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Disk

Comprehensive Guide on Disk Analysis, I/O, and Mounting in Linux

Managing disk space, analyzing disk I/O performance, and properly mounting file systems are crucial tasks for system administrators. This guide covers essential Linux commands for these tasks, including dd, du, df, iostat, and mount.

Disk Analysis

1. Viewing Disk Usage with du

The du (disk usage) command estimates the space used by files and directories.

  • Basic Usage

To display the disk usage of a directory and its subdirectories:

bash du -h /path/to/directory

  • -h: Displays sizes in human-readable format (e.g., KB, MB, GB).

  • Summarize Disk Usage

To display the total size of a directory:

bash du -sh /path/to/directory

  • -s: Summarize, only shows the total size.

  • Analyze Disk Usage with Sorting

To analyze disk usage and sort the results:

bash du -hsx /var/lib/docker/* | sort -rh | head -n 35

  • -x: Skip directories on different file systems.
  • sort -rh: Sort by size in reverse order.
  • head -n 35: Display the top 35 entries.

Another example for /home directory:

bash du -hsx /home/* | sort -rh | head -n 35

2. Checking Disk Space with df

The df (disk free) command reports file system disk space usage.

  • Basic Disk Space Usage

To display disk space usage for all mounted file systems:

bash df -h

  • -h: Human-readable output.

  • Check Specific File System

To check the disk space usage of a specific file system:

bash df -h /dev/sda1

This will display information specific to the /dev/sda1 file system.

3. Disk I/O Analysis with iostat

The iostat command is used to monitor system I/O device loading by observing the time the devices are active relative to their average transfer rates.

  • Basic I/O Statistics

To display I/O statistics:

bash iostat

  • Detailed Report

To get a detailed report with extended statistics:

bash iostat -x

  • -x: Display extended statistics.

  • Monitoring I/O Continuously

To monitor I/O performance every few seconds:

bash iostat 5

This command will refresh the I/O statistics every 5 seconds.

Disk Operations

1. Copying Data at Binary Level with dd

The dd command is used to copy and convert files at a binary level. It’s commonly used for tasks like creating bootable USB drives, backing up disk partitions, and more.

  • Basic Copying

To copy data from one file or device to another:

bash dd if=/dev/sda of=/dev/sdb bs=64K conv=noerror,sync

  • if: Input file (source).
  • of: Output file (destination).
  • bs: Block size, here 64K is used.

  • conv=noerror,sync: Continue on read errors and pad the output with zeros to maintain sync.

  • Backup and Restore a Disk

To create an image of a disk:

bash dd if=/dev/sda of=/path/to/backup.img

To restore from the image:

bash dd if=/path/to/backup.img of=/dev/sda

  • Create a Bootable USB

To create a bootable USB from an ISO file:

bash dd if=/path/to/iso of=/dev/sdb bs=4M status=progress

  • status=progress: Displays the progress of the operation.

Mounting File Systems

Mounting is the process of making a file system accessible at a certain point in the Linux directory tree.

1. Basic Mounting

To mount a disk or partition:

sudo mount /dev/sdb1 /mnt
  • /dev/sdb1: The partition or disk to be mounted.
  • /mnt: The directory where the file system will be accessible.

2. Unmounting

To unmount a file system:

sudo umount /mnt

3. Persistent Mounting (Adding to /etc/fstab)

To automatically mount a file system at boot, add an entry to /etc/fstab.

Example entry for /dev/sdb1:

/dev/sdb1  /mnt  ext4  defaults  0  2
  • ext4: The file system type.
  • defaults: Default mount options.
  • 0 2: Dump (backup) and fsck (file system check) options.

4. Viewing Mounted File Systems

To view all currently mounted file systems:

mount | column -t

This command displays mounted file systems in a more readable format.

5. Useful Resource for Mounting Persistent Disks

For detailed instructions on mounting disks in cloud environments, you can refer to the following guide:

Conclusion

This guide provides a comprehensive overview of essential disk management commands in Linux. Understanding how to analyze disk usage, monitor I/O performance, and properly mount file systems is crucial for maintaining a healthy and efficient system.

These tools (dd, du, df, iostat, mount) are powerful and versatile, allowing you to perform a wide range of tasks, from simple file system checks to advanced disk operations. Always refer to the man pages (e.g., man dd, man du, man mount) for more detailed information and additional options.