Linux CLI Essentials for Debian Users – Part 8: Disk Management

Master Debian CLI: Explore Disk Management Tools & Skills - Your Essential Guide to Efficient Linux System Maintenance

Introduction:

In our final voyage through the world of Debian Linux command-line essentials (CLI), we embark on this concluding chapter of our comprehensive guide. Let’s reflect on the knowledge you’ve acquired thus far.

In the previous section, you delved into the intricacies of file compression, archive management, and text processing. You honed your skills with commands like tar, gzip, gunzip, unzip, awk, and sed, mastering the art of efficiently handling data and manipulating text.

Now, as we delve into Disk Management, you’ll uncover the fundamental tools and concepts that empower you to manage storage devices, partitions, and file systems within the this environment. This section covers crucial commands such as libblk, fdisk, pvcreate, and vgcreate. Moreover, we’ll explore the foundational concepts of Volume Group (VG) and Logical Volume Manager (LVM), providing you with a comprehensive understanding of these essential CLI components.

As you progress through this section, keep in mind that Disk Management is a cornerstone of maintaining an organized and efficient Linux system. Whether you’re dealing with disk partitions, physical volumes, or volume groups, the commands and knowledge you acquire here will be invaluable in your CLI journey.

Disk Management

59. liblk - List information about block devices:

The lsblk command is used to list information about block devices on a Linux system. Block devices are typically storage devices like hard drives, solid-state drives, and partitions. This command provides an overview of the storage devices connected to your system and their details.

Syntax: Here’s the basic syntax of the lsblk command:

lsblk [options]

Now, let’s break down the components and explain how they work with examples:

• lsblk: This is the main command that you’re running.
• [options]: These are optional modifiers that you can include to customize the output or filter the devices displayed.

Examples: Commonly used options and modifiers for lsblk:

1. -a or --all: This option shows all devices, including empty ones.

   lsblk -a
   

2. -b or --bytes: Display sizes in bytes.

   lsblk -b
   

3. -d or --nodeps: Avoid displaying dependencies.

   lsblk -d
   

4. -f or --fs: Display filesystem-related information.

   lsblk -f
   

5. -i or --ascii: Use ASCII characters for tree printing.

   lsblk -i
   

6. -m or --ascii: Use megabytes for size display.

   lsblk -m
   

7. -o or --output: Specify the columns to be displayed. You can choose from various columns like NAME, TYPE, SIZE, MOUNTPOINT, etc. For example, to display only the device name and size, you can use:

   lsblk -o NAME,SIZE
   

8. -p or --pairs: Display output as key-value pairs, which can be useful for scripting.

   lsblk -p
   

9. -t or --tree: Display the device tree.

   lsblk -t
   

10. -h or --help: Show a help message with usage information for lsblk.

   lsblk -h

Example output of lsblk:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 232.9G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
├─sda2   8:2    0   488M  0 part /boot
└─sda3   8:3    0 231.9G  0 part /
sdb      8:16   0 931.5G  0 disk 
└─sdb1   8:17   0 931.5G  0 part /mnt/data

In this example, lsblk displays information about two storage devices (sda and sdb) along with their partitions, sizes, and mount points (if applicable). This information can be valuable for managing storage devices and understanding the disk layout of your system.

60. fdisk - Disk partitioning and management:

The fdisk command is used for disk partitioning and management on Linux systems. It allows you to create, delete, modify, and display partitions on a storage device like a hard drive or solid-state drive (SSD). This command is a powerful tool for managing disk partitions, but it should be used with caution as it can have a significant impact on your data and system.

Syntax: Here’s the basic syntax of the fdisk command:

fdisk [options] [device]

Now, let’s break down the components and explain how they work with examples:

• fdisk: This is the main command for disk partitioning.
• [options]: These are optional modifiers that you can include to customize the behavior of the fdisk command.
• [device]: This is the path to the device you want to manage, such as a hard drive or SSD. It should be specified as something like /dev/sda.

