Know how to use Cisco IOS file system commands

After setting up a Cisco
router, many administrators don’t upgrade the IOS
or access files on the Flash drive for quite a while. However, that doesn’t
mean there won’t come a time when you
need to manipulate the files on the Flash drive.

Working with the files and directories on the Cisco IOS file
system (Cisco IFS) involves using the same types of commands as when
manipulating files in Windows from the DOS command prompt. These commands include
copy, dir, and format.

Here are some of the common uses of these commands:

• Back
  up the IOS before an upgrade.
• Perform
  an upgrade.
• Back
  up the configuration file before making changes.
• View
  text files on disk (such as a backup configuration file).
• Restore
  the Cisco IOS to a router.

Let’s look at some of the Cisco IFS commands you need to
know. By keeping some of the more commonly used commands in mind when upgrading
and moving files to and from network devices, you can save time and perhaps
even prevent a disaster.

dir

The dir command
shows files in a directory, and the default directory is usually the Flash file
system. So, entering dir displays the directory of
flash:/ by default.

You can also specify which directory you want to view, or you
can use the all-filesystemsoption.
You can even use the /recursive
switch if you want to view files in subdirectories.

Here’s an example:

Router# dir
Directory of flash:/

1 -rw- 15183868  c2600-ik9o3s3-mz.122-15.T9.bin

16777216 bytes total (1592488 bytes free)
Router#

copy

While most people are familiar with the general copy command, it involves a little more
than just copying files from one place to another on a router or switch. In
fact, this command is critically important to copying files to and from the router.

For example, to upgrade the IOS on
a router, you must copy the new IOS from either the network or from a
locally attached console port (via something like xmodem). You can also use the
copy command to back up the
configuration on both the router and over the network, as well as to restore the
configuration from the network back to the router.

When using the copy
command, you can use standard URL format to identify both the source and
destination. Here’s an example of what the URL path looks like for a network
destination:

tftp:[[//location]/directory]/filename
ftp:[[//[username[:password]@]location]/directory]/filename

Below is an example of what the URL path looks like for a
local file system. In this example, the path to the startup-config for the
router is nvram:startup-config.

prefix:[directory/]filename

For example, you could back up a startup-configuration to a
TFTP server’s directory called router1, with an IP address of 1.1.1.1, using
this same URL structure. Here’s what it would look like:

Copy nvram:startup-configuration tftp://1.1.1.1/router1/startup-backup-2-8-2006

show file

The show file
command displays information about a specified file or file system. I consider
this a “little-known” command because it typically doesn’t get a lot
of use.

The show file
command’s most useful options are show
file information, which displays information about a specified file, and show file systems, which displays
information about the file systems.
Here’s an example:

Router# show file systems 
File Systems:

 Size(b) Free(b) Type Flags Prefixes
 29688 28899 nvram rw nvram:
 - - opaque rw system:
 - - opaque rw null:
 - - opaque ro xmodem:
 - - opaque ro ymodem:
 - - network rw tftp:
* 16777216 1592488 flash rw flash:
 - - network rw rcp:
 - - network rw pram:
 - - network rw ftp:
 - - network rw scp:
Router#

more

The more command
shows a text file. This command works just like it does in Linux—it allows you
to view a file on a disk. In the case of the Cisco IOS, you can use this command to
view a text file, such as your configuration file or a saved backup configuration
file. Here’s an example:

Router# more nvram:startup-config

delete

This command does just as it implies—it deletes files. There’s
really nothing special about this command, except for one thing: Depending on
the type of router, deleting a file may not actually free up the file space the
file was using. To reclaim the space the deleted files were using, you may need
to use the squeeze command.

erase or format

Depending on the type of memory you’re using, you can use
either the erase or format command to wipe out the Flash
drive. The erase command is the more common command used.

When copying files, you must be very careful to answer no to
the question of whether you want to erase the file system. Here’s an example:

Router# copy running-config flash:test
Destination filename [test]? 
Erase flash: before copying? [confirm]

If you just press [Enter] and accept the default answer, you’ll
delete the IOS file when trying to back up your router’s configuration to Flash.

cd and pwd

You can use the cd
command to change directories, which works the same way in DOS and Linux. This
command changes the directory to whichever directory you specify. You can use
the pwd command to print the working
directory, which also works the same way in Linux.

Let’s look at an example. Notice that using the dir command displays the new working
directory—the nvram file system—instead of the Flash default.

Router# cd nvram:

Router# pwd
nvram:/

Router# dir
Directory of nvram:/

 27 -rw- 0  startup-config
 28 ---- 0  private-config

29688 bytes total (29636 bytes free)
Router#

mkdir and
rmdir

Some routers and switches offer the ability to create and delete
directories. You can use the mkdir
command to create a directory, and the rmdir
command will remove a specified directory. Obviously, you would need to use the
cd and pwd commands to change into these directories.

For more information on how to use these commands, check out
Cisco’s Using
the Cisco IOS Integrated File System documentation.

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David Davis has worked
in the IT industry for 12 years and holds several certifications, including
CCIE, MCSE+I, CISSP, CCNA, CCDA, and CCNP. He currently manages a group of
systems/network administrators for a privately owned retail company and
performs networking/systems consulting on a part-time basis.