[FAQ Index] [To Section 6 - Networking] [To Section 8 - General Questions]

7 - Keyboard and Display Controls

Table of Contents

7.1 - How do I remap the keyboard? (wscons)

The ports that use the wscons(4) console driver: alpha, amd64, hppa, i386, mac68k, macppc, sparc, sparc64, vax, and zaurus.

With wscons(4) consoles, most options can be controlled using the wsconsctl(8) utility. For example, to change keymappings with wsconsctl(8) one would execute the following:

# wsconsctl keyboard.encoding=uk

In the next example, we will remap "Caps Lock" to be "Control L":

# wsconsctl keyboard.map+="keysym Caps_Lock = Control_L"

7.2 - Is there console mouse support in OpenBSD?

For the alpha, amd64 and i386 platforms, OpenBSD provides wsmoused(8), a port of FreeBSD's moused(8). It can be enabled automatically at startup by copying and editing the appropriate line from rc.conf to rc.conf.local(8).

7.3 - Accessing the Console Scrollback Buffer (amd64, i386, some Alpha)

On some platforms, OpenBSD provides a console scrollback buffer. This allows you to see information that has already scrolled past your screen. To move up and down in the buffer, simply use the key combinations [SHIFT]+[PGUP] and [SHIFT]+[PGDN].

The default scrollback buffer, or the number of pages that you can move up and view, is 8. This is a feature of the vga(4) driver, so it will not work without a VGA card on any platform (many Alpha systems have TGA video).

Due to space limitations, the install kernels do not provide the scrollback function. Switching consoles will clear the scrollback buffer.

7.4 - How do I switch consoles? (amd64, i386, Zaurus, some Alpha)

On amd64, i386 and Alpha systems with vga(4) cards, OpenBSD provides six virtual terminals by default, /dev/ttyC0 through /dev/ttyC5. ttyC4 is reserved for use by the X Window system, leaving five text consoles. You can switch between them using [CTRL]+[ALT]+[F1], [CTRL]+[ALT]+[F2], [CTRL]+[ALT]+[F3], [CTRL]+[ALT]+[F4] and [CTRL]+[ALT]+[F6].

The X environment uses ttyC4, [CTRL]+[ALT]+[F5]. When using X, the [CTRL]+[ALT]+[Fn] keys will take you to the text screens; [CTRL]+[ALT]+[F5] will take you back to the graphical environment.

If you wish to have more than the default number of virtual consoles, use the wsconscfg(8) command to create screens for ttyC6, ttyC7 and above. For example:

wsconscfg -t 80x25 6
will create a virtual terminal for ttyC6, accessed by [CTRL]+[ALT]+[F7]. Don't forget to add this command to your rc.local(8) file if you want the extra screen the next time you boot the computer.

Note that you will not get a "login:" prompt on the newly-created virtual console unless you set it to "on" in /etc/ttys(5), and either reboot or send init(8) a HUP signal using kill(1).

On the Zaurus, two virtual terminals (/dev/ttyC0 and /dev/ttyC1) are available by default, accessible with [ALT]+[CALENDAR] and [ALT]+[ADDRESS] (The [ALT] key is the one right of the left [CTRL] key).

7.5 - How do I use a console resolution of 80x50? (amd64, i386, some Alpha)

amd64, i386, and VGA Alpha users normally get a console screen of 25 lines of 80 characters. However, many VGA video cards are capable of displaying a higher text resolution of 50 lines of 80 characters.

First, a font that supports the desired resolution must be loaded using the wsfontload(8) command. The standard 80x25 text screen uses 8x16 pixel fonts; to double the number of lines we will have to use 8x8 pixel fonts.

After that, we will have to delete and recreate a virtual console at the desired screen resolution, using the wsconscfg(8) command.

This can be done automatically at boot by adding the following lines to the end of your rc.local(8) file:

wsfontload -h 8 -e ibm /usr/share/misc/pcvtfonts/vt220l.808
wsconscfg -dF 5
wsconscfg -t 80x50 5
As with any modification to your system configuration, it is recommended you spend some time with the man pages to understand what these commands do.

