topic CBS250-48 fails to boot, enters "Embedded Linux" in Switching

CBS250-48 fails to boot, enters "Embedded Linux"

Michal_546897 — Mon, 21 Jul 2025 11:59:18 GMT

Hi,
one of our new CBS250-48T-4x switches fails to boot, when connecting via console I see it boots to some weird Embedded Linux environment, full console info in attachment, here is few first and last lines

Few last lines

mount: mounting ubi0 on /mnt/flash failed: Device or resource busy
Filesystem 1K-blocks Used Available Use% Mounted on
none 131072 4 131068 0% /dev/shm
ubi0 223636 128720 90080 59% /mnt/flash
[Pegatron] PHY interrupt init... done
[Pegatron] Serdes init... done
[Pegatron] Cascade init... done
[Pegatron] MPP setting... done
[Pegatron] LED init... done
[Pegatron] Auto learning... done
[Pegatron] System LED green on

[Pegatron] Pegatron version v0.9.1(20211227)
***************************************************
Pegatron Corp Initial Done
***************************************************

Re: CBS250-48 fails to boot, enters "Embedded Linux"

Enes Simnica — Mon, 21 Jul 2025 12:05:51 GMT

hello G. What u're seeing, the switch booting into the Pegatron Embedded Linux environment, usually means the main Cisco OS image is either missing, corrupted, or failed to load properly. Pegatron is the hardware manufacturer for the CBS250, and this shell is part of the low-level bootloader environment, not the normal Cisco Business Switch OS.

This typically happens after an interrupted upgrade, power loss during boot, or a corrupted image. The line in your logs that says:

mount: mounting ubi0 on /mnt/flash failed: Device or resource busy

and this suggests that the system couldn't mount the flash where the main OS lives, so it dropped into this fallback shell.

What you’ll want to do is attempt a recovery:

Reboot the switch while connected via console.
Try to interrupt the boot process (you might see prompts like “Press Ctrl+C”, “ESC”, or “Space”).
If you can access the bootloader, you may be able to re-flash the image using a USB drive or via Xmodem over the console (slow but works).

Here’s the official Cisco software page to download the right image for your model (CBS250-48T-4X):
https://software.cisco.com/download/home

let me know if u need more help, and hope it helps...

-Enes

Re: CBS250-48 fails to boot, enters "Embedded Linux"

Enes Simnica — Mon, 21 Jul 2025 12:07:38 GMT

also this one:

https://www.cisco.com/c/en/us/td/docs/switches/lan/csbms/CBS_250_350/Administration-Guide/cbs-250-ag/cbs_250_chapter_01.html

Re: CBS250-48 fails to boot, enters "Embedded Linux"

Michal_546897 — Tue, 22 Jul 2025 06:35:17 GMT

Thank you ! I was able to push image via Xmodem, specifically using tool "Terra Term" for future reference, at the start of the bootloader booting process you'll get prompt "Press x to choose XMODEM..." so press X and within Terra Term go File > Transfer > XMODEM > Send .
It took around an hour at 115200 speed and after that switch automatically booted into the healthy image.
Thanks again !

Re: CBS250-48 fails to boot, enters "Embedded Linux"

Enes Simnica — Tue, 22 Jul 2025 11:11:48 GMT

@Michal_546897 glad I could help G. Enjoy ur time with the CBS250, cause it’s an awesome device man.....