kernel 4.1.2-bone 12, how to edit default cmdline

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1

Hi all.
System starts with

0.000000] Kernel command line: console=ttyO0,115200n8 root=UUID=250d80ed-1acd-4cc5-906f-2af2805ff23d ro rootfstype=ext4 rootwait fixrtc

even if there is nothing defined in uEnv.txt

Where and how i can edit default cmdline?
Thanks

2

System starts with
0.000000] Kernel command line: console=ttyO0,115200n8 root=UUID=250d80ed-1acd-4cc5-906f-2af2805ff23d ro rootfstype=ext4 rootwait fixrtc
even if there is nothing defined in uEnv.txt

Permanently or just once in a while?

See u-boot.cfg in u-boot repo for the default configuration otherwise explore the u-boot console.

3

Hi all.
System starts with
0.000000] Kernel command line: console=ttyO0,115200n8 root=UUID=250d80ed-1acd-4cc5-906f-2af2805ff23d ro rootfstype=ext4 rootwait fixrtc
even if there is nothing defined in uEnv.txt

Where and how i can edit default cmdline?
Thanks

The ‘cmdline’ variable in /boot/uEnv.txt

4

Yes, cmdline is in uEnv.txt, but even when it’s empty/hashed, kernel still gets Kernel command line: console=ttyO0,115200n8 root=UUID=250d80ed-1acd-4cc5-906f-2af2805ff23d ro rootfstype=ext4 rootwait fixrtc,
I assume it is in uboot.cfg?, thanks you both

5

Hmm, I can’t find uboot.cfg in bb-kernel folder, where else can I look?

6

NO, your assumption about uboot.cfg is incorrect:

/boot/uEnv.txt

Regards,

7

Ok, probably it is not needed anymore. What is defined in uEnv.txt is just added to the end of kernel comand (cmdline=console=ttyS0,115200n8).
Doesn’t look as pretty as it could look, but works.

[ 0.000000] Kernel command line: console=ttyO0,115200n8 root=UUID=f0fe05d6-8783-46b7-8e05-4cccb006b84c ro rootfstype=ext4 rootwait fixrtc console=ttyS0,115200n8
[ 3.066245] console [ttyS0] disabled
[ 3.846121] console [ttyS0] enabled

8

Humm, the kernel will rename ttyO0 -> ttyS0 automaticly... no reason
to add console twice..

Regards,

9

:slight_smile: Yes Robert, but:

  1. I didn’t like to see an error
  2. I wanted to test console on different tty
  3. W wanted to find out how to disable console on ttyS0.

I plan to use debug header as RS232 port for one of devices I am connecting to BBB.

Thank you anyway, Robert
It is pleasure to work with BBB, thanks to work you do with kernels, patches, dtbs’es, images and etc etc

10

add this to /boot/uEnv.txt:

console=ttyO0,115200n8

(and set it to anything you want and it'll override the default value
set in u-boot)

Regards,

11

in u-boot it's added to the cmdline via:

console=${console}

Regards,

12

Thank you very much.