The first line above loads the 8x8 font. The second line deletes screen 5 (which would be accessed by [CTRL]+[ALT]+[F6]). The third line creates a new screen 5 with 50 lines of 80 characters each. If you do this, you will see your primary screen, and the other three default virtual consoles, come up in the standard 80x25 mode, but a new screen 5 at 80x50 accessible through [CTRL]+[ALT]+[F6].

Remember that [CTRL]+[ALT]+[F1] is screen 0 (ttyC0). If you wish to alter other screens, simply repeat the delete and add screen steps for whichever screens you want running at the 80x50 resolution.

You should avoid changing screen 4 (ttyC4, [CTRL]+[ALT]+[F5]), which is used by X as a graphical screen. It is also not possible to change the resolution of the primary console device (i.e., ttyC0).

As one might expect, all these commands can also be entered at the command prompt, as root, or (better) using sudo(8).

Note: this will not work on all video cards. Unfortunately, not all video cards support the uploaded fonts that wscons(4) requires to achieve the 80x50 text mode. In these cases, you might wish to consider running X.

7.6 - How do I use a serial console?

There are many reasons you may wish to use a serial console for your OpenBSD system: OpenBSD supports serial console on most platforms, however details vary greatly between platforms.

Note that serial interfacing is NOT a trivial task -- you will often need unusual cables, and ports are not standardized between machines, in some cases, not even consistent on one machine. It is assumed you know how to select the appropriate cable to go between your computer and the device acting as your serial terminal. A full tutorial on serial interfacing is beyond the scope of this article, however, we offer one hint: just because the ends plug in doesn't mean it will work.

/etc/ttys change

There are two parts to getting a functional serial console on an OpenBSD system. First, you must have OpenBSD use your serial port as a console for status and single user mode. This part is very platform dependent. Second, you must enable the serial port to be used as an interactive terminal, so a user can log into it when running multi-user. This part is fairly similar between platforms, and is detailed here.

Terminal sessions are controlled by the /etc/ttys file. Before OpenBSD will give you a "login:" prompt at a device, it has to be enabled in /etc/ttys, after all, there are other uses for a serial port other than for a terminal. In platforms which typically have an attached keyboard and screen as a console, the serial terminal is typically disabled by default. We'll use the i386 platform as an example. In this case, you must edit the line that reads:

     tty00   "/usr/libexec/getty std.9600"   unknown off
to read something like:
     tty00   "/usr/libexec/getty std.9600"   vt220   on secure
Here, tty00 is the serial port we are using as a console. vt220 is the termcap(5) entry that matches YOUR terminal (other likely options might include vt100, xterm, etc.). The "on" activates the getty for that serial port so that a "login:" prompt will be presented, the "secure" permits a root (uid 0) login at this console (which may or may not be what you desire), and the "9600" is the terminal baud rate. Resist the urge to crank the baud rate up to the maximum your hardware can support, as you are more likely to create problems than benefit. Most systems have a "default" speed (supported by default by the boot ROM and/or the boot loader, often 9600), use this unless you have real reason to use something different.

Note that you can use a serial console for install without doing this step, as the system is running in single user mode, and not using getty for login.

On some platforms and some configurations, you must bring the system up in single user mode to make this change if a serial console is all you have available.

amd64 and i386

To direct the boot process to use the serial port as a console, create or edit your /etc/boot.conf file to include the line:
     set tty com0
to use the first serial port as your console. The default baud rate is 9600bps, this can be changed with a /etc/boot.conf line using the stty option. This file is put on your boot drive, which could also be your install floppy, or the command can be entered at the boot> prompt from the OpenBSD second-stage boot loader for a one-time (or first time) serial console usage.

amd64 and i386 notes:


These machines are designed to be completely maintainable with a serial console. Simply remove the keyboard from the machine, and the system will run serial.

SPARC and UltraSPARC notes


The MacPPC machines are configured for a serial console through OpenFirmware. Use the commands:
     ok setenv output-device scca
     ok setenv input-device scca
     ok reset-all
Set your serial console to 57600bps, 8N1.

