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I am trying to boot from a usb-hdd, which is supposed later to pass control to a full-fledged Ubuntu 18 installation, on a different HDD.

The usb-hdd has only the following directories and files:

- grub2 and its directory tree (including grub.cfg)
- the linux kernel (vmlinuz)
- initrd.

Grub is supposed to transfer control to the full-fledged system, using the command:

 linux   /boot/vmlinuz-5.0.0-37-generic root=UUID=23ac2c37-... ...-be3a8f82fdc1 ro

During the boot process, I am encountering all kinds of error messages, but they are printed on the console, and some of them disappear; also, sometimes it is necessary to turn the computer off manually; then dmesg and all buffers are gone (since there is no /var/log directory on the usb-hdd, and the full-fledged Ubuntu on a separate HDD has not been mounted yet).

Is there a grub.cfg command, (or a linux kernel parameter), to redirect the boot messages to a file? (or, even better, to "tee" them to a file?)

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  • You can use netconsole to send boot messages via UDP over the network, and process them on a second machine in any way you like.
    – dirkt
    Commented Jan 13, 2020 at 11:53
  • Nice. Post it as an answer.
    – Helen Craigman
    Commented Jan 13, 2020 at 17:51

1 Answer 1

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You can use netconsole to send boot messages via UDP over the network, and process them on a second machine in any way you like.

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