UUIDs are a great way to label filesystems, especially in smaller environments. The UUID remains persistently assigned to the filesystem. Directly below the root filesystem, you find the Universally Unique Identifier (UUID). You may see any number of options here, such as ext3, ext4, fat file systems, etc. You also see that it is an xfs filesystem. The first (and only, in this case) filesystem that you see is the root filesystem for this VM /dev/mapper/rhel-root. Now that we have looked at the comments, let's break down the actual configuration that is present and look at the various bits of info that a user needs to note. Next, skip down to the After editing section and note the systemctl daemon-reload command used to update the systemd components after making changes to this file. These directories and man pages are worth noting and can provide valuable information should you need it. For now, ignore the Created by section and move to the Accessible filesystems portion. The first thing that pops out at you is the comments in the header. This table consists of six columns defining certain parameters around a given filesystem. dev/mapper/rhel-swap swap swap defaults 0 0 # After editing this file, run 'systemctl daemon-reload' to update systemd # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info. # Accessible filesystems, by reference, are maintained under '/dev/disk/'. # Created by anaconda on Mon Jan 27 10:04:34 2020 You will see my fstab below: ~]$ vi /etc/fstab Obviously your table will be different depending on your environment, however, I want to look at an example using a virtual machine so that we can see what information is provided and break down what we are seeing. The root filesystem should be set to 1 and other partitions set to 2. Numbers higher than this represent the check order. 0 means that fsck will not check the filesystem. File System Check Order: (second digit) Here we can see three possible outcomes.This is an outdated backup method and should NOT be used. Backup Operation: (the first digit) this is a binary system where 1 = dump utility backup of a partition.If using multiple options they must be separated by commas. Options: lists any active mount options.File System Type: nothing trick here, shows the type of filesystem in use.Mount Point: designates the directory where the device is/will be mounted.Device: usually the given name or UUID of the mounted device (sda1/sda2/etc).The columns of the table are as follows from left to right: The table itself is a 6 column structure, where each column designates a specific parameter and must be set up in the correct order. Not only is it less work over time, but it also allows the user to avoid load order errors that could eat up valuable time and energy. It is designed to configure a rule where specific file systems are detected, then automatically mounted in the user's desired order every time the system boots. The fstab file became an attractive option because of challenges like this. In the time of the ancients, users had to manually mount these drives to a file location using the mount command. Today, we are so used to the plug and play nature of our favorite external drives that we may completely forget that operations are going on behind the scenes to mount the drive and read/write data. It is a set of rules used to control how different filesystems are treated each time they are introduced to a system. Your Linux system's filesystem table, aka fstab, is a configuration table designed to ease the burden of mounting and unmounting file systems to a machine. These can be a bit tricky for a lot of users, so we will look at /etc/fstab ( fstab) a little closer. Filesystems, and by necessity, filesystem tables, are one of these constants. For all of the improvements made, there are still "old school" pieces of the puzzle that we simply can't live without. They have a smaller footprint, are more efficient with resource management, and have become much faster than early computing systems. Operating systems have come a long way in recent years. Linux system administration skills assessment.A guide to installing applications on Linux.Download RHEL 9 at no charge through the Red Hat Developer program.
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