File System Management: commands lsblk, blkid

1. The Importance of Understanding File Systems

Welcome to a new lecture in the course, where we're diving into the fascinating world of Linux file systems. Today we’ll learn how to find devices, understand their structure, and figure out what types of file systems are installed on them. We'll add a bit of command-line magic with tools like lsblk and blkid. Plus, we’ll talk about why programmatically controlled picks for "data digging" are always awesome!

What is a File System?

If the operating system is the "heart" of your computer, then the file system is its "nervous system." It's what organizes and manages access to data on storage devices (hard drives, SSDs, USB drives). It determines how data is stored, read, and written.

Examples of file systems you might encounter:

• ext4 — the standard file system for most Linux distributions.
• NTFS — the file system used by Windows.
• FAT32 — popular for external drives and flash drives.
• XFS, btrfs — more advanced Linux alternatives with features like snapshots.

When you plug in a disk or flash drive into Linux, its file system needs to be "mounted" so the system can start working with it. We’ll manage this (and much more) using commands.

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2. The lsblk Command: Overview of Connected Devices

Basics of the lsblk Command

Linux has tons of tools for working with devices and partitions. One of the most useful ones is the lsblk command. Its name stands for "list block devices" — showing a list of block devices.

Simple syntax:

lsblk

This command outputs a table of all block devices in the system, including hard drives, SSDs, USB drives, and their partitions.

Example output:

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  500G  0 disk 
├─sda1   8:1    0   50G  0 part /
├─sda2   8:2    0  200G  0 part /home
└─sda3   8:3    0  250G  0 part 
sdb      8:16   1   16G  0 disk 
└─sdb1   8:17   1   16G  0 part /media/usb

• NAME: Device name. For example, sda, sdb. The letters (a, b...) correspond to the order in which devices are detected by the system.
• SIZE: The size of the device.
• TYPE: The type of the device. For instance, disk is a physical disk, while part is its partition.
• MOUNTPOINT: The path where the device is mounted in the file system.

Useful Flags

lsblk is a pretty flexible command. By using additional options, you can get even more info:

• lsblk -f — shows the file system type and UUID (unique identifier) of each device.
• lsblk -o NAME,SIZE,FSTYPE,MOUNTPOINT — outputs only the columns you're interested in (like name, size, file system, mount point).

Example:

lsblk -f

Output:

NAME   FSTYPE LABEL    UUID                                 MOUNTPOINT
sda                                                         
├─sda1 ext4   rootfs   1111-2222-3333-4444                 /
├─sda2 ext4   home     5555-6666-7777-8888                 /home
└─sda3 swap            9999-AAAA-BBBB-CCCC                 [SWAP]
sdb    vfat   USB_DISK AAAA-BBBB                           /media/usb

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3. The blkid Command: The Magic of Unique Identifiers

Sometimes you need detailed info about a storage device or its file system. That’s where the blkid command comes in handy. Its job is to identify devices based on their file system and UUID.

Basics of the blkid Command

Run it without any parameters:

blkid

Example output:

/dev/sda1: UUID="1111-2222-3333-4444" TYPE="ext4"
/dev/sda2: UUID="5555-6666-7777-8888" TYPE="ext4"
/dev/sda3: UUID="9999-AAAA-BBBB-CCCC" TYPE="swap"
/dev/sdb1: UUID="AAAA-BBBB" TYPE="vfat" LABEL="USB_DISK"

• UUID: Unique partition identifier (doesn’t change, even if the device is renamed, e.g., from sda to sdb).
• TYPE: File system type.
• LABEL: Partition label.

Practical Use of UUID

UUID is super important in Linux because devices can dynamically change their names during boot. For instance, what’s called /dev/sda today might become /dev/sdb tomorrow. Thanks to UUID, you can use stable identification for mounting devices. We’ll discuss this further in the next lecture, where we’ll cover working with the /etc/fstab file.

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4. Working with Unmounted Devices

Sometimes you plug in a disk or flash drive, but it doesn’t show up as mounted. This might happen because there’s no active file system. Use lsblk and blkid to quickly figure out what’s going on.

Let’s say you connected a USB drive, but in the lsblk output you see:

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sdb      8:16   1   16G  0 disk 

This means that the sdb device doesn’t have an active partition. Check the blkid output to see if there’s a file system on it:

blkid /dev/sdb

If there’s no response, this confirms that the device isn’t formatted yet. We’ll talk about formatting in the next lecture.

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5. Comparison of lsblk and blkid

Both commands are super useful, but their uses are different:

• Use lsblk to get an overview of the whole system: where everything is, which partitions are mounted.
• Use blkid to get specific details about the file system (type, label, UUID).

Comparison Table

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6. Example: From Finding a Device to Understanding Its Structure

Task

1. Find the connected USB device.
2. Determine its file system.
3. Prepare the device for mounting.

Steps

1. Connect the device and run:

   lsblk
   

   Find your device. For example, sdb.

2. Check if a file system is present:

   blkid /dev/sdb
   

   If there's no file system, you'll get an empty output. This means the device needs to be formatted.

3. If a file system is present, you'll see its type and UUID. Now it can be used for further work (like mounting).

Now you're armed with knowledge to work with file systems in Linux. In the next lecture, we'll dive into formatting devices, creating file systems, and setting them up for operation! Get ready for the exciting process of turning a "raw" disk into a ready-to-use tool.