Hardware Reference
In-Depth Information
console=tty1 \
root=/dev/mmcblk0p2 \
rootfstype=ext4 \
elevator=deadline \
rootwait
$
This file is provided as a convenience, since the parameters can be configured in
the
config.txt
file, using the
cmdline="text"
option. When the
config.txt
option is
provided, it supersedes the
cmdline.txt
file.
Once the Raspbian Linux kernel comes up, you can review the command-line
options used as follows (edited for readability):
$ cat /proc/cmdline
dma.dmachans=0x7f35 \
bcm2708_fb.fbwidth=656 \
bcm2708_fb.fbheight=416 \
bcm2708.boardrev=0xf \
bcm2708.serial=0xf52b69e9 \
smsc95xx.macaddr=B8:27:EB:2B:69:E9 \
sdhci−bcm2708.emmc_clock_freq=100000000 \
vc_mem.mem_base=0x1c000000 \
vc_mem. mem_size=0x20000000 \
dwc_otg.lpm_enable=0 \
console=ttyAMA0,115200 \
kgdboc=ttyAMA0,115200 \
console=tty1 \
root=/dev/mmcblk0p2 \
rootfstype=ext4 \
elevator=deadline \
rootwait
$
Additional options can be seen prepended to what was provided in the
cmdline.txt
file. Options of the format
name.option=values
are specific to kernel-loadable modules.
For example, the parameter
bcm2708_fb.fbwidth=656
pertains to the module
bcm2708_fb
.
There are too many Linux kernel parameters to describe here (entire topics have
been written on this topic), but some of the most commonly used ones are covered in the
following subsections.
Serial console=
The Linux console parameter specifies to Linux what device to use for a console. For the
Raspberry Pi, this is normally specified as follows:
console=ttyAMA0,115200