Examples: Commonly used options and modifiers for fdisk:

1. -l or --list: This option is used to list partition information for all available devices. It’s a read-only operation and provides a summary of existing partitions.

   fdisk -l
   

2. -c or --compatibility: This option enables compatibility mode, which is useful when working with older systems or non-Linux operating systems.

   fdisk -c /dev/sda
   

3. -u or --units: This option allows you to specify the display unit for sizes (cylinders, sectors, or bytes).

   fdisk -u sectors /dev/sdb
   

4. -p or --list-partition-tables: This option is used to list known partition tables for devices.

   fdisk -p
   

5. -w or --wipe: This option is used to write a signature to the device. Be cautious when using this option, as it can destroy data on the device.

   fdisk -w /dev/sdc
   

6. -H or --heads: This option allows you to specify the number of heads for the disk geometry.

   fdisk -H 255 /dev/sda
   

7. -S or --sectors: This option allows you to specify the number of sectors per track for the disk geometry.

   fdisk -S 63 /dev/sdb
   

8. -C or --cylinders: This option allows you to specify the number of cylinders for the disk geometry.

   fdisk -C 1024 /dev/sdc
   

9. -l or --largest-new: This option is used when creating a new partition to automatically select the largest available size.

   fdisk -l /dev/sdd
   n # for new partition
   # ... follow prompts ...
   

Please note that creating, deleting, or modifying partitions using fdisk requires superuser (root) privileges, often achieved using the sudo command.

Example of using fdisk to create a new partition:

sudo fdisk /dev/sde

# Command (m for help): n (for new partition)
# Partition type:
#    p   primary (0 primary, 0 extended, 4 free)
#    e   extended
# Select (default p): p
# Partition number (1-4, default 1): 1
# First sector (2048-41943039, default 2048): (press Enter to use default)
# Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): (press Enter to use default)

# Command (m for help): w (to write changes)

This example creates a new primary partition on the /dev/sde device.

Please exercise caution when using fdisk, especially when making changes to partitions, as it can lead to data loss if used improperly.

61. Volume Group (VG):

• A Volume Group (VG) is a fundamental component of the Logical Volume Manager (LVM) system on Linux.

• It is essentially a collection or pool of physical volumes (PVs) that are grouped together to form a larger storage unit.

• Volume Groups are created to provide a flexible and scalable way to manage storage devices such as hard drives, solid-state drives, or partitions.

• Once you’ve created a VG, you can allocate space from it to create Logical Volumes (LVs), which are essentially your usable partitions or storage volumes.

• VGs offer benefits like dynamic resizing of LVs, spanning across multiple physical disks, and the ability to manage storage efficiently.

62. Logical Volume Manager (LVM):

• The Logical Volume Manager (LVM) is a software-based storage management system that is used in Linux and Unix-like operating systems.

• LVM allows for more flexible and dynamic management of storage resources compared to traditional partition-based systems.

• Key components of LVM include Volume Groups (VGs), Logical Volumes (LVs), and Physical Volumes (PVs).

• Physical Volumes (PVs): These are the physical storage devices (like hard drives or partitions) that are added to LVM. PVs are initialized using the pvcreate command.

• Volume Groups (VGs): VGs are created by combining one or more PVs. They act as storage pools from which you can allocate space for LVs.

• Logical Volumes (LVs): LVs are analogous to partitions in traditional storage systems. They are created within VGs and can be resized dynamically. LVs can be used as if they were regular disk partitions.

• LVM offers advantages like online resizing of LVs, snapshots, easy backup and restore, and better space utilization.

In summary, a Volume Group (VG) is a key component of the Logical Volume Manager (LVM) system, serving as a pool of physical storage devices. LVM, on the other hand, is a comprehensive storage management system that provides dynamic and flexible storage solutions, allowing you to create Logical Volumes (LVs) within Volume Groups for better resource allocation and management.

63. pvcreate - used to initialize physical volumes for use in LVM:

The pvcreate command is used to initialize physical volumes (PVs) for use in the LVM (Logical Volume Manager) system on Linux. Physical volumes are disk partitions or entire storage devices that are managed by LVM. pvcreate prepares these devices or partitions to be used in LVM by adding LVM-specific metadata to them.

Syntax: Here’s the basic syntax of the pvcreate command:

pvcreate [options] [device(s)]

Now, let’s break down the components and explain how they work with examples:

• pvcreate: This is the main command for initializing physical volumes.
• [options]: These are optional modifiers that you can include to customize the behavior of the pvcreate command.
• [device(s)]: This is the path to the device or devices that you want to initialize as physical volumes. You can specify multiple devices if needed.

