Linux console
The Linux console is a system console internal to the Linux kernel. The Linux console provides a way for the kernel and other processes to send text output to the user, and to receive text input from the user. The user typically enters text with a computer keyboard and reads the output text on a computer monitor. The Linux kernel supports virtual consoles — consoles that are logically separate, but which access the same physical keyboard and display.
This article describes the basics of the Linux console and how to configure the font display. Keyboard configuration is described in the /Keyboard configuration subpage.
Contents
Implementation
This article or section needs expansion.
The console, unlike most services that interact directly with users, is implemented in the kernel. This contrasts with terminal emulation software, such as Xterm, which is implemented in user space as a normal application. The console has always been part of released Linux kernels, but has undergone changes in its history, most notably the transition to using the framebuffer and support for Unicode.
Despite many improvements in the console, its full backward compatibility with legacy hardware means it is limited compared to a graphical terminal emulator.
Virtual consoles
The console is presented to the user as a series of virtual consoles. These give the impression that several independent terminals are running concurrently; each virtual console can be logged in with different users, run its own shell and have its own font settings. The virtual consoles each use a device /dev/ttyX , and you can switch between them by pressing Alt+Fx (where x is equal to the virtual console number, beginning with 1). The device /dev/console is automatically mapped to the active virtual console.
Text mode
This article or section needs expansion.
Since Linux originally began as a kernel for PC hardware, the console was developed using standard IBM CGA/EGA/VGA graphics, which all PCs supported at the time. The graphics operated in VGA text mode, which provides a simple 80×25 character display with 16 colours. This legacy mode is similar to the capabilities of dedicated text terminals, such as the DEC VT100 series. It is still possible to boot in text mode if the system hardware supports it, but almost all modern distributions (including Arch Linux) use the framebuffer console instead.
Framebuffer console
As Linux was ported to other non-PC architectures, a better solution was required, since other architectures do not use VGA-compatible graphics adapters, and may not support text modes at all. The framebuffer console was implemented to provide a standard console across all platforms, and so presents the same VGA-style interface regardless of the underlying graphics hardware. As such, the Linux console is not a terminal emulator, but a terminal in its own right. It uses the terminal type linux , and is largely compatible with VT100.
Keyboard shortcuts
| Keyboard Shortcut | Description |
|---|---|
| Ctrl+Alt+Del | Reboots the system (specified by the symlink /usr/lib/systemd/system/ctrl-alt-del.target ) |
| Alt+F1 , F2 , F3 , . | Switch to n-th virtual console |
| Alt+ ← | Switch to previous virtual console |
| Alt+ → | Switch to next virtual console |
| Scroll Lock | When Scroll Lock is activated, input/output is locked |
| Ctrl+c | Kills current task |
| Ctrl+d | Inserts an EOF |
| Ctrl+z | Pauses current Task |
Fonts
This article or section needs expansion.
By default, the virtual console uses the kernel built-in font with a CP437 character set, [1] but this can be easily changed.
The Linux console uses UTF-8 encoding by default, but because the standard VGA-compatible framebuffer is used, a console font is limited to either a standard 256, or 512 glyphs. If the font has more than 256 glyphs, the number of colours is reduced from 16 to 8. In order to assign correct symbol to be displayed to the given Unicode value, a special translation map, often called unimap, is needed. Nowadays most of the console fonts have the unimap built-in; historically, it had to be loaded separately.
The kbd package provides tools to change virtual console font and font mapping. Available fonts are saved in the /usr/share/kbd/consolefonts/ directory, those ending with .psfu or .psfu.gz have a Unicode translation map built-in.
Keymaps, the connection between the key pressed and the character used by the computer, are found in the subdirectories of /usr/share/kbd/keymaps/ , see /Keyboard configuration for details.
Preview and temporary changes
shows a table of glyphs or letters of a font.
setfont temporarily change the font if passed a font name (in /usr/share/kbd/consolefonts/ ) such as
Font names are case-sensitive. With no parameter, setfont returns the console to the default font.
