How to Use the Command 'lvs' (with Examples)

The lvs command is part of the Logical Volume Manager (LVM) system in Linux, which is used to display information about logical volumes. Logical volumes offer a more flexible and efficient way to manage disk space on a system, as compared to traditional partitions. The lvs command provides various options to gather detailed information about these volumes, helping system administrators effectively manage storage. Below, we explore several use cases of the lvs command to understand its utility and detailed functionalities.

Use Case 1: Display Information About Logical Volumes

Code:

lvs

Motivation:

Executing the lvs command without any additional options provides a quick overview of the logical volumes present on a system. This basic listing is often sufficient for administrators who need to get a general sense of the logical volume configuration at a glance.

Explanation:

• lvs: The base command, lvs, lists the logical volumes present within the current volume groups, displaying key details such as the volume name, size, and other important attributes.

Example Output:

  LV       VG      Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv_root  vg_name -wi-ao---- 50.00g
  lv_swap  vg_name -wi-ao---- 10.00g

Use Case 2: Display All Logical Volumes

Code:

lvs -a

Motivation:

The -a option is particularly useful for revealing all logical volumes, including those that may not be actively in use or are hidden. This comprehensive overview helps in ensuring that no logical volumes are overlooked during system audits or maintenance tasks.

Explanation:

• -a: This option stands for “all,” instructing the lvs command to include every logical volume, even those that are inactive or hidden from the standard view.

Example Output:

  LV       VG      Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv_root  vg_name -wi-ao---- 50.00g
  lv_swap  vg_name -wi-ao---- 10.00g
  [thinVol] vg_name twi-a-tz-- 100.00g

Use Case 3: Change Default Display to Show More Details

Code:

lvs -v

Motivation:

The -v option is for administrators who require an extended view of details beyond the default information. This verbose mode is instrumental in troubleshooting or when conducting in-depth analyses of logical volumes.

Explanation:

• -v: The verbose flag provides a more detailed output of the logical volumes, often including additional metadata and properties that are not displayed in the default view.

Example Output:

  LV       VG      Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv_root  vg_name -wi-ao---- 50.00g
  lv_swap  vg_name -wi-ao---- 10.00g
  Details: This might include more attributes and administrative metadata.

Use Case 4: Display Only Specific Fields

Code:

lvs -o lv_name,vg_name

Motivation:

This use case lets administrators tailor the command output to show only specific fields of interest. This is useful when generating reports or integrating with scripts that process certain data points from logical volumes.

Explanation:

• -o: This option specifies which output fields to display.
• lv_name,vg_name: These are field names selected by the user, representing logical volume name and volume group name, respectively.

Example Output:

  LV       VG     
  lv_root  vg_name
  lv_swap  vg_name

Use Case 5: Append Field to Default Display

Code:

lvs -o +lv_attr

Motivation:

Appending additional fields to the default output allows for quick customization without losing the standard set of data. This is particularly useful when administrators need to correlate standard data with one or more additional attributes.

Explanation:

• -o: As before, this specifies the output fields.
• +lv_attr: The + indicates that the specified field should be added to the default display, rather than replacing existing fields.

Example Output:

  LV       VG      Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv_root  vg_name -wi-ao---- 50.00g  wi-a-m----
  lv_swap  vg_name -wi-ao---- 10.00g  wi-a-m----

Use Case 6: Suppress Heading Line

Code:

lvs --noheadings

Motivation:

Suppressing the headings in output can make the information more suitable for machine processing, such as when piping the output into parsing scripts or when focusing purely on data rather than labels.

Explanation:

• --noheadings: This option removes the header line with field descriptions from the command output, providing a cleaner view for parsing.

Example Output:

lv_root  vg_name -wi-ao---- 50.00g 
lv_swap  vg_name -wi-ao---- 10.00g

Use Case 7: Use a Separator to Separate Fields

Code:

lvs --separator =

Motivation:

Changing the field separator is particularly useful in scripting or data analysis workflows where different delimiters are required. By using a custom separator, administrators can integrate seamlessly with tools or processes that require specific formats.

Explanation:

• --separator =: This option sets the field separator within the output to the specified character or string, here =, to suit specific data processing needs.

Example Output:

LV=VG=Attr=LSize=Pool=Origin=Data%=Meta%=Move=Log=Cpy%Sync=Convert
lv_root=vg_name=-wi-ao----=50.00g
lv_swap=vg_name=-wi-ao----=10.00g

Conclusion:

The lvs command, with its flexible options and detailed output capabilities, is a quintessential tool in any Linux administrator’s toolkit. By leveraging its many features, users can efficiently manage and analyze logical volumes, ensuring systems remain stable and optimized for performance. Each use case presented here highlights a different aspect of the command, elucidating its versatility and practicality in real-world scenarios.