Examples: Commonly used options and modifiers for pvcreate:

1. -v or --verbose: This option displays detailed information about the initialization process, including progress and results.

   pvcreate -v /dev/sdb
   

2. -f or --force: This option forces the initialization even if the specified device appears to contain data. Be cautious when using this option, as it can result in data loss.

   pvcreate -f /dev/sdc
   

3. -y or --yes: This option automatically answers “yes” to all prompts during the initialization process. It’s useful when automating tasks with scripts.

   pvcreate -y /dev/sdd
   

4. -u or --uuid: This option specifies a specific UUID (Universally Unique Identifier) for the physical volume. UUIDs are used to uniquely identify volumes in the LVM system.

   pvcreate -u <uuid> /dev/sde
   

5. -y or --metadatacopies: This option allows you to specify the number of copies of the metadata that will be stored on the device. By default, one copy is created.

   pvcreate --metadatacopies 2 /dev/sdf
   

6. -M or --metadatatype: This option allows you to specify the metadata format type. You can choose between “lvm1” (the default) and “lvm2.”

   pvcreate --metadatatype lvm2 /dev/sdg
   

Example of using pvcreate to initialize a physical volume:

pvcreate /dev/sdh

This command initializes the /dev/sdh device as a physical volume for LVM. After running this command, the device is ready to be included in volume groups (VGs) and used for creating logical volumes (LVs).

Please note that the pvcreate command should be used carefully, especially when specifying the -f (force) option, as it can result in data loss on the specified device. Always make sure to back up any important data before initializing a physical volume.

64. vgcreate - create a new volume group within the LVM:

The vgcreate command is used to create a new volume group (VG) within the LVM (Logical Volume Manager) system on Linux. A volume group is a collection of physical volumes (PVs) that are grouped together to provide storage for logical volumes (LVs). vgcreate initializes a new volume group and associates one or more physical volumes with it.

Syntax: Here’s the basic syntax of the vgcreate command:

vgcreate [options] <VG name> [PV(s)]

Now, let’s break down the components and explain how they work with examples:

• vgcreate: This is the main command for creating a new volume group.
• [options]: These are optional modifiers that you can include to customize the behavior of the vgcreate command.
• <VG name>: This is the name you choose for the new volume group.
• [PV(s)]: This is an optional list of physical volumes (devices or partitions) that you want to associate with the new volume group. You can specify one or more PVs.

Examples: Commonly used options and modifiers for vgcreate:

1. -v or --verbose: This option displays detailed information about the creation process, including the PVs being added to the volume group.

   vgcreate -v myvg /dev/sdb /dev/sdc
   

2. -s or --physicalextentsize: This option specifies the physical extent size for the volume group. The default size is 4 MB, but you can change it if needed.

   vgcreate -s 8M myvg /dev/sdb
   

3. -A or --autobackup y/n: This option specifies whether or not metadata should be backed up automatically after each change to the volume group. Use “y” for yes and “n” for no.

   vgcreate -A y myvg /dev/sdb
   

4. -v or --verbose: This option displays detailed information about the creation process, including the PVs being added to the volume group.

   vgcreate -v myvg /dev/sdb /dev/sdc
   

Example of using vgcreate to create a new volume group:

vgcreate myvg /dev/sdb /dev/sdc

This command creates a new volume group named “myvg” and associates the physical volumes /dev/sdb and /dev/sdc with it. The newly created volume group is now ready to be used for creating logical volumes (LVs).

It’s important to note that before running vgcreate, you should initialize the physical volumes (pvcreate) that you intend to use in the volume group. Additionally, you should ensure that the necessary LVM packages are installed on your system for these commands to work.

Conclusion:

Throughout this section, you’ve immersed yourself in the critical domain of Disk Management, gaining mastery over the tools and concepts essential for maintaining a well-organized system.

Your journey through the CLI landscape has equipped you with a diverse skill set, encompassing system administration, file management, network diagnostics, and now, disk management. With these skills, you’re well-prepared to tackle a wide range of tasks and challenges in the Linux environment.

As we conclude this guide, you’ve not only gained practical expertise but also developed a deeper understanding of the CLI’s inner workings. Remember that the command-line interface is a powerful tool that empowers you to interact with your system efficiently.

As you continue your journey, the knowledge you’ve acquired here will serve as a solid foundation. Whether you’re a seasoned user or just beginning your CLI adventure, these essentials will remain valuable in your pursuit of mastering the Debian operating system.