Linux RHCSA Part 19 - File Systems - Additional useful commands

From time to time, you need to perform file system maintenance and clean things up a bit to ensure everything runs efficiently and without issues. Usually, during maintenance, the file system in question is taken offline, i.e., unmounted. Something along the lines of a boss's order: "We need to tidy up the file system on /dev/hdb1 this Wednesday." So, let's get to work. 

First, you need to locate the appropriate file system by the label assigned to it. Using labels makes finding the correct file system faster and easier. 

Step 2 - If the file system does not have a label, let's assign one 

# e2label /dev/hdb1 CData

Step 3 - Verify that the label has been assigned correctly 

In this example, we don't have many file systems, so finding the right one even without labels isn't a problem. However, if you were working in a much larger environment with specific file systems, you can use the "findfs" tool to help. 

findfs tool syntax: # findfs LABEL=<label> | UUID=<uuid>

Step 4 - Let's find a file system knowing its label. 

Once we verify that a given label points to a specific file system, we can learn more about it using the "blkid" command. 

blkid command syntax: # blkid [options] 

blkid command options: 

• -s       Displays tags
• dev    Specifies the device to examine

# mount LABEL=CData /opt/company_data

In a REDHAT environment, we used the "LABEL" switch with this command. If you wanted to perform the same action in an UBUNTU or DEBIAN environment, you could use the "-L" switch to achieve the same result. 

We can update the /etc/fstab file with additional entries related to file system labels. Do not unmount the file systems just yet - we have a few more things to do. Previously, we discussed creating and managing Logical Volumes (LVM) and the benefits of being able to extend partitions. If there is any free disk space in the system, we can use it, or if not, simply add a new disk to increase the available space. You don't get these benefits with basic partitions. To increase the size of a basic partition, you must destroy all current partitions, increase the size, and finally recreate the file system. Since /dev/hdd is configured as LVM, we will use it for the next exercise. We will use the "resize2fs" command to enlarge the file system. Before performing an extension, it is good practice to check the integrity of the file system beforehand using the "e2fsck" command.

e2fsck command syntax: # e2fsck [options] device

e2fsck command options:

• -p    - Automatic repair (no prompts)
• -n    - Do not make any changes to the file system
• -y    - Answer "yes" to all questions
• -f     - Force file system check
• -v    - Display verbose information