grub2 always adds "memtest86 serial console" even when no serial port

[tz]

Binary package hint: grub2

I have a laptop that does not and will never have an ordinary serial port.

Yet grub2 insists on adding the memory test for serial console that WILL NEVER WORK!.

There appears to be no way to disable this.

For some reason nodes are created in /dev for ttyS0 through ttyS3, but there is no underlying device. stty will return error, as will "cat". They are like a hanging symlink.

[h1repp (heinz-repp)]

confirming - a newly installed Lucid Netbook Edition to my Asus EeePC 1000h added a memtest serial (115000 bps) boot option to the boot menu - pretty useless.

[Colin Watson (cjwatson)]

Quite true, but the memtest86+ package controls this, so reassigning.

[Michael Richardson (mcr-sandelman)]

Actually, you likely do have hardware for the serial ports. It's part of the legacy ISA stuff in your north bridge.
Just your laptop does not have the pins hooked up to a DB9. My laptop's docking station exposes those.

What I think is that memtest86 should look for console= in the kernel config file, and not add the serial console unless
kernel has one.

[tz (thomas-mich)]

No, my netbook has nothing at the corresponding ports or interrupt vectors.

But to expand on your point, few have the special hardware to connect a serial console, so this shold be off unless someone has the knowledge to turn it on

[The Loeki (the-loeki)]

As a related comment, the serial port is *always* ttyS0, even when it's not there, and even when both GRUB2 itself and the kernel are all configured to go to, say ttyS1 or something completely else.

I propose to modify /etc/grub.d/20_memtest86+

* Look at /sys/class/tty/ ; if there's nothing in there that's not virtual (there should be a good way to weed out the virtual devices by looking at this), skip the serial port config
* AND/OR look at GRUB2/the kernel; if they're not configured for serial communication, why should you for memtest?

[Fantu (fantonifabio)]

the latest version now in Jammy include some option that can be added to /etc/default/grub:

  * Don't add grub2 entries if GRUB_DISABLE_MEMTEST=true is present
    in /etc/default/grub (LP: #420967)
  * Make possible disable serial with GRUB_MEMTEST_DISABLE_SERIAL,
    enable multiboot with GRUB_MEMTEST_ENABLE_MULTIBOOT and add
    custom serial parameters with GRUB_MEMTEST_SERIAL_PARAMS
    (Closes: #898636, #612371)