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Cisco ASA: “read-only file system”

by Jeremy L. Gaddis on March 21, 2012 · 4 comments

in Networking

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Recently, while upgrading a Cisco ASA that belongs to a customer and hasn’t been touched in a long time, the following took place:

ciscoasa# copy tftp flash

Address or name of remote host []? 10.10.10.42

Source filename []? asa842-k8.bin

Destination filename [asa842-k8.bin]?

Accessing tftp://10.10.10.42/asa842-k8.bin...!!!!!!!!!!!!!!!!!!!!!!!

...

Writing file disk0:/asa842-k8.bin...

%Error opening disk0:/asa842-k8.bin (Read-only file system)
ciscoasa#

Being fairly fluent in teh Lunix, I’ve seen a filesystem get mounted read-only several times — mostly when a server hasn’t been shut down correctly. But on an ASA? A read-only filesystem?

I thought to myself, “How the hell do you fix this?” and then, almost immediately, “I wonder if I can fsck the filesystem?”. And, as it turns out, I could.

fsck is short for “filesystem check” and is similar to chkdsk from the DOS/Windows world. I decided to give it a shot.

ciscoasa# fsck disk0
dosfsck 2.11, 12 Mar 2005, FAT32, LFN
Reclaimed 26 unused clusters (106496 bytes) in 3 chains.
Performing changes.
/dev/hda1: 49 files, 10065/31033 clusters

fsck of disk0: complete
ciscoasa#

Was it really that easy? There was only one way to find out.

ciscoasa# copy tftp flash

Address or name of remote host []? 10.10.10.42

Source filename []? asa842-k8.bin

Destination filename [asa842-k8.bin]?

Accessing tftp://10.10.10.42/asa842-k8.bin...!!!!!!!!!!!!!!!!!!!!!!!

...

Writing file disk0:/asa842-k8.bin...
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
...
25159680 bytes copied in 27.350 secs (931840 bytes/sec)
ciscoasa#
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