Disable clearing of boot messages

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Revision as of 13:03, 17 September 2011 by Solstice (talk | contribs) (Using flow control: new change in agetty)
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After the boot process, the screen is cleared and the login prompt appears, leaving users unable to read init output and error messages. This default behavior may be modified using methods outlined in this article.

Note that regardless of the chosen option, kernel messages can be displayed for inspection after booting by using Template:Codeline.

Note: Given the recent change in agetty, the mandotory change is: add a --noclear option to the call of agetty in /etc/inittab and also remove /etc/issue first line. See below

Using flow control

This is basic management that applies to most terminal emulators, including virtual consoles (vc):

More permanent solution

For a more permanent change, the following can be used to add a pause, or wait for keypress while boot messages are still on the screen:

  • Wait for a keypress before clearing the screen:
 read -n1
  • Wait for at most 5 seconds or until a keypress occurs:
 read -t5 -n1

Add one of these to either the bottom of Template:Filename to pause when booting is finished, or the stat_fail() function in Template:Filename to pause when a boot script in /etc/rc.d fails with an explicit error code. Note that the latter is a system script and may be overwritten when that file is updated. If you are unsure what this means, use Template:Filename.

Have boot messages stay on tty1

Normal behaviour: Boot messages shoot past, screen is cleared, contents of Template:Filename are displayed, login (either CLI or login manager) is displayed.

Desired behaviour: Boot messages shoot past, login (either CLI or login manager) is displayed without clearing of tty1

There are three methods to achieve this. Choose the one that suits you best.

Method 1: edit /etc/inittab

If the default getty, Agetty, is used, it is possible to skip displaying the contents of Template:Filename altogether and instead keep the boot messages displayed on tty1. In Template:Filename, you will find a list of numbered consoles which look something like the following; just scroll down in the file to find it. Then you need to add the Template:Codeline option for the first virtual console (the c1 line) only:

c1:2345:respawn:/sbin/agetty -i -8 38400 tty1 linux
c2:2345:respawn:/sbin/agetty -8 38400 tty2 linux
.
.
.

Alternatively simply comment the first line. Note: this way the login dialogue does not appear, i.e. tty1 is locked.

#c1:2345:respawn:/sbin/agetty -8 38400 tty1 linux                                                                                                              
c2:2345:respawn:/sbin/agetty -8 38400 tty2 linux                                                                                                               
.
.
.

But if you are using mingetty, you will need to add the Template:Codeline and Template:Codeline options for your first virtual console (c1) only:

c1:2345:respawn:/sbin/mingetty --noclear --noissue tty1 linux
c2:2345:respawn:/sbin/mingetty tty2 linux
.
.

Method 2: give tty1 a custom /etc/issue

Copy the existing /etc/issue file to /etc/issue.tty1 (without the first line):

sed 1d /etc/issue > /etc/issue.tty1

Find this in /etc/inittab:

c1:2345:respawn:/sbin/agetty -8 38400 tty1 linux

Replace it with:

c1:2345:respawn:/sbin/agetty -8 38400 tty1 linux -f /etc/issue.tty1

Method 3: edit /etc/issue directly

Simply cut the contents of the first line in /etc/issue so it looks like this:

Arch Linux \r  (\n) (\l)
Warning: Read below how to restore the file before attempting this.

Restoring /etc/issue

The characters cannot be just typed again into the file because they are special characters not available on your keyboard!

After you cut the contents from line 1 in Template:Filename, paste it into a temporary file somewhere on you computer so you can copy and paste it back into Template:Filename later when you wish to restore original functionality. You can also backup the whole Template:Filename somewhere safe and restore it when needed.

Optionally, if you are more advanced, you can follow special procidures for typing in these special characters:

Methods of placing literal escape characters are editor dependent. In Vim:

ESC (exit insert mode)
:r !clear
:x (Save and Exit)

This will insert the literal characters equivalent to the shell Template:Codeline command. Optionally you can also insert the characters manually:

i (insert)
ctrl-v (insert literal character)
ESC (insert escape character)
c
ESC (exit insert mode)
ZZ (Save and Exit)

In Emacs:

C-q ESC (to insert literal escape)

See Also