Courseiva
SystemPrivileged EXEC

show file systems

Displays a list of all file systems available on the Cisco IOS device, including their type, permissions, and usage statistics, used for verifying storage availability and managing files.

Syntax·Privileged EXEC
show file systems

When to Use This Command

  • Checking available flash memory before copying a new IOS image
  • Verifying USB or external storage is recognized and writable
  • Troubleshooting 'no space left on device' errors when saving configurations
  • Identifying the correct file system prefix (e.g., flash0:) for file operations

Command Examples

Basic show file systems output

show file systems
File Systems:

      Size(b)       Free(b)      Type  Flags  Prefixes
    --------------  --------------  ----  -----  ------------------------------
    *   256901120     123456789     flash rw     flash0:
        256901120     123456789     flash rw     flash1:
               -              -     nvram rw     nvram:
               -              -     opaque rw     system:
               -              -     opaque rw     null:
               -              -     opaque ro     xmodem:
               -              -     opaque ro     ymodem:
               -              -     opaque rw     tftp:
               -              -     opaque rw     ftp:
               -              -     opaque rw     http:
               -              -     opaque rw     scp:
               -              -     opaque rw     https:
               -              -     opaque ro     cns:

The output lists all file systems. The asterisk (*) indicates the default file system. 'Size(b)' and 'Free(b)' show total and available bytes (dashes for network/opaque types). 'Type' indicates storage type (flash, nvram, opaque). 'Flags' show permissions: rw=read/write, ro=read-only. 'Prefixes' are the names used in commands (e.g., copy flash0:).

Checking flash space before upgrade

show file systems
File Systems:

      Size(b)       Free(b)      Type  Flags  Prefixes
    --------------  --------------  ----  -----  ------------------------------
    *   512000000      45000000     flash rw     flash0:
               -              -     nvram rw     nvram:
               -              -     opaque rw     tftp:

Here, flash0: has 512 MB total with only 45 MB free. This indicates low space; a new IOS image (typically 100-200 MB) would not fit. The nvram and tftp file systems show no size info because they are not fixed-size storage.

Understanding the Output

The 'show file systems' command displays a table with columns: Size(b) (total bytes), Free(b) (available bytes), Type (flash, nvram, opaque, etc.), Flags (rw=read/write, ro=read-only), and Prefixes (the file system name used in commands like copy, dir, delete). The asterisk marks the default file system. For flash and nvram, size and free values are shown; for network file systems (tftp, ftp, scp) and others (system, null, xmodem), these fields show dashes because they are not local storage. A low free space on flash (e.g., < 10% of total) indicates risk for file operations. Flags 'ro' mean you cannot write to that file system. This command is essential before any file transfer or upgrade to ensure sufficient space and correct permissions.

CCNA Exam Tips

1.

CCNA exam tip: The asterisk (*) indicates the default file system used when no prefix is specified in commands like 'copy' or 'dir'.

2.

CCNA exam tip: Know that 'flash0:' is typically the default, but if multiple flash file systems exist, the asterisk shows which one is active.

3.

CCNA exam tip: The 'opaque' type includes network file systems (tftp, ftp, scp) and virtual file systems (system, null). They show no size because they are not local storage.

4.

CCNA exam tip: If you see 'ro' flags on flash, the file system is read-only (e.g., if the switch is in ROMMON mode).

Common Mistakes

Mistake 1: Assuming all file systems have size information; network file systems like tftp: show dashes, which is normal.

Mistake 2: Forgetting to check free space before copying a file, leading to 'no space left on device' errors.

Mistake 3: Using the wrong prefix (e.g., 'flash1:' instead of 'flash0:') when multiple flash file systems exist, causing file operations to fail.

Related Commands

delete [file]

Deletes a file from the device's flash memory or other storage, used to remove unwanted configuration files, IOS images, or other stored data.

dir [flash:|nvram:|bootflash:]

Lists the contents of a specified file system (flash, nvram, or bootflash) on a Cisco IOS device, showing file names, sizes, dates, and available space.

show version

Displays system hardware and software information, including IOS version, uptime, memory, interfaces, and configuration register, used to verify device identity and software compatibility.

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