So to have a small 8×8 font, with that font installed like seen below, use e.g.:
To have a bigger font, the Terminus font ( terminus-font ) is available in many sizes, such as ter-132n which is large.
Источник
Linux Serial Console¶
To use a serial port as console you need to compile the support into your kernel — by default it is not compiled in. For PC style serial ports it’s the config option next to menu option:
Character devices ‣ Serial drivers ‣ 8250/16550 and compatible serial support ‣ Console on 8250/16550 and compatible serial port
You must compile serial support into the kernel and not as a module.
It is possible to specify multiple devices for console output. You can define a new kernel command line option to select which device(s) to use for console output.
The format of this option is:
You can specify multiple console= options on the kernel command line. Output will appear on all of them. The last device will be used when you open /dev/console . So, for example:
defines that opening /dev/console will get you the current foreground virtual console, and kernel messages will appear on both the VGA console and the 2nd serial port (ttyS1 or COM2) at 9600 baud.
Note that you can only define one console per device type (serial, video).
If no console device is specified, the first device found capable of acting as a system console will be used. At this time, the system first looks for a VGA card and then for a serial port. So if you don’t have a VGA card in your system the first serial port will automatically become the console.
You will need to create a new device to use /dev/console . The official /dev/console is now character device 5,1.
(You can also use a network device as a console. See Documentation/networking/netconsole.rst for information on that.)
Here’s an example that will use /dev/ttyS1 (COM2) as the console. Replace the sample values as needed.
Create /dev/console (real console) and /dev/tty0 (master virtual console):
LILO can also take input from a serial device. This is a very useful option. To tell LILO to use the serial port: In lilo.conf (global section):
Adjust to kernel flags for the new kernel, again in lilo.conf (kernel section):
Make sure a getty runs on the serial port so that you can login to it once the system is done booting. This is done by adding a line like this to /etc/inittab (exact syntax depends on your getty):
Init and /etc/ioctl.save
Sysvinit remembers its stty settings in a file in /etc , called /etc/ioctl.save . REMOVE THIS FILE before using the serial console for the first time, because otherwise init will probably set the baudrate to 38400 (baudrate of the virtual console).
/dev/console and X Programs that want to do something with the virtual console usually open /dev/console . If you have created the new /dev/console device, and your console is NOT the virtual console some programs will fail. Those are programs that want to access the VT interface, and use /dev/console instead of /dev/tty0 . Some of those programs are:
It should be fixed in modern versions of these programs though.
Note that if you boot without a console= option (or with console=/dev/tty0 ), /dev/console is the same as /dev/tty0 . In that case everything will still work.
Thanks to Geert Uytterhoeven @ linux-m68k . org> for porting the patches from 2.1.4x to 2.1.6x for taking care of the integration of these patches into m68k, ppc and alpha.
© Copyright The kernel development community.
Источник
Linux Serial Console¶
To use a serial port as console you need to compile the support into your kernel — by default it is not compiled in. For PC style serial ports it’s the config option next to menu option:
Character devices ‣ Serial drivers ‣ 8250/16550 and compatible serial support ‣ Console on 8250/16550 and compatible serial port
You must compile serial support into the kernel and not as a module.
It is possible to specify multiple devices for console output. You can define a new kernel command line option to select which device(s) to use for console output.
The format of this option is:
You can specify multiple console= options on the kernel command line. Output will appear on all of them. The last device will be used when you open /dev/console . So, for example:
defines that opening /dev/console will get you the current foreground virtual console, and kernel messages will appear on both the VGA console and the 2nd serial port (ttyS1 or COM2) at 9600 baud.
Note that you can only define one console per device type (serial, video).
If no console device is specified, the first device found capable of acting as a system console will be used. At this time, the system first looks for a VGA card and then for a serial port. So if you don’t have a VGA card in your system the first serial port will automatically become the console.
You will need to create a new device to use /dev/console . The official /dev/console is now character device 5,1.
(You can also use a network device as a console. See Documentation/networking/netconsole.txt for information on that.)
