Mastering the 'vgs' Command in LVM Management (with examples)

The vgs command is an essential tool for managing Logical Volume Manager (LVM) setups on Linux systems. It provides an array of capabilities for displaying detailed information about volume groups, allowing system administrators to have a comprehensive overview of their storage configurations. This command is highly versatile, offering various options to tailor the output according to the user’s needs and preferences, thus aiding in efficient system monitoring and management.

Use case 1: Display information about volume groups

Code:

vgs

Motivation:

The primary and most common use of the vgs command is to display current information about all available volume groups on the system. This simple display helps administrators quickly assess the state and configuration of their storage setups, making it an invaluable tool for regular system audits and checks.

Explanation:

• vgs: This is the command itself, which, without any additional options, displays a summary of all volume groups configured on the system. It presents a concise overview, typically showing the volume group name, physical volume count, logical volume count, and other essential metrics.

Example output:

VG     #PV #LV #SN Attr   VSize   VFree
vg01     1   2   0 wz--n- <10.00g  <1.00g
vg02     2   3   0 wz--n- <20.00g <5.00g

Use case 2: Display all volume groups

Code:

vgs -a

Motivation:

The -a option is useful when administrators need to view details of all volume groups, including any that are inactive or inaccessible. This might be necessary during troubleshooting or when preparing to activate or deactivate certain volume groups.

Explanation:

• -a: This option stands for “all,” instructing vgs to include all volume groups in the output, regardless of their state.

Example output:

VG     #PV #LV #SN Attr   VSize   VFree
vg01     1   2   0 wz--n- <10.00g  <1.00g
vg02     2   3   0 wz--n- <20.00g <5.00g
vg03     0   0   0 d---n-  0       0

Use case 3: Change default display to show more details

Code:

vgs -v

Motivation:

Administrators may require a more detailed view of each volume group to gain insights into specific attributes, such as metadata, allocation units, or other intricate properties. The verbose option helps to delve deeper into the configurations, aiding in thorough analyses and informed decision-making.

Explanation:

• -v: The verbose option increases the amount of information displayed for each volume group, typically including further breakdown into component parts or additional statistics.

Example output:

    Finding all volume groups
    Checking for volume group vg01
VG     #PV #LV #SN Attr   VSize   VFree
vg01     1   2   0 wz--n- <10.00g  <1.00g
  vg01 0 0 0 
    Checking for volume group vg02
VG     #PV #LV #SN Attr   VSize   VFree
vg02     2   3   0 wz--n- <20.00g <5.00g

Use case 4: Display only specific fields

Code:

vgs -o vg_name,lv_count

Motivation:

Sometimes administrators are interested only in specific pieces of data and not the entire breadth of information that vgs provides by default. Selecting specific fields streamlines the output, making it easier to locate and analyze the desired data quickly.

Explanation:

• -o: This option allows the user to specify which fields to display, focusing only on the necessary information.
• vg_name: Specifies that only the name of the volume group should be displayed.
• lv_count: Specifies that the count of logical volumes within each volume group should be displayed.

Example output:

VG     #LV
vg01     2
vg02     3

Use case 5: Append field to default display

Code:

vgs -o +vg_uuid

Motivation:

There may be instances where the default information is sufficient, but supplementary data about each volume group, such as the UUID, is needed for precise identification. Appending fields provide this flexibility without cluttering the output excessively.

Explanation:

• -o: Similar to the previous example, this option dictates which fields are displayed.
• +vg_uuid: By prefixing the field with a plus sign, this indicates that the specified field (vg_uuid in this case) should be added to the default set of fields.

Example output:

VG     #PV #LV #SN Attr   VSize   VFree  VG UUID
vg01     1   2   0 wz--n- <10.00g  <1.00g NIFm42-Zbjs-0987-ABCD-1234
vg02     2   3   0 wz--n- <20.00g <5.00g  XEDg34-Acde-5678-XYZW-5678

Use case 6: Suppress heading line

Code:

vgs --noheadings

Motivation:

In certain automated scripts or data parsing operations, headings can complicate data processing. Suppressing the headings enables clean, raw data output that streamlines feeding the data into subsequent processing or monitoring tools.

Explanation:

• --noheadings: This option removes the column headings from the output, providing a pure data display.

Example output:

vg01     1   2   0 wz--n- <10.00g  <1.00g
vg02     2   3   0 wz--n- <20.00g <5.00g

Use case 7: Use separator to separate fields

Code:

vgs --separator = 

Motivation:

When incorporating output into spreadsheets or databases, using a specific delimiter can enhance data organization, ensuring that fields are correctly parsed and aligned. This is especially helpful in data export or interchange scenarios.

Explanation:

• --separator =: Customizes the delimiter used to separate each field in the output, switching from the default to an equals sign in this case, aligning with the format requirements of certain data processing tools.

Example output:

VG=vg01 #PV=1 #LV=2 #SN=0 Attr=wz--n- VSize=<10.00g VFree=<1.00g
VG=vg02 #PV=2 #LV=3 #SN=0 Attr=wz--n- VSize=<20.00g VFree=<5.00g

Conclusion:

The vgs command is a powerful tool for extracting a wealth of information on volume groups within an LVM setup. Whether a user needs a broad overview or detailed specifics, vgs offers an array of options to tailor the data display, optimizing both manual inspection and automated data parsing workflows. By mastering the various use cases, system administrators can leverage vgs to maintain and fine-tune their storage environments effectively.