diff options
| -rw-r--r-- | Documentation/serial-console.txt | 66 |
1 files changed, 35 insertions, 31 deletions
diff --git a/Documentation/serial-console.txt b/Documentation/serial-console.txt index 9a7bc8b3f479..1d9a3e48e929 100644 --- a/Documentation/serial-console.txt +++ b/Documentation/serial-console.txt @@ -1,15 +1,19 @@ - Linux Serial Console +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 "Standard/generic (dumb) serial support". +it's the config option next to menu option: + +:menuselection:`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: +The format of this option is:: console=device,options @@ -28,11 +32,11 @@ 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: +you open ``/dev/console``. So, for example:: console=ttyS1,9600 console=tty0 -defines that opening /dev/console will get you the current foreground +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. @@ -44,61 +48,61 @@ 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 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.) +``Documentation/networking/netconsole.txt`` for information on that.) -Here's an example that will use /dev/ttyS1 (COM2) as the console. +Here's an example that will use ``/dev/ttyS1`` (COM2) as the console. Replace the sample values as needed. -1. Create /dev/console (real console) and /dev/tty0 (master virtual - console): +1. Create ``/dev/console`` (real console) and ``/dev/tty0`` (master virtual + console):: - cd /dev - rm -f console tty0 - mknod -m 622 console c 5 1 - mknod -m 622 tty0 c 4 0 + cd /dev + rm -f console tty0 + mknod -m 622 console c 5 1 + mknod -m 622 tty0 c 4 0 2. 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): + In lilo.conf (global section):: - serial = 1,9600n8 (ttyS1, 9600 bd, no parity, 8 bits) + serial = 1,9600n8 (ttyS1, 9600 bd, no parity, 8 bits) 3. Adjust to kernel flags for the new kernel, - again in lilo.conf (kernel section) + again in lilo.conf (kernel section):: - append = "console=ttyS1,9600" + append = "console=ttyS1,9600" 4. 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): + like this to ``/etc/inittab`` (exact syntax depends on your getty):: - S1:23:respawn:/sbin/getty -L ttyS1 9600 vt100 + S1:23:respawn:/sbin/getty -L ttyS1 9600 vt100 -5. Init and /etc/ioctl.save +5. 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 + 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). -6. /dev/console and X +6. ``/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, + 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: + ``/dev/console instead of /dev/tty0``. Some of those programs are:: - Xfree86, svgalib, gpm, SVGATextMode + Xfree86, svgalib, gpm, SVGATextMode 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. + 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. 7. Thanks |