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I've installed FreeBSD inside a VM on a laptop. As it turns out, the laptop keyboard has no Scroll Lock key, which is used for scrolling the screen back in FreeBSD's console. How can I scroll back the output without Scroll Lock?

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    The question itself contained the answer I was looking for. My keyboard has Scroll Lock, but I didn't know I could use it!
    – mwfearnley
    Oct 27, 2017 at 14:49

3 Answers 3

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As root, dump the keyboard map to a file

kbdcontrol -d > mykeys

Change the file so "Ctrl+NumLock" will set "Scroll Lock". Find line with scancode "base" 069, or where "nlock" fills the entire line. Edit column 3 from "nlock" to "slock". The line now looks like:

"069   nlock  nlock  slock  nlock  nlock  nlock  nlock  nlock   O"

As root, issue the command:

kbdcontrol -l mykeys

The solution was found here.

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    For People using FreeBSD as a guest OS in a VirtualBox virtual machine on Mac OS X you can also remap Cntrl-Caps Lock. 058 clock clock slock clock clock clock clock clock O Typing Control-Caps Lock lets you scroll back on the console as far as the scrollback goes. Bliss!
    – Coroos
    Oct 8, 2012 at 15:38
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    since this is a top result, I'll add that to make this change permanent (after reboot) follow the steps above, and then mv mykeys /usr/share/syscons/keymaps/mykeys.kbd then edit your rc.conf file and add a line with keymap="mykeys"
    – aron.duby
    Oct 6, 2014 at 15:57
  • This does not work through ssh. Any tip on how to make it work?
    – Pablo Lalloni
    Oct 10, 2016 at 23:41
  • @Pablo Lalloni: these steps work for the syscons on the system you are connecting to with ssh. You need to perform the equivalent steps on the system you are connecting from. I say "equivalent steps" because if you are using Windows, Mac or Linux to connect to the FreeBSD system, the steps will be different.
    – CyberFonic
    Apr 28, 2021 at 5:43
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Laptop keyboards usually have a Fn key so that keys on a normal PC keyboard can be replicated. You should find that some combination of Fn and another key (hint: look for the blue text on your keys) will perform Scroll Lock. For instance, on my cheap netbook, Fn-F12 performs Scroll Lock.

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I use tmux for that, you can install it from ports under /usr/ports/sysutils/tmux. Ctrl-b PgUp and Ctrl-b PgDn allow to scroll the console output in tmux. BTW, tmux has other great features, basically it is an advanced screen replacement.

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  • WIll it allow to scroll back the output which was before starting tmux? Actually, I want to see all the boot messages, i.e. the output till login.
    – Eugene Yarmash
    Aug 23, 2012 at 8:05
  • No, it will not.
    – Alex
    Aug 23, 2012 at 8:08
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    The boot message are stored in a file called dmesg.boot. less /var/run/dmesg.boot might help you.
    – Hennes
    Aug 23, 2012 at 11:06
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    @Hennes This file contains only part of the messages, up to mounting the root filesystem. I needed the rest.
    – Eugene Yarmash
    Aug 23, 2012 at 12:58
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    @Hennes dmesg.boot does contain everything since the kernel was started. It does not contain the bootstrap loader messages or any BIOS messages that weren't cleared.
    – Chris S
    Oct 8, 2012 at 15:49

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