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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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3 Answers

up vote 4 down vote accepted

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 '12 at 15:38
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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 y Aug 23 '12 at 8:05
    
No, it will not. –  Alex Aug 23 '12 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 '12 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 y Aug 23 '12 at 12:58
    
That is probably because before it mounts the root filesystem it had no / and no /var. And thus nowhere to write the log file. --- Does your VM allow you to set up a serial port? If it does then you could use a serial console? –  Hennes Aug 23 '12 at 13:18
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