

--nosuffix only makes sense with a chosen unit, apart from the human-readable modes. Without it, values can include a unit suffix. The r human-readable mode can add a less-than sign to indicate rounding; use h when you want human-readable output without that rounding indicator.

Filter and sort the report

Use --select for report-side filtering. Its expression language is specific to LVM, so inspect the fields and selection help on the installed version before building a larger expression.

vgs --select help
vgs --options help

A simple example asks for groups with free space below a chosen threshold. The exact comparison and size syntax should be tested against the fields available on your host before putting it in an alert:

sudo vgs --select 'vg_free < 10g' \
  --options vg_name,vg_size,vg_free

Sort explicitly when output is compared over time. Prefix a column with a minus sign for reverse order.

sudo vgs --sort -vg_free --options vg_name,vg_free

Checkpoint: investigate missing groups safely

First compare the default inventory with all groups:

sudo vgs --all

The manpage defines --all as equivalent to omitting a group argument. It does not bypass every visibility rule. --foreign includes volume groups that LVM would otherwise skip because their system identity belongs elsewhere. Use it for inspection, not as a reason to activate or modify a foreign group.

sudo vgs --foreign --options vg_name,vg_systemid,vg_size,vg_free

If your installation uses the LVM devices file, --devicesfile NAME selects a file under /etc/lvm/devices/, and --devices /dev/DEVICE restricts the devices visible to the command. A restricted device list can make a healthy group look incomplete or missing. Confirm the intended devices before diagnosing metadata damage.

For a read-only inspection of on-disk metadata, --readonly avoids taking locks and does not communicate with the device-mapper kernel driver. That makes it useful for examining metadata associated with an image while a virtual machine is running, but it cannot tell you whether logical volumes are currently in use.

sudo vgs --readonly --reportformat json \
  --options vg_name,vg_uuid,vg_size,vg_free

Warnings and unsafe shortcuts

Do not add --nolocking to make a warning disappear. The manual warns that concurrent commands can then produce incorrect results. Likewise, --ignorelockingfailure permits some read-only metadata operations after a locking failure, but it is not a repair and should not hide a cluster or shared-storage problem.

The --shared option reports shared groups that would otherwise be skipped when lvmlockd is not being used. Use it only when you understand the host's shared-volume arrangement. --foreign, --shared, device restrictions, and read-only mode change what the report means; record the options with any exported result.

Although vgs is a reporting command, common LVM options include --yes and --test. Do not copy those options into a generic command template. --yes suppresses confirmation prompts and is hazardous when reused with a different LVM command. --test disables metadata writing, but the manual warns that multi-stage tools can still produce unusual messages. Neither option repairs a failed report.

Done means

• vgs --version is recorded with the audit.
• The normal report and, where needed, --all or --foreign have been compared.
• Script output names its fields, uses an explicit separator or JSON, and specifies units when arithmetic is involved.
• Any device-file, locking, shared-group, or foreign-group warning has been investigated before changing LVM configuration.
• No report command was confused with an activation, repair, resize, or removal operation.