Cisco IOS Boot System Image

Can you please do an article on upgrading IOS XE versions? I ran into an issue in a working environment with this and couldn’t find too many resources for help out there.


Hello Waleed

If you have some suggestions for lessons to be included on Networklessons in the future, you can post those suggestions here:

Upgrading IOS XE versions is a good topic to include. Looking forward to hearing your ideas!


I got the solution. Just panic. I don’t understand what happened though.
It said right on the screen to do:

I did these two and it finished loading the flash file system.
Now the lights are blinking like they should. The system and the stat lights have stopped flashing.


I am in the library attempting lab 1-2 in ccnp switch lab manual 5:02 pm eastern.
I am attempting to clear my switches first.
I am getting a strange prompt before I attempt to clear my 3550- switch: . The port lights are solid. Only the system light and the rps light are blinking. I checked the power cord. Made sure it was pushed in properly. Gonna unplug and replug it back in. Could someone advise me as to what the issue is please or how I am getting this strange prompt?


Hello Yvette

This is strange behaviour indeed. When you attempted to clear the switch, what commands did you enter exactly? It may be that some vital system files were erased and the device was rebooted and it is no unable to fully boot itself due to missing files. Can you let us know a little more about the commands you used to “clear” the switch?


Hello Laz ,

Is there any way to boot and read from a file located in flash ?

Hello Spyros

When a Cisco device boots up, it will read the IOS image from the flash memory. It will do this by default. If you have more than one IOS file in the flash, then you must specify which one you want to boot up using the boot system command. For example, you can specify it in this way:

Router(config)#boot system flash c2800nm-adventerprisek9-mz.151-4.M12a.bin

I hope this has been helpful!


Thank you Lazare , i didn’t mean the ios .
Can i boot and read a config file from flash: ?
I need to avoid having the whole configuration in nvram and place it in flash:
only a specific configuration stored in nvram that shows in a file config file in flash.
I tried the boot config flash:test.cfg in an 2901 but it didn’t work .

Hello Spyro

I see, sorry I misunderstood. I would have suggested the command you mention, but I guess the 2901 does not support this. What does the command say if you type it in? Does it accept it? Try the following command and look at this output:

Router# show bootvar

 BOOT variable =
 CONFIG_FILE variable = nvram:
 Current CONFIG_FILE variable = slot0:router-config
 BOOTLDR variable not exist

 Configuration register is 0x0


The CONFIG_FILE variable shows from where the startup-config will be loaded. Check to see what your router says.

You can also try to use the boot config flash: command but just save your configuration as startup-config in the flash.

I hope this has been helpful!


Hi Lazaros,

When we use the boot system flash command to direct a switch or router to use that ios as the one to load do we have to look at the boot lines first with show run | i boot then use command
no boot system and reload all the lines in order or what we like or is boot system flash command sufficient . Also is there a way in switches and routers to change the number related to the ios file in order to force a certain boot order priority?

Thanks !

Hello Daniel

It’s always a good idea to check to see what boot commands are already configured on the device. You can have multiple boot system commands, and the device will execute the commands in the order in which you enter them in the config file. So if you simply enter one more boot system command, it will become the last option and will only be executed if all previous boot system commands fail.

If you only specify the flash as the source without additional parameters, then the router will boot from the “first bootable image” which I understand to be the first one as it appears alphabetically in the list of files. So if you have multiple IOS files, you can rename them so that they appear in a different order, just as long as you keep the .bin suffix.

Keep in mind that some platforms may behave differently than what I am describing, but this is the way most platforms function.

You can find out more about the boot system command here:

I hope this has been helpful!


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