Tell about 'console=null|""' and how to use it.
It can be helpful to set (enable) CONFIG_NULL_TTY so that the ttynull
driver is available. This avoids problems with stdin/stdout/stderr of
the init process. Howevere, CONFIG_NULL_TTY cannot be enabled by default
because it can be used by mistake [see commit a91bd6223ecd ("Revert
"init/console: Use ttynull as a fallback when there is no console").]
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: John Ogness <john.ogness@xxxxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
---
v2: "must be the only console=" instead of the first one. (Petr)
Add info about CONFIG_NULL_TTY to the commit message. (Petr)
Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
1 file changed, 6 insertions(+)
--- linux-next-20220216.orig/Documentation/admin-guide/kernel-parameters.txt
+++ linux-next-20220216/Documentation/admin-guide/kernel-parameters.txt
@@ -724,6 +724,12 @@
hvc<n> Use the hypervisor console device <n>. This is for
both Xen and PowerPC hypervisors.
+ { null | "" }
+ Use to disable console output, i.e., to have kernel
+ console messages discarded.
+ This must be only console= string used on the
+ kernel command line.
+
If the device connected to the port is not a TTY but a braille
device, prepend "brl," before the device type, for instance
console=brl,ttyS0
