Difference between revisions of "Disable clearing of boot messages"

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(Have boot messages stay on tty1: make KMS/scrollback a note)
(Have boot messages stay on tty1: moved to getty)
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{{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.}}
 
{{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 {{ic|getty@tty1}} service enabled. The service file already passes {{ic|--noclear}}, which stops agetty from clearing the screen. However [[systemd]] clears the screen before starting it. To disable this behavior, create a drop-in directory {{ic|/etc/systemd/system/getty@tty1.service.d/}} and create a {{ic|noclear.conf}} file in it:
 
{{hc|1=/etc/systemd/system/getty@tty1.service.d/noclear.conf|2=
 
[Service]
 
TTYVTDisallocate=no
 
}}
 
 
This overrides only {{ic|TTYVTDisallocate}} for agetty on TTY1 and let the global service file {{ic|/usr/lib/systemd/system/getty@.service}} untouched. This is the recommended way to [[Systemd#Editing provided units|edit systemd unit files]].
 
 
{{Note|
 
* Late KMS starting may still cause the first few boot messages to clear. If this is the case, try enabling [[KMS#Early KMS start|early KMS start]].
 
* There will probably be too many boot messages to view on one screen. Use Shift+PgUp/PgDown to scroll. If there are too many boot messages you still might not be able to see all of them by scrolling. Try increasing the size of your [[scrollback buffer]].
 
}}
 

Revision as of 15:31, 22 August 2016

Merge-arrows-2.pngThis article or section is a candidate for merging with getty.Merge-arrows-2.png

Notes: Most information on this page is about modifying the agetty service (Discuss in Talk:Disable clearing of boot messages#)

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):

  • Press Ctrl+S to pause the output
  • And Ctrl+Q to resume it
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.