5 ms·

Not necessarily. With good timing and some luck, you can connect the serial/"recovery" console before GRUB's timeout ends and either change the running kernel o

by akx 4y ago

Not necessarily. With good timing and some luck, you can connect the serial/"recovery" console before GRUB's timeout ends and either change the running kernel or add the `systemd.mask=docker.service` boot parameter to prevent Docker from starting.

withinboredom 4y ago
Sounds like a VM and not a physical server.
- akx 4y ago
  Sure. For a physical server, you'd use its lights-out management to the same effect.
- laumars 4y ago
  Nope. Back before VMs were thing it was common to do "lights out" style remote management via a console server. That console server would then have a serial connection (the old 9 pin d-sub plug[1]) to your individual physical servers. You could then connect to your remote servers local TTY via the console server a little like jumping to remote servers via an SSH bastion. However it did sometimes require a little bit of prior configuration, depending on your distro[2]. This wasn't just limited to Linux either. It was a common UNIX trick :) This is a bit of a lost art these days though. iLo, IPMI have replaced the need for serial. Then virtualisation and, to a lesser extent, containerisation have lowered the bar even further plus also moving the industry towards more ephemeral systems that can be destroyed and rebuilt automatically rather than the old habits of nursing failed hosts back to health. [1] https://duckduckgo.com/?q=9+pin+d-sub+plug&t=newext&atb=v316-1&iar=images&iax=images&ia=images https://duckduckgo.com/?q=9+pin+d-sub+plug&t=newext&atb=v316... [2] https://www.kernel.org/doc/html/v5.3/admin-guide/serial-console.html https://www.kernel.org/doc/html/v5.3/admin-guide/serial-cons... (a lot of distros at the time did ship a kernel with this support compiled in. I don't know how common it is now).
  - jacquesm 4y ago
    And quite a few implementations actually emulate the serial console allowing for the exact same access. (Serial Over Lan or SOL for short.)
  - topranks 4y ago
    Still common on network devices (Cisco, Juniper, Arista etc.). No IPMI or similar on those. Console servers from the likes of OpenGear and Lantronix still heavily used for those.

by akx 4y ago

withinboredom 4y ago

Sounds like a VM and not a physical server.

akx 4y ago
Sure. For a physical server, you'd use its lights-out management to the same effect.
laumars 4y ago
Nope. Back before VMs were thing it was common to do "lights out" style remote management via a console server. That console server would then have a serial connection (the old 9 pin d-sub plug[1]) to your individual physical servers. You could then connect to your remote servers local TTY via the console server a little like jumping to remote servers via an SSH bastion. However it did sometimes require a little bit of prior configuration, depending on your distro[2]. This wasn't just limited to Linux either. It was a common UNIX trick :) This is a bit of a lost art these days though. iLo, IPMI have replaced the need for serial. Then virtualisation and, to a lesser extent, containerisation have lowered the bar even further plus also moving the industry towards more ephemeral systems that can be destroyed and rebuilt automatically rather than the old habits of nursing failed hosts back to health. [1] https://duckduckgo.com/?q=9+pin+d-sub+plug&t=newext&atb=v316-1&iar=images&iax=images&ia=images https://duckduckgo.com/?q=9+pin+d-sub+plug&t=newext&atb=v316... [2] https://www.kernel.org/doc/html/v5.3/admin-guide/serial-console.html https://www.kernel.org/doc/html/v5.3/admin-guide/serial-cons... (a lot of distros at the time did ship a kernel with this support compiled in. I don't know how common it is now).
- jacquesm 4y ago
  And quite a few implementations actually emulate the serial console allowing for the exact same access. (Serial Over Lan or SOL for short.)
- topranks 4y ago
  Still common on network devices (Cisco, Juniper, Arista etc.). No IPMI or similar on those. Console servers from the likes of OpenGear and Lantronix still heavily used for those.