101 System Architecture KT Flashcards
101.1 Determine and Configure Hardware Settings
The following is a partial list of the used files, terms and utilities:
/sys/ /proc/ /dev/ modprobe lsmod lspci lsusb
/sys/
Directory that stores structured device data migrated by sysfs.
/proc/
Directory that stores unstructured info about devices and processes.
/dev/
Directory that stores device files.
modprobe
Command: Adds or Removes a module from the Linux kernel.
lsmod
Command: Displays the kernel modules loaded.
lspci
Command: Displays information about PCI bus and devices.
lsusb
Command: Displays the USB information and devices.
101.2 Boot the System
The following is a partial list of the used files, terms and utilities:
dmesg journalctl BIOS UEFI bootloader kernel initramfs init SysVinit systemd
dmesg
Command: Displays all messages from the kernel ring buffer.
journalctl
Command: used to query the contents of the systemd journal logs.
BIOS
Basic Input Output System - connects firmware to an operating system.
UEFI
Unified Extensible Firmware Interface - connects firmware to an operating system.
bootloader
Code that runs before any operating system. It usually contains several ways to boot the OS Kernel.
kernel
A computer program that makes up the core of the computer. It interfaces between the hardware and software.
initramfs
Prepares the system to load the root file system from RAM.
init
init (initialization) is the first process that is started during the booting of the system. It is the parent of all processes and continues running till the system is shutdown.
SysVinit
SysVinit is a Linux initialization system and service manager that starts processes in a serialized manner(one by one).
systemd
systemd is a Linux initialization system and service manager that includes features like parallel initialization, on-demand starting of daemons, mount and automount point maintenance, snapshot support, and processes tracking using Linux control groups. systemd provides a logging daemon and other tools and utilities to help with common system administration tasks.
101.3 Change Run Levels / Boot Targets and Shutdown or Reboot System
The following is a partial list of the used files, terms and utilities:
/etc/inittab shutdown init /etc/init.d/ telinit systemd systemctl /etc/systemd/ /usr/lib/systemd/ wall
/etc/inittab
Configuration file used by the System V (SysV) initialization system. It defines for the init process:
The defaul runlevel.
What processes to start, monitor, and restart.
What actions to take when the system enters a new runlevel.
shutdown
Command: Brings the system down in a secure way.
shutdown [OPTIONS] [TIME] [MESSAGE]
init
init (initialization) is the first process that is started during the booting of the system. It is the parent of all processes and continues running till the system is shutdown.
/etc/init.d/
/init.d directory contains start/stop scripts for services on the Linux system.
telinit
Command: telinit may be used to change the system runlevel.
telinit [OPTION]… RUNLEVEL
systemd
systemd is a Linux initialization system and service manager that includes features like parallel initialization, on-demand starting of daemons, mount and automount point maintenance, snapshot support, and processes tracking using Linux control groups. systemd provides a logging daemon and other tools and utilities to help with common system administration tasks.
systemctl
Command: systemctl is a controlling interface and inspection tool for the widely-adopted init system and service manager systemd.
systemctl [OPTIONS…] COMMAND [NAME…]
/etc/systemd/
Directory where admin configurations are stored for systemd units.
/usr/lib/systemd/
Directory where vendor/distibution supplied files and configurations are stored for systemd units.
wall
Command: (Write to all) Used to display contents of a file or standard output to all logged in users.
wall [file]
