/proc/cmdline

This file shows the parameters passed to the kernel at the time it is started. A sample /proc/cmdline file looks like the following: 

ro root=/dev/VolGroup00/LogVol00 rhgb quiet 3

This output tells us the following:

ro

The root device is mounted read-only at boot time. The presence of ro on the kernel boot line overrides any instances of rw.

root=/dev/VolGroup00/LogVol00

This tells us on which disk device or, in this case, on which logical volume, the root filesystem image is located. With our sample /proc/cmdline output, the root filesystem image is located on the first logical volume (LogVol00) of the first LVM volume group (VolGroup00). On a system not using Logical Volume Management, the root file system might be located on /dev/sda1 or /dev/sda2, meaning on either the first or second partition of the first SCSI or SATA disk drive, depending on whether we have a separate (preceding) boot or swap partition on that drive.

For more information on LVM used in Community Enterprise Linux, refer to .

rhgb

A short lowercase acronym that stands for CentOS Graphical Boot, providing "rhgb" on the kernel command line signals that graphical booting is supported, assuming that /etc/inittab shows that the default runlevel is set to 5 with a line like this: 

id:5:initdefault:
quiet

Indicates that all verbose kernel messages except those which are extremely serious should be suppressed at boot time.