MacPPC notes


Serial console is selected in the Booter program, under the "Options" pull-down menu, then "Serial Ports". Check the "Serial Console" button, then choose the Modem or Printer port. You will need a Macintosh modem or printer cable to attach to the Mac's serial ports. If you wish to have this as default, tell the Booter program to save your options.

Mac68k Notes

7.7 - How do I blank my console? (wscons)

If you wish to blank your console after a period of inactivity without using X, you can alter the following wscons(4) variables: You can set these variables at the command line using the wsconsctl(8) command:
     # wsconsctl display.screen_off=60000
     display.screen_off -> 60000
or set them permanently by editing /etc/wsconsctl.conf so these changes take place at next boot:
     display.vblank=on               # enable vertical sync blank
     display.screen_off=600000       # set screen blank timeout to 10 minutes
     display.kbdact=on               # Restore screen on keyboard input
     display.outact=off              # Restore screen on display output
The blanker is activated when either display.kbdact or display.outact is set to "on".


This is a feature, not a bug, actually.

Virtually all Unix commands and user names are entered using all lowercase. However, some very old terminals were only capable of uppercase characters, making them difficult, if not impossible, to use with Unix. As a workaround, if you entered your user name in all uppercase, getty(8) would assume your terminal was "lowercase challenged", and simply interpret everything you type as lowercase, while echoing it as uppercase. If you have a mixed-case or uppercase password, this will make login impossible.

Hitting CTRL-D at the login prompt will cause getty(8) to terminate, and init(8) will relaunch a new one, which will accept uppercase and lowercase properly.

7.9 - What is tmux?

For those familiar with the "screen" program, provided as a package, or window(1) which used to be in base, it may be easiest to answer this by saying that tmux(1) performs many of the functions as screen and window, with many additional features.

For those not familiar with these programs, tmux is a terminal multiplexer. This is a program which allows a number of other processes to share the same screen for input and output. In tmux, such a collection of programs is known as a session, with each program contained in a tmux window.

In addition to sharing the terminal, tmux lets you detach a session and its windows from the screen, leave them continue running in the background, and later reattach them to the same or to a different screen. A session may be detached manually or through an unexpected event such as network disconnection, in either case the programs survive and continue running as normal.

tmux also has many other features such as splitting a single window into multiple sections (known as panes), a history of text printed in each window, copying and pasting text between windows, configurable key bindings, and terminal locking. Take a look at the tmux(1) man page for further information.

How do I use tmux?

The first step is to run tmux:

$ tmux

This starts a new tmux with a single new session (called "0") and creates a client displaying it on screen. Most of the screen will show a window containing a shell prompt, and you will notice the last line is occupied by a status line. This shows the name of the session in square brackets on the left, the window title (normally empty for shells) and the time on the right, and a summary of the current open windows in the middle. In your new session, the currently open windows will contain one entry, for example:


A brief aside regarding terminals: on OpenBSD, applications are made aware of the capabilities of the terminal by the TERM environment variable. This is set to the name of an entry in the terminfo(5) database and tells programs that the terminal, for example, supports colour, or has the ability to insert lines, or many other things. An important thing to note is that the "xterm" entry in the database does not include colour, so tmux will not use colour in xterm by default, TERM should be set to "xterm-xfree86" instead if colour is desired (the "XTerm*termName" X resource may be set in .Xdefaults to use this for all xterms). It is also important that TERM in shells started inside tmux is set to "screen" or programs run from them may not display correctly - tmux will set this itself, but care should be taken not to override it in shell startup files.

Returning to the status line, the number "0" is the window index, "ksh" the name of the window, and the "*" indicates this is the current window displayed above the status line. Any typing is passed on to the shell and any output displayed. For example, if you start "top":

$ top

It will run as normal, occupying the part of the screen above the status line. You may also notice that the window name in the status line has changed from "ksh" to "top" - tmux renames windows to reflect the program currently running in them.

