Disable clearing of boot messages

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Revision as of 15:32, 25 October 2012 by Grawity (talk | contribs) (Using flow control: Added note)
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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 dmesg or all logs from the current boot with journalctl -b.

Using flow control

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

Note: This pauses not only the output, but also programs which try to print to the terminal, since they'll block on the write() calls for as long as the output is paused. If your init appears frozen, make sure the system console is not paused.

Have boot messages stay on tty1

By default, arch has the getty@tty1 service enabled. The service file already passes --noclear, which stops agetty from clearing the screen. However systemd clears the screen before starting it because the unit file uses TTYVTDisallocate=yes. To disable this:

# sed /TTYVTDisallocate=/s/yes/no/ < /usr/lib/systemd/system/getty@.service > /etc/systemd/system/getty@tty1.service

Disable clearing in /etc/issue

Disable displaying of /etc/issue

Edit /etc/systemd/system/getty@tty1.service (which should no longer be a symlink):

ExecStart=-/sbin/agetty --noclear --noissue %I 38400

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

Add the file to /etc/systemd/system/getty@tty1.service's ExecStart line with the -f switch:

ExecStart=-/sbin/agetty --noclear %I 38400 -f /etc/issue.tty1