Unable to reconfigure Dell FN 410s switch modules

Ok, I got it figured out and I'm posting here for the Interwebz to remember for me:

To reset the password on an a Dell FN IOM module (in my case, a FN410s).

Powercycle the switch. I opened two ssh connections to the CMC and then used one connection to connect -m switch-1 to get a terminal connection to the switch. I needed to do this because none of the attempts I used to connect to the console port actually worked. The switch will then come up and begin to load the OS image. Ctrl-C to stop the processing and you'll get the root prompt for the OS. This is apparently running NetBSD.

$ connect -m switch-2
connect: acquiring remote port.
Connected to remote port.
Escape character is '^\'.
done.
WARNING: CHECK AND RESET THE DATE!
Reading Release Image at 0x3c0000 Part: A
Size of ReleaseImage is 46621345 Bytes
^C# 

Get a list of drives:

# sysctl -a | grep disk                                                        
sysctl: warning: /var/run/dev.db: No such file or directory
kern.bufq.strategies = disksort fcfs
hw.disknames = ld0 md0

ld0 is the drive while md0 is the in-memory file system

Check your partitions on ld0:

# disklabel /dev/ld0
# /dev/ld0c:
type: ld
disk: SD4G
label: IOMSTOMP_4G_v3
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 64
sectors/cylinder: 4032
cylinders: 1957
total sectors: 15702016
rpm: 7200
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # microseconds
track-to-track seek: 0  # microseconds
drivedata: 0 

8 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:      2048         4       swap                     # (Cyl.      0*-      0*)
 b:      2048      2052       swap                     # (Cyl.      0*-      1*)
 c:  15702016         0     unused      0     0        # (Cyl.      0 -   3894*)
 e:   3145728      4100      MSDOS                     # (Cyl.      1*-    781*)
 f:      2048   3149828       swap                     # (Cyl.    781*-    781*)
 g:   4404020   3151876       swap                     # (Cyl.    781*-   1873*)
 h:   8146120   7555896     4.2BSD      0     0     0  # (Cyl.   1873*-   3894*)

Notice the MSDOS partition, that's where the config file is. Mount it:

# mount /dev/ld0e /mnt2
# cd /mnt2
# ls
ADMIN_DIR           RUNTIME_PATCH_DIR   earlyCliParserDbg   pdtrc.lo0
CONFD_LOG_DIR       TRACE_LOG_DIR       last-cold-st-config startup-config
CORE_DUMP_DIR       boots.txt           normalReload        startup-config.bak

There's the startup config.

cat startup-config gives us the full file. The lines we're interested in are these:

enable password 7 b12545XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
!
username root password 7 30b400XXXXXXXXXXXXXXXXXXXXXXXXXX privilege 15

There is no vi, emacs or nano, but it does have sed so you have all you need to change the startup config file. Use echo to put lines into a sed file you will use to modify the startup-config:

echo /^enable password/s/^/!/ > sed.txt
echo /username root/s/password 7 30b400XXXXXXXXXXXXXXXXXXXXXXXXXX/password 0 password1234/ >> sed.txt

These commands comment out the enable command and change the root password to the super-secret 'password1234' stored with no hash. You will of course change this when you've gained access to the switch, right? Move the current startup-config to backup and then run sed to output the changes to the new startup-config:

mv startup-config startup-config.bak
sed -f sed.txt startup-config.bak > startup-config

Check to make sure your changes are correct and power cycle the switch

Enter the console again and try to log in with the corrected username and password:

Mar 25 16:24:15 %STKUNIT0-M:CP %SNMP-6-SNMP_COLD_START: Agent Initialized - SNMP COLD_START.

% Error: Authentication failed.
Login: root
Password: 
Mar 25 16:24:29 %STKUNIT0-M:CP %SEC-5-LOGIN_SUCCESS: Login successful for user root on console 


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switch-2#

Bingo, you're in.