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Let say I have a headless linux server. Is it possible to read the messages that are displayed at the boot of the server in realtime, i.e. at the moment of the boot, with a "remote" computer ?

I know I can have access to these messages when boot is complete with dmesg but I would like to have it during the boot process.

  • Read using what, networking provided by the booting system, out-of-band system (Intel AMT etc), another device reading output from serial port? "Realtime" is a bit vague, you need to be a bit more specific on your setup/requirements. – sebasth Sep 11 '17 at 12:22
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    A network KVM would allow you to do this. – roaima Sep 11 '17 at 12:23
  • @meuh netconsole is exactly what I was searching for ! (Can you put it as an answer so that I can vote for the answer ?) @roaima ; the network KVM would be ok but requires an additional hardware – Regman Sep 12 '17 at 16:20
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Linux provides netconsole which is an output only equivalent of dmesg over the network using broadcast udp packets. If configured in the boot command, it starts sending as soon as the interface is up.

Note, for full console input/output, I have used in the past an ipkvm hardware device, as linked to in the comments by roaima, that plugs in to the usb and appears to the BIOS and OS as keyboard and mouse. It also plugs in to the VGA video ouput, and converts the analog signal back into an image which can be sent over the network to appear in your browser as an animated view of the system you can control completely at a distance. Presumably, hdmi versions of these exist too.

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