hostnamectl set-hostname <hostname>

set hostname

timedatectl

show timedate info

timedatectl list-timezones

list all timezones

timedatectl set-timezone Australia/Sydney

set timezone to Sydney

timedatectl set-ntp true

chronyd

service used for time synchronisation

/etc/chronyd.conf

config file

/var/log/chrony

log file

systemctl start/restart chronyd

start/restart chronyd service

chronyc

program command

rpm -qa | grep chrony

verify it is installed

ps -ef | grep chrony

verify it is running

yum install chrony

if it is not installed

sudo dnf repolist

check which repositories are installed

subscription-manager repos --enable codeready-builder-for-rhel-10-x86_64-rpms

enable codeready linux builder repository

dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-10.noarch.rpm

install EPEL

sudo dnf install --nogpgcheck https://mirrors.rpmfusion.org/free/el/rpmfusion-free-release-$(rpm -E %rhel).noarch.rpm https://mirrors.rpmfusion.org/nonfree/el/rpmfusion-nonfree-release-$(rpm -E %rhel).noarch.rpm

install rpmfusion

ssh-keygen

generate the key

ssh-copy-id root@192.168.1.X

copy the key to the host

ssh root @192.168.1.X

login to remote host

ssh -1 root 192.168.1.X

Linux Filesystems:
ext3

ext4

xfs

Windows Filesystems:
NTFS
FAT

pwd

print working directory

cd

home directory (/home/username) or /root

~

/

root directory (absolute)

~

user directory (/home/username)

.

current directory (relative)

..

parent directory (relative)

ls

show directory contents

ls -l

show directory contents (list view)

ls -ltriah

show directory contents (list view)

-l long

-t time sorted (-S for size sorted)

-r reverse

-i inode

-a show hidden files

-h human readable file sizes

Type

# of Links

User Owner

Group Owner

Size

Month

Day

Time

Namedrwxr-xr-x

drwxr-xr-x

21

root

root

4096

Feb

27

13:33

var

lrwxrwxrwx

1

root

root

7

Feb

27

13:15

bin

-rw-r--r--

1

root

root

0

Mar

2

11:15

testfile

d

directory

l

link

file

touch filename

create file

rm filename

remove file

cp filename newfilename

copy file and name it

cp filename /tmp

copy file to /tmp

mv filename newfilename

renames the file

mv filename /tmp

move file to /tmp

mkdir dirname

create directory

rmdir dirname

remove directory

rm -r dirname

remove directory

chgrp groupowner filename

change the group owner of a file

chown userowner filename

change the user owner of a file

chown userowner:groupowner filename

change the user and group owner of a file

echo "text" > filename

insert the text into the file

cat filename

display the text inside a file

rm -rf

remove directory (recursive) (force)

nsotelo@rhel-pc:~$ find / -name "*ksh*.rpm" 2> /dev/null

search file or directory names for items containing name ksh and ending with .rpm

stderr to /dev/null

grep -ri error /var/log/ 2> /dev/null | wc -l

search file contents for key words

-c count

-r recursive

-i ignore case sensitive

-n display matched lines and their line numbers

-v all except specified

wc -l word count lines only

egrep -i "keyword|keyword2" /var/log

search file contents for two key words

find /etc -name "*.conf*" | xargs grep "localhost"

combination of above commands (output of find translated and input to grep

ln /location/file

creates a hard link to a file

ln -s /location/file

creates a soft link to a file

standard input (stdin) with file descriptor 0

ls >> listings

appends the output of ls to listings file

standard output (stdout) with file descriptor 1

cat < listings

feeds file contents to a file

standard output (stdout) with file descriptor 1

mail -s "office memo" allusers@abc.com < memoletter

feeds file contents to a file

standard error (stderr) with file descriptor 2

ls -l /root 2> errorfile

outputs the error message to errorfile

ed (1969)

original, line oriented standard for  Unix

ex (1976)

extended, more powerful version of ed, introduced visual mode for full screen editing

vi (1976)

classic, efficient, visual full-screen editor built on top of ex

emacs (1976)

extensible, feature-rich ecosystem known for customisation

pico (1992)

simple, menu-driven, for non-technical users

vim (1991)

improved and advanced version of vi, with modern features

nano (1999)

free open source clone of pico

echo 'export EDITOR=nano' >> ~/.bashrc

set nano as default text editor

mode

command

function

esc

up

down

left

right

move around

esc

shift g

move to end

esc

i

insert

insert

a

move right (and insert)

insert

o

line break (and insert)

insert

esc

escape current mode

esc

x

remove character

esc

r

replace character

esc

d

delete line

esc

u

bring line back

esc

:q!

quit

esc

:wq!

save and quit

ctrl o

save current file (write out)

ctrl s

save current file (newer versions)

ctrl x

exit

ctrl w

search for specific text

ctrl \

find and replace

ctrl k

cut line

ctrl u

paste line

alt 6

copy line

alt n

toggle line numbers

alt u

undo

alt e

re-do

echo $0

display current shell

cat /etc/shells

display available shells

cat /etc/passwd

shows user's shell e.g. /bin/bash)

chmod a+x scriptname

allow execute permission for all

./script.bash

execute from current location

/home/userdir/script.bash

execute from absolute location

#!/bin/bash

Shell

# This script does X

Comment

echo/cp/grep

Command

if/while/for

Statement

#!/bin/bash

# made by Nicolas Sotelo

whoami

echo

pwd

echo

hostname

echo

ls -ltr

echo

shell

comment

command

space

#!/bin/bash

a=Nicolas

b=Sotelo

c="Linux Class"

echo "My first name is $a"

echo "My surname is $b"

echo "My class is $c"

set variable


echo variable

#!/bin/bash
echo Hello, my name is Nicolas Sotelo

echo

echo What is your name?

