[c-nsp] FYI on the "verify" command for Sup720 "disk" flash

[Charles Spurgeon]

FYI.  This is another "heads up," this time on the topic of image
verification on Sup720 flash devices that are called "disk" in the IOS
filesystem (eg "disk0:").

We had a data center Sup720 fail to reload recently due to an image
read failure. The image had been downloaded with FTP and the resulting
image file on the disk0 flash was the correct size. However, the
Sup720 failed to reload on the image.

After the router was rebooted on a sup-bootflash image we ran the
"verify" command on the disk0 image which showed that there was a
consistent read error on that disk0 image. Who knows -- maybe there
was a bad cell on the flash.

After some research we found that unlike other flash types, automatic
image verification does not occur on downloads to flash called
"disk<n>". Instead, you need to run "verify" to ensure that the image
downloaded OK and reads correctly.

As a result of all this, we've added the verify command to the scripts
that stage code onto the Sup720s for reload. A verify on the latest
82MB SXF5 image takes about 2 1/2 minutes to complete.

Note that running the verify command on a "disk" image generates a
confusing message: 
"%Filesystem does not support verify operations".

AFAICT, this is a reference to the fact that the "disk" type of flash
file system does not automatically support image verification, and can
be ignored.

Here's a Cisco doc on using the verify command:
http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a0080455c55.html

Beware of setting automatic verification in the config file as shown
in this doc, since it will then find any bootable image types on all
flash known to IOS (including the flash in an FWSM or other
controllers) and may halt and prompt for a user response on checking
those images.

-Charles

Charles E. Spurgeon / UTnet
UT Austin ITS / Networking
c.spurgeon at its.utexas.edu / 512.475.9265

===========================================================================
Output of verify command:
++++++++++++++++++++++++++++++
lab-sup720B#verify disk0:72033-advipservicesk9_wan-mz.122-18.SXF5.bin
%Filesystem does not support verify operations
Verifying file integrity of
disk0:s72033-advipservicesk9_wan-mz.122-18.SXF5.bin.............................

(approx 2.5 minutes later)
........................Done!
Embedded Hash   MD5 : F58447BA8336E536A64CFE25B152000F
Computed Hash   MD5 : F58447BA8336E536A64CFE25B152000F
CCO Hash        MD5 : 20D0AA30811D46A0BA3719EB793303DF

Signature Verified
++++++++++++++++++++++++++++++