System Startup, Runlevels and Log files

General Description

In this module we learn about the following -

The role of system administrator
Unix commands related to LPI
Hardware configuration
Boot system
run-levels and boot target

Typical Role of System Administrator

Installing and configuring servers
Installing and configuring application software
Creating and maintaining user accounts
Backup and restoring files
Configuring secure system
Using tools to monitor security
Automating repetitive tasks
Initiating or updating technical policy documentation
Maintaining awareness of security threats & patches

Boot Process

Server firmware starts and performs-

> a check of the hardware called POST (Power On Self-Test)

> looks for boot loader program

> runs Boot loader

> Linux Kernel Determined

> Kernel program loads into memory

> mounts the root partition

> initialisation program runs

> Background program runs (e.g. desktops or desktop manager, and database applications).

Boot Loader

Boot loader is a bridge between system firmware and kernel. It supports dual-boot machines which can be Linux or Window OS.

Init / Systemd

• init/ systemd is the first process that runs in a UNIX system. It has a Process ID (PID) of 1

• sys v init processes instructions from / etc/inittab

• systemd (2010+) is mostly found as it is claimed to reduce initialisation time.

systemctl utility to manage system services

systemctl COMMAND UNIT-NAME

COMMAND= disable, enable, restart, start, status, stop, reload

COMMAND= is-active, is-enabled, is-failed

UNIT NAME: firewalld , ntpd , dhcpd

Service Unit Files .service

Contains information such as which environment file to use when a service must be started, located in different directories

systemctl list-unit-files #show unit file name and state (e.g., enabled, disabled, static, etc.)

Runlevels

Runlevels in Unix-based dedicated servers are numbered 0-6. Each of these numbers has its own functions. Which defines the state of the machine after the boot of the Linux Kernel. Following table summarises the standard and reserved runlevels for Linux distributions.

Runlevel

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