Now, let's say you want to detach tmux from the screen and return to the original shell from which you started it. A tmux session may be detached by first pressing the Ctrl and b keys together, and then the d key. The Ctrl-b key combination (shortened in tmux and its man page to "C-b") is known as the prefix key and is used to tell tmux that the next key pressed is an instruction that it should perform some action, rather than passing the key through to the program in the window.

After pressing Ctrl-b d and returning to the shell prompt, reattach the tmux session using the "attach" command:

$ tmux attach

The tmux session will reappear, with the status line and "top" still happily running. (If you instead run tmux again without arguments, a second session will be created, named "1".)

Next, let's create a second window. This is done using the "c" key: press the prefix key, Ctrl-b, then the "c" key. A new window will be created and again a shell prompt displayed on screen. The status line will be updated to show the new window:

0:top- 1:ksh*

The "-" after "top" shows the previously current window (the last window). Pressing Ctrl-b c again creates another new shell:

0:top  1:ksh- 2:ksh*

There are several commands for moving between windows. From window 2, you can move the previous window, number 1, by typing Ctrl-b p. Ctrl-b n moves to the next window: in this case, there is no window 3 so the current window wraps to window 0. You can also press Ctrl-b w to get an interactive menu of open windows, Ctrl-b l to move to the last window (the one marked with "-"), or Ctrl-b 0 to move to window 0, Ctrl-b 1 for window 1 and so on up to Ctrl-b 9 for window 9. So, to get back to "top" in window 0, you can press Ctrl-b 0 to go directly to window 0, Ctrl-b p twice to move via window 1, Ctrl-b n to wrap from window 2 to window 0, or press Ctrl-b w and select window 0 from the list.

Sometimes you may want to create a window running a program directly, without using a shell first. This can be done from the tmux command prompt. Pressing the Ctrl-b : key sequence changes the status line to display a ":" prompt at which commands may be entered. All the tmux commands are documented in the man page. In this case the "new-window" command is needed. Each command has a shorthand alias which may be used instead of typing the full name, for "new-window" this is "neww". So, to create a new window running tetris(6), type:

neww tetris

The new window will close when tetris exits, or may be forcibly killed using the Ctrl-b & key binding. This will first prompt for confirmation and if given, close the window and terminate the program running in it.

Another common requirement is renaming a window. This can be done with the Ctrl-b , key binding. The status line will change to display a "(rename-window)" prompt at which the new name may be entered. Renaming a window turns off automatic renaming for that window, to reenable that feature, press Ctrl-b : to get to the command prompt and enter the following (more on what this means is in the next section):

setw -u automatic-rename

One other important key is worth remembering: Ctrl-b ?. This will show a list of all the tmux keys and the commands they execute. For example, Ctrl-b ? shows that the c key is bound to the "new-window" command and the n key to the "next-window" command.

Configuring tmux

Many users want to customise the way tmux looks or behaves. This is done through the configuration file, ~/.tmux.conf. This file is a list of tmux commands which are executed when tmux is initially started, before the first session is created. All tmux commands are documented in the man page, but a few common examples you might want to put in your configuration file are discussed below.

The most common requirement is setting options. There are two types of option in tmux: session options and window options. Session options control the behaviour of a session and window options of an individual window. For both there is a set of global options. When tmux comes to decide on an options value for a particular session or window, it looks first at the options local to that window; if the option has not been set, the global option value is used.

Session options are set with the "set-option" (alias "set") command and window options with the "set-window-option" command (alias "setw"). To set a global option, use the "-g" flag, if this is left out the option is set for the current window or session. These commands also accept a few other flags, such as "-u" to unset a local option and allow a window or session to inherit the global option again.

In the configuration file, it is usual to set global options. Let's look at some examples customising the status line:

set -g status-bg blue
set -g status-right '#(sysctl vm.loadavg)'
setw -g window-status-current-attr underscore

Putting these three commands in .tmux.conf and restarting tmux changes the status line background to blue, puts the current load average on the right side and underlines the current window. The status line may be turned off entirely with:

set -g status off

There are a large number of other options; another handy one is changing to vi(1)-style key bindings at the command prompt and in the window list and other tmux interactive modes:

set -g status-keys vi
setw -g mode-keys vi

The current options and their values may be listed with the "show-options" and "show-window-options" commands. Like the set commands these accept "-g" to show the global options.