Here’s an example that will use /dev/ttyS1 (COM2) as the console. Replace the sample values as needed.
Create /dev/console (real console) and /dev/tty0 (master virtual console):
LILO can also take input from a serial device. This is a very useful option. To tell LILO to use the serial port: In lilo.conf (global section):
Adjust to kernel flags for the new kernel, again in lilo.conf (kernel section):
Make sure a getty runs on the serial port so that you can login to it once the system is done booting. This is done by adding a line like this to /etc/inittab (exact syntax depends on your getty):
Init and /etc/ioctl.save
Sysvinit remembers its stty settings in a file in /etc , called /etc/ioctl.save . REMOVE THIS FILE before using the serial console for the first time, because otherwise init will probably set the baudrate to 38400 (baudrate of the virtual console).
/dev/console and X Programs that want to do something with the virtual console usually open /dev/console . If you have created the new /dev/console device, and your console is NOT the virtual console some programs will fail. Those are programs that want to access the VT interface, and use /dev/console instead of /dev/tty0 . Some of those programs are:
It should be fixed in modern versions of these programs though.
Note that if you boot without a console= option (or with console=/dev/tty0 ), /dev/console is the same as /dev/tty0 . In that case everything will still work.
Thanks to Geert Uytterhoeven @ linux-m68k . org> for porting the patches from 2.1.4x to 2.1.6x for taking care of the integration of these patches into m68k, ppc and alpha.
Источник
Linux Serial Console¶
To use a serial port as console you need to compile the support into your kernel — by default it is not compiled in. For PC style serial ports it’s the config option next to menu option:
Character devices ‣ Serial drivers ‣ 8250/16550 and compatible serial support ‣ Console on 8250/16550 and compatible serial port
You must compile serial support into the kernel and not as a module.
It is possible to specify multiple devices for console output. You can define a new kernel command line option to select which device(s) to use for console output.
The format of this option is:
You can specify multiple console= options on the kernel command line. Output will appear on all of them. The last device will be used when you open /dev/console . So, for example:
defines that opening /dev/console will get you the current foreground virtual console, and kernel messages will appear on both the VGA console and the 2nd serial port (ttyS1 or COM2) at 9600 baud.
Note that you can only define one console per device type (serial, video).
If no console device is specified, the first device found capable of acting as a system console will be used. At this time, the system first looks for a VGA card and then for a serial port. So if you don’t have a VGA card in your system the first serial port will automatically become the console.
You will need to create a new device to use /dev/console . The official /dev/console is now character device 5,1.
(You can also use a network device as a console. See Documentation/networking/netconsole.txt for information on that.)
Here’s an example that will use /dev/ttyS1 (COM2) as the console. Replace the sample values as needed.
Create /dev/console (real console) and /dev/tty0 (master virtual console):
LILO can also take input from a serial device. This is a very useful option. To tell LILO to use the serial port: In lilo.conf (global section):
Adjust to kernel flags for the new kernel, again in lilo.conf (kernel section):
Make sure a getty runs on the serial port so that you can login to it once the system is done booting. This is done by adding a line like this to /etc/inittab (exact syntax depends on your getty):
Init and /etc/ioctl.save
Sysvinit remembers its stty settings in a file in /etc , called /etc/ioctl.save . REMOVE THIS FILE before using the serial console for the first time, because otherwise init will probably set the baudrate to 38400 (baudrate of the virtual console).
/dev/console and X Programs that want to do something with the virtual console usually open /dev/console . If you have created the new /dev/console device, and your console is NOT the virtual console some programs will fail. Those are programs that want to access the VT interface, and use /dev/console instead of /dev/tty0 . Some of those programs are:
It should be fixed in modern versions of these programs though.
Note that if you boot without a console= option (or with console=/dev/tty0 ), /dev/console is the same as /dev/tty0 . In that case everything will still work.
Thanks to Geert Uytterhoeven @ linux-m68k . org> for porting the patches from 2.1.4x to 2.1.6x for taking care of the integration of these patches into m68k, ppc and alpha.
Источник
