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Linux df Command: Display File System Hard Disk Usage

The df command in Linux (short for "disk free") is a utility used to display the amount of disk space used and available on file systems. This tutorial will cover how to use the df command effectively, along with various options and examples.

Basic usage of the df command:
To display disk space usage for all mounted file systems, simply run the df command without any options:
```
df
```
This will show output similar to the following:
```
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda1            10238440   3716476   6014616  39% /
tmpfs                  515324        92    515232   1% /run
/dev/sdb1            20479928   3340292  16185200  18% /mnt/data
```
The output includes the file system, size, used and available space, usage percentage, and mount point.
Displaying disk space usage in human-readable format:
To display disk space usage in a more human-readable format (using kilobytes, megabytes, or gigabytes), use the -h or --human-readable option:
```
df -h
```
This will show output similar to the following:
```
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1       9.8G  3.6G  5.8G  39% /
tmpfs           503M   92K  503M   1% /run
/dev/sdb1        20G  3.2G   15G  18% /mnt/data
```
Displaying disk space usage for specific file systems:
To display disk space usage for specific file systems, pass the desired file system or mount point as an argument:
```
df /dev/sda1
```
This will show the disk space usage only for the specified file system.
Displaying disk space usage in a specific unit:
To display disk space usage in a specific unit (e.g., megabytes or gigabytes), use the --block-size option:
```
df --block-size=M
```
This command will display disk space usage in megabytes. You can replace M with K for kilobytes or G for gigabytes.

Displaying the file system type:

To display the file system type along with disk space usage, use the -T or --print-type option:

df -Th

This will show output similar to the following:

Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/sda1      ext4      9.8G  3.6G  5.8G  39% /
tmpfs          tmpfs     503M   92K  503M   1% /run
/dev/sdb1      ext4       20G  3.2G   15G  18% /mnt/data

By following this tutorial, you should now have a good understanding of how to use the df command in Linux to display disk space usage for file systems. The df command is a helpful tool for monitoring disk usage and managing storage resources effectively.

How to use df command in Linux: The df command in Linux is used to display disk space usage information. A basic usage example is:
```
df
```
This command shows information about mounted filesystems along with their sizes, used space, and available space.
Checking disk space usage with df: To check disk space usage, use:
```
df -h
```
The -h option displays sizes in a human-readable format (e.g., KB, MB, GB).
Displaying disk space in human-readable format with df: The -h option is used to display disk space in a human-readable format:
```
df -h
```
This makes the output easier to read by using units like KB, MB, and GB.
Showing specific file system usage using df: To display information about a specific filesystem, specify the mount point:
```
df -h /path/to/mount/point
```
Replace /path/to/mount/point with the actual mount point.
Monitoring disk space trends with df: To monitor disk space trends over time, you can use tools like watch to update the df output periodically:
```
watch -n 5 df -h
```
This updates the disk space information every 5 seconds.
Excluding certain file systems from df output: To exclude specific filesystems from the df output, you can use the -x option:
```
df -x tmpfs -h
```
This excludes tmpfs filesystems from the output.
Checking available inodes with df in Linux: To check available inodes (index nodes) along with disk space:
```
df -i
```
This provides information on used and available inodes.
Automating disk space checks with df and cron: To automate disk space checks, you can create a cron job:
```
0 * * * * df -h > /path/to/logfile.log
```
This example runs the df command every hour and appends the output to a log file.
Troubleshooting low disk space issues using df: If you encounter low disk space, identify large directories with:
```
du -h --max-depth=1 /
```
This helps troubleshoot and locate where disk space is being consumed.