Another common task for the configuration file is adding or modifying tmux command key bindings, that is the commands that are executed after you press Ctrl-b with another key. These are added or changed with the "bind-key" command (alias "bind") and removed with the "unbind-key" command (alias "unbind"). Two examples of using "bind-key" are:

bind C-d detach
bind / neww 'exec top'

The first line creates a binding for Ctrl-b Ctrl-d to detach tmux, the same as the default Ctrl-b d, and the second binds Ctrl-b / to create a new window running top.

Many people like to use a different prefix key than Ctrl-b. This can be achieved using both the "set-option" and key binding commands to alter the prefix key option and change so that pressing the prefix twice continues to pass the same key through to the window. To change the prefix key to Ctrl-a:

set -g prefix C-a
unbind C-b
bind C-a send-prefix

The final useful thing to do in the configuration file is to create an initial set of windows when tmux starts. This is slightly more complicated than the previous examples. In tmux, a session cannot have no windows, and you cannot create windows without a session. So, to have windows created by the configuration file you must first create a session to contain them. For example (note that "new" is the alias for the "new-session" command):

new -d 'exec top'
neww -d
neww -d

These commands create a new session with "top" running in the first window, then create two additional windows. The "-d" flags instruct tmux not to try to attach the new session or to make the new windows the current window. Before putting these lines into .tmux.conf, there is one other issue. When executed without arguments, tmux runs the "new-session" command, so when starting tmux with "tmux" from the shell, the configuration file tells tmux to create one session, then the command from the shell tells it to create another, so you end up with two sessions. To avoid this, tmux should be started with "tmux attach" when creating a session from the configuration file - this means it will create the session from .tmux.conf then immediately attach to it without creating a second session.

Advanced tmux usage

This section briefly covers some of the more advanced features available in tmux. See the man page for more information.

In tmux, you can copy and paste text between windows. This is done by copying the text in copy mode and then pasting it with the paste command. To enter copy mode, press Ctrl-b [. In copy mode (with the "mode-keys" window option set to emacs, for vi keys see the man page) the arrow keys may be used to position the cursor, Ctrl-Space starts the selection and Ctrl-w copies. You can also use Page Up, Page Down, Ctrl-a and Ctrl-e to move the cursor around. Press q or Escape to exit copy mode. After that, Ctrl-b ] will paste the copied text into the current window as if you had typed it directly.

tmux is quite scriptable, and most commands that may be entered from the command prompt or bound to a key may be executed from the shell. Almost all tmux commands accept an optional "-t" argument which specifies the session or window on which to act. For example, this command:

$ tmux kill-window -t0:1
will kill window 1 in session 0. And:
$ tmux new-window -tmysession

creates a new window in the session named "mysession". Many commands accept other arguments, for example the "new-window" command accepts a "-n" option to give the name of the new window, and "new-session" accepts several arguments to specify the attributes of the initial window created with the session. These arguments may naturally be used when a command is bound to a key or executed from the command prompt as well.

Another useful feature is the ability to split a single window into several sections, called panes. You can split a window vertically (top to bottom) with the Ctrl-b " key combination. A pane can be resized up or down with Ctrl-b Alt-Up and Ctrl-b Alt-Down and the active pane changed with Ctrl-b o. In addition, a window split in that way may be changed into one of a number of fixed layouts, these are cycled through with Ctrl-b Space but panes in one of these layouts may not be resized. In -current, splitting has been extended to support horizontal splitting (Ctrl-b %) and the fixed layouts changed so they are applied once (with the same Ctrl-b Space key strokes) but then may be freely resized and modified both horizontally and vertically.

[FAQ Index] [To Section 6 - Networking] [To Section 8 - General Questions]

[back] www@openbsd.org
$OpenBSD: faq7.html,v 1.89 2010/05/19 12:41:02 nick Exp $