boot sequence Flashcards
traditional utility used for viewing kernel ring buffer
dmesg
systemd utility to view the kernel ring buffer within the systemd journal
journalctl -k
On most modern Linux distributions is used instead of the old init system. And with it comes a command called journalctl
systemd
logs every event that goes on within the computer part of those events that gets logged to the journal are also kernel messages such as what we see here
with the D message command.
journalctl
Typically, you will use the kernel ring buffer to take a look
to see if hardware is getting recognized by the Linux Kernel but it may not be recognized by programs such as udev or show up in a /dev directory.
details on the hardware that the kernel can see and how it activates it along with a whole lot of really low level memory management messages that can pop up when the kernel deals with RAM. legacy method that was used to actually pull up information about the kernel ring buffer.
dmesg
Which is an area of RAM that the kernel writes all of its system messages to.
Kernel Ring Buffer
Meaning that once the computer reboots these logs are gone and we start all over again.
Volitile
which are logs that are generated when the computer itself boots up and they are volatile
Boot Logs
After a computer starts the bios on the motherboard checks on all of the hardware and input and output devices. Once everything checks out
the boot process for the computer can begin.
Linux boot process.
GRUB - Grand Unified Boot Loader
legacy
look for the section of the hard drive that contains the data needed to boot an operating system and load the Linux Kernel.
boot program
will then load what is called an initial RAM disk which contains a bunch of device drivers and starts to load the computer’s drivers to eventually mount the file system from the hard disk.
The Linux Kernel
After the kernel is all set up and ready to go
it then starts off the initialization system.
is to process input and output that it is given regardless of where it comes from
and interact with the computer’s hardware.
The kernel’s main focus