Linux Kernel in a Nutshell

Name

earlyprintk — Show early boot messages.

Synopsis

earlyprintk=[vga|serial][,ttyS n[,baudrate]][,keep]

Show kernel log messages that precede the initialization of the traditional console. These messages are typically never seen on the console unless you use this option. Enabling this can be very useful for tracking down hardware issues. Currently, the option can specify either the VGA device or the serial port, but not both at the same time. Also, only the ttyS0 or ttyS1 serial devices will work. Interaction with the standard serial driver is not very good, and the VGA output will eventually be overwritten by the real console.

Append ,keep in order not to disable the messages shown by this option when the real kernel console is initialized and takes over the system.