This post about Linux df command opens series of articles for Linux newbies where you’ll find description and usage examples of major Linux commands like df, top, fsck, mount and so on.

Introduction

Linux df command can be used to display disk usage statistics for the file systems present on the Linux system. It’s handy tool to know which filesystem is consuming how much memory. Also, if a particular filename is picked up and supplied as argument to df command then it displays the disk usage statistics for the file system on which the file resides. This command can be used by the system administrators to know the disk usage status of various file systems on Linux so that proper clean-up and maintenance of the Linux system can be performed. The df command provides various options through which the output can be customized in a way that is most suited to the user.

In this article, we will discuss the df command through practical examples.

Syntax

Before jumping on to the examples, lets first take a look on how to use the df command. Here is the syntax information of df command from the man page:

df [OPTION]... [FILE]...

So we see that the df command does not require any mandatory argument. The OPTION and FILE arguments are non-mandatory. While the OPTION argument tells the df command to act in a way as specified by the definition of that OPTION, the FILE argument tells the df command to print disk usage of only that file system on which the FILE resides.

NOTE: for those who are new to this type of syntax information, any argument specified in square brackets [] are non-mandatory.

Examples

1. Basic example

Here is how the df command can be used in its most basic form.

# df 
Filesystem     1K-blocks    Used     Available Use% Mounted on 
/dev/sda6       29640780 4320704     23814388  16%     / 
udev             1536756       4     1536752    1%     /dev 
tmpfs             617620     888     616732     1%     /run 
none                5120       0     5120       0%     /run/lock 
none             1544044     156     1543888    1%     /run/shm

In the output above, the disk usage statistics of all the file systems were displayed when the df command was run without any argument.

The first column specifies the file system name, the second column specifies the total memory for a particular file system in units of 1k-blocks where 1k is 1024 bytes. Used and available columns specify the amount of memory that is in use and is free respectively. The use column specifies the used memory in percentage while the final column ‘Mounted on’ specifies the mount point of a file system.

2. Get the disk usage of file system through a file

As already discussed in the introduction, df can display the disk usage information of a file system if any file residing on that file system is supplied as an argument to it.

Here is an example:

# df test 
Filesystem     1K-blocks    Used      Available Use% Mounted on 
/dev/sda6       29640780    4320600   23814492  16%       /

Here is another example:

# df groff.txt 
Filesystem     1K-blocks    Used     Available Use% Mounted on 
/dev/sda6       29640780    4320600  23814492  16%     /

We used two different files (residing on same file system) as argument to df command. The output confirms that the df command displays the disk usage of file system on which a file resides.

3. Display inode information

There exists an option -i through which the output of the df command displays the inode information instead of block usage.

For example:

# df -i
Filesystem      Inodes    IUsed    IFree     IUse% Mounted on
/dev/sda6      1884160    261964   1622196   14%        /
udev           212748     560      212188    1%         /dev
tmpfs          216392     477      215915    1%         /run
none           216392     3        216389    1%         /run/lock
none           216392     8        216384    1%         /run/shm

As we can see in the output above, the inode related information was displayed for each filesystem.

4. Produce a grand total

There exists an option –total through which the output displays an additional row at the end of the output which produces a total for every column.

Here is an example:

# df --total 
Filesystem     1K-blocks    Used    Available Use% Mounted on 
/dev/sda6       29640780 4320720    23814372  16%     / 
udev             1536756       4    1536752   1%      /dev 
tmpfs             617620     892    616728    1%      /run 
none                5120       0    5120      0%      /run/lock 
none             1544044     156    1543888   1%      /run/shm 
total           33344320 4321772    27516860  14%

So we see that the output contains an extra row towards the end of the output and displays total for each column.

5. Produce output in human readable format

There exists an option -h through which the output of df command can be produced in a human readable format.

Here is an example:

# df -h 
Filesystem      Size  Used   Avail Use% Mounted on 
/dev/sda6       29G   4.2G   23G   16%     /  
udev            1.5G  4.0K   1.5G   1%     /dev 
tmpfs           604M  892K   603M   1%     /run 
none            5.0M     0   5.0M   0%     /run/lock 
none            1.5G  156K   1.5G   1%     /run/shm

So we can see that the output displays the figures in form of ‘G’ (gigabytes), ‘M’ (megabytes) and ‘K’ (kilobytes). This makes the output easy to read and comprehend and thus makes is human readable. Note that the name of the second column is also changed to ‘size’ in order to make it human readable.

Related Links

Manual for df
Index of Linux commands

 

5 Comments

 

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  2. November 10, 2012  8:44 pm by yo9gjx Reply

    Good post, a very usefull command, most common is "df -h", more humman view. ;)

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