Linux sysadmin tutorials linux system administrator

 Files and Directories Management
 User and Group Administration
 Basic File Permissions
 Disk Partitioning and Mounting File System
 Data Backup and Recovery
 Software Package Administration
 Dynamic Host Configuration Protocol (DHCP)
 FTP Server (vsftpd daemon)
 DNS Server
 Web Server (Apache)
 Network File System (NFS)

nano

Vim

touch

tee

directory level operations

file permissions

644

r read

W write

X execute

change owner chown

Ownership

Owner, group, public

change group

chgrp

User management

users

group

Permission

system accounts

interactive accounts

sudo add user newuser;

m- creates directory for user, if not exist.

M- not creates directory for user

add /change password to user

passwd newuser;

groupadd newgroup;

creates new group.

gpasswd new group:

New password

re enter password

groups; to view all groups

groups group name

To view users in group

chgrp file/directory ownership to other group.

usermod

add & remove users from group

-a adds user to group only -G option

-G adds removes users to secondary groups

-g primary group

-d directory users directory

usermod -a -G group user

backup fstab

backup grub file

edit files

Save

add quota to user, group

Remount & restart

systemd  used to manage both services and daemons

systemctl –version

systemd 230

Units are the resources systemd knows how to interpret

12types

/lib/systemd/system (base unit files)

/etc/systemd/system (modified unit files at runtime)

-t service or sockets

-a loaded units

systemctl -t service

systemctl stop apache2

systemctl –all -t service | grep apache2

Start/stop/reload/restart/enable/disable/status

systemctl status network.service

systemctl is the utility used to control systemd

systemctl status

all status

systemctl status firewalld

Ufw iptables

systemctl list-units –type=socket

systemctl list-units –type=service

systemctl cat firewalld

Cat to read/write append etc.

cgroups or Control Groups

used assign resources for groups and users by admin

cpu,disk, memory,

Install & enable libcgroup

yum install libcgroup

systemctl enable cgconfig

Process Management–bg, fg, nohup, ps, pstree, top, kill, killall, free, uptime, nice.

PID= process identification number

Pgrep used to know pid of process.

pgrep systemd

1

jobs − List of the current processes attached to the shell

ctrl+z to. sleep the current process.

ps command

ps axw | grep python

ps= process snapshot

grep : to filter the process name

a= Excludes constraints of only the reporting processes for the current user

X=Shows processes not attached to a tty or shell

W= Formats wide output display of the output

-u= shows all processes by specific user

-c all process by name or PID

-e selects all processes

–sort

to see all processs by user

ps -u www-data

all information about the process nginx

ps -wl -C nginx

top 10 memory consuming process

top,htop

Or

ps aux –sort =-pmem | head -10

pstree

tree like model

killall

killall chrome

kills all the process for all users.

pkill: kill the process by name

pgrep apache2

to know process id

pkill -9 apache2

Kill command

Kill pid

Signals graceful kill

SIGTERM

firewalld in centos

iptables /, ufw in ubuntu debian Linux distributions

block ports,

block services,

block ipmasq

ICMP (Internet Control Message Protocol)

Block ip addresses

firewalld & ufw uses  iptables as a backend.

ssh client (putty), sftp client (winscp).

whm, capnel, zpanel etc.

components behind systemd logging are: journald(daemon), journalctl(analyzes events logged by journald), and journald.conf(config file)

journalctl −k (kernel messages)

journalctl −u (units like services, sockets,sshd,apache2)

logs by type emergency,warn

0-emergency

1 alert

2 critical

3 error

4 warning

5 info

6 debug

journalctl -p 4

Warning logs.

321 rule

3 copies of data.(working data, backup on server weekly, offline in hdd)

rsync remote sync

rsync syntax:rsync [options] [local path] [[remote host:remote path] or [target path

or use sftp client to download compress data.

 Syncing backup in local & remote

local

mkdir /root/etc_baks

rsync -aAvr /etc/ /root/etc_baks/

system updates & install update packages

linux disruption upgrade

sudo apt-get update && sudo apt-get upgrade

Installing packages or additional softwares

add dependency or repository

To install precompiled softwares for your linux distribution.

or manually downloading & compile & install.

sudo apt-get remove curl

autoclean options are there.

Shell scripting

a bit knowledge of programming required.

Like logical operators, variables, condition statements, & loops .

physical disk = dev/ sda

partition physical disk  dev / sda1 dev/sda2

Volume group (group of physical volume by physical disks) 2disk each 1tb in a sysyem 2tb is the volume group.

Logical volume

LVM tools such as the System Storage Manager: lsblk, parted, and mkfs.xfs.

lsblk is a great tool for getting disk information

disks on this system: sda, sdb, and sdc.

sda has linux so,

parted /dev/sdb mklabel GPT

all data will ve deleted

parted -a opt /dev/sdb mkpart primary ext4 0% 100%

any warnings

Update fstab

/etc/fstab

Make files system

(Which linux file system useful for you)

xfs filesystem

mkfs.xfs -f /dev/sdb1

Lets verify

lsblk -o NAME,FSTYPE

Mounting

mount -o defaults /dev/sdb1 /mnt/sdb

mount on boot we need to edit fstab.

Or ssm

apt install system-storage-manager

ssm list

To know the volumes

create -p NEW_POOL /dev/sdb1 /dev/sdc1

One large disk from freespace

or 3seperateeach 3.3gb out of 10gb.

root@localhost rdc]# ssm create -n disk001 –fs xfs -s 3GB -p NEW_POOL

• History of UNIX and LINUX
• Differences between CentOS, Red Hat
Enterprise Linux & Fedora
• FHS and Linux Installation
Files and Directories Management
• Creating files using cat and touch
commands
• Creating directories using mkdir
command
• Modifying file content using vi / vim
editors
User and Group Administration
• Creating and deleting users from the
systems
• Creating and deleting groups
Basic File Permissions
• Verifying file permissions of existing
objects
• Modifying files permissions using chmod
command
Disk Partitioning and Mounting File
System
• Creating partition using fdisk command
• Formatting the partitions
• Mounting the partitions
Data Backup and Recovery
• Taking data backup using tar command
Software Package Administration
• Installing and deleting software packages
using RPM & YUM
• Querying and updating software
packages
Dynamic Host Configuration Protocol
(DHCP)
• Configuring Linux as DHCP Server
• Configuring various clients for DHCP
Server (Windows & Linux)
FTP Server (vsftpd daemon)
• Basics of File Transfer Protocol
• Configuring FTP protocol to download
and upload the files
DNS Server
• Configuration of DNS server
• Configuration of forward lookup zone
• Configuration of reverse lookup zone
• Testing tool of DNS zones
Web Server (Apache)
• Basics of Web Service
• Introduction to Apache
• Configuring Apache to host website
Network File System (NFS)
• Configuring NFS file sharing server
• Mounting NFS shared folder from client
systems