mjhjmtu

Linux embedded file system (Linux v. 2.6.26.5) running on raw NAND flash, it use Full Image's RootFS. U-boot 2009.03 bootloader. I need access shell after the Kernel is fully loaded, so that I can reset password.
For now I use busybox emergency shell, so Linux kernel not fully loaded, the root partition is not mounted, not all drivers are loaded and many commands not work. I need mount the root partition, but I don't know exactly what is the real root partition on /dev. Boot log contain some lines,

Kernel command line: console=ttyS1,115200n8 rootfstype=squashfs noalign half_image=0 verify=y

LINUX_ROOTFS is 4
VFS: Mounted root (squashfs filesystem) readonly.
...

I guess root can be /dev/mtdblock5, but not sure. What is correct command to mount the root partition?

mount /dev/mtdblock5 /

Also what is worst case scenario, if I don't guess partition and set it incorrectly?

edit: I tried fdisk

BusyBox v1.10.2 (2017-08-02 14:07:25 CST) built-in shell (ash)
Enter 'help' for a list of built-in commands.

/bin/sh: can't access tty; job control turned off
# fdisk -l 
/bin/sh: fdisk: not found
# 

# mount
mount: no /proc/mounts
#

# lsblk
/bin/sh: lsblk: not found

I managed mount /proc. But can't mount /dev, /sys.

# cd /
# mount -t dev dev /dev
mount: mounting dev on /dev failed: No such device
# mount -t proc proc /proc
# mount -t sys sys /sys
mount: mounting sys on /sys failed: No such device
# mount -t devpts devpts /dev/pts
mount: mounting devpts on /dev/pts failed: No such file or directory

For mount the partition the first step is know "where" is:

fdisk -l 

The answer must be something like this:

Disk /dev/sda: 931,5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x00009971

Device Boot Start End Sectors Size Id Type
/dev/sda1 2048 10547199 10545152 5G 82 Linux swap / Solaris
/dev/sda2 192243712 1953521663 1761277952 839,9G 7 HPFS/NTFS/exFAT
/dev/sda3 * 10547200 192243711 181696512 86,7G 83 Linux

In the last section you can see "where" are the partitions! Only rest mount them, with the comand you propose: "mount" (obviously :-) )

For the second question: I don't think you will broke something...in the worst scenario the prompt will give you an error.

Greetings

Sorry for the late answer, I only have internet in my work.

So, you can use lsblk instead fdisk, here are the results:

root@CyborgPC /h/cyborg# lsblk 
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 931,5G 0 disk 
├─sda1 8:1 0 5G 0 part [SWAP]
├─sda2 8:2 0 839,9G 0 part 
└─sda3 8:3 0 86,7G 0 part /
sr0 11:0 1 1024M 0 rom 

As you can see the sda2 partition is not mounted, I mount:

root@CyborgPC /h/cyborg# mount /dev/sda2 /media/cyborg/Almacen

And use the lsblk again:

root@CyborgPC /h/cyborg# lsblk 
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 931,5G 0 disk 
├─sda1 8:1 0 5G 0 part [SWAP]
├─sda2 8:2 0 839,9G 0 part /media/cyborg/Almacen
└─sda3 8:3 0 86,7G 0 part /
sr0 11:0 1 1024M 0 rom 

As you can see the lsblk give you the path where the device is found in /dev and, if it's mounted, give you the localization.

Hope you can solve your problem.