read namevar

echo

echo Hello $namevar

echo

read sets variable to the user's input

echo variable

#!/bin/bash
hnvar=`hostname`
echo Hello, my hostname is $hnvar
echo

echo What is your name?

read namevar

echo

echo Hello $namevar

echo

set variable as a `command`
echo the output

#!/bin/bash
count=100

if [ $count -eq 100 ]

then

echo Count is 100

else

echo Count is not 100

fi

end if statement

#!/bin/bash
 

clear

if [ -e /home/nsotelo/error.txt ]

then

echo "File exists"

else

echo "File does not exist"

fi

#!/bin/bash

clear

echo

echo "What is your name?"

echo

read namevar

echo

echo Hello $namevar sir

echo

echo "Do you like working in IT? (y/n)"

read Like

echo

if [ "$Like" == "y" ]

then

echo "You are cool"

elif [ "$Like" == "n" ]

then

echo "You should try IT, it's a good field"

echo

fi

#!/bin/bash
for numv in 1 2 3 4 5

do

echo "Welcome $numv times"

done

assign 1 2 3 4 5 to numv

repeatedly display for each of the specified variables

#!/bin/bash

for actionv in eat run jump play

do

echo "See Nick $actionv"

done

assign eat run jump play to actionv

repeatedly display for each of the specified variables

#!/bin/bash

for filev in {1..5}

do

touch $filev

done

for loop to create 5 files named 1-5

#!/bin/bash

for filev in {1..5}

do

rm $filev

done

for loop to delete 5 files named 1-5

#!/bin/bash

i=1

for day in Mon Tue Wed Thu Fri

do

echo "Weekday $((i++)): $day"

done

specify days in for loop

#!/bin/bash

a=1

for username in `awk -F: '{print $1}' /etc/passwd`

do

echo "Username $((a++)) : $username"

done

list all users one by one from /etc/passwd file

crontab -e

scheduled jobs
-e edit

at.

scheduled one-off jobs

* * * * *

minute  (0-59), hour (0-23), day (1-31), month (1-12), week day (0-6)
 

0 * * * * /home/user/script

run every hour (at minute 0)

0 0 * * * /home/user/script

run every day (at midnight)

30 4 * * 1 /home/user/script

run every Monday at 4:30 AM

d

r

w

x

r

w

x

r

w

x

file

type

user

read

user

write

user

execute

group

read

group

write

group

execute

others

read

others

write

others

execute

chmod u+rw filename

user owner add rw

chomd g-w filename

group owner remove w

chmod o+r filename

others owner add r

chmod a-r filename

all owners remove r

chmod 755 filename

set to rwxr-xr-x

chmod 644 filename

set to rw-r--r--

chmod 777 filename

set to rwxrwxrwx

chown root filename

change user owner to root

chgrp root filename

change group owner to root

getfacl

get file acl

setfacl -m u:user:rwx filename

add permissions for user

setfacl -m g:group:rw filename

add permissions for group

setfacl -rm  u:user:rwx dirname

add permissions for directory
-r recursive

setfacl -x u:user filename

remove entry for user

setfacl -b filename

remove all entries

useradd username

create a user

groupadd groupname

create a group

userdel username

delete user

groupdel groupname

delete group

usermod username

modify user

cat /etc/passwd

display users, passwords (x=encrypted), UserID, GroupID, etc.

-d

(lastchanged) days since 01/01/1970 that password was last changed

-m

minimum number of days between password changes

-M

maximum number of days before user must change password

-W

number of days before password is to expire before user is warned

-I

number of days after password expires that account is disabled

-E

days since 01/01/1970 that account is disabled (account end date)

su -

switch to root

su - username

switch user

sudo

perform action as super user

visudo

su -

switch to root

usermod -aG wheel nsotelo

adds nsotelo to wheel group

grep wheel /etc/group

verify

su - nsotelo

switch back to nsotelo

sudo fdisk -l

run sudo command to confirm access

command

example

function

fdisk

fdisk -l

disk partitioner

-l list disks

df

df -h

filesystem capacity

du

du -sh /var/log

size of each item in directory

uptime

uptime -p

shows urrent time, uptime and load usage % past 1, 5, 15 minutes

top

top -h

display linux processes (human readable)

free

free -h

display amount of free and used system memory (human readable)

lsof

lsof -I :80

list open files (using port 80)

tcpdump

tcpdump -i eth0

capture packets flowing through interface eth0

ps

ps -ef --forest

current processes snapshot (tree diagram)

kill

kill 34448

terminates a process (PID)

PID

USER

PR

NI

VIRT

RES

SHR

S

%CPU

%MEM

TIME+

COMMAND

PID

id

USER

owner

PR

focus priority

NI

the nice value

VIRT

amount of virtual memory in use

RES

amount of resident memory in use

SHR

amount of shared memory in use

S

status of the process

%CPU

share of CPU time since last update

%MEM

share of physical memory in use

TIME+

total cpu time used (hundredths of a second)

COMMAND

name of the command or process

systemctl --version

Check if systemd is installed

ps -ef | grep system

check if systemd is running

systemctl --all

check all running services

systemctl status/stop/start/restart application.service

status/start/stop/restart application.service

systemctl reload application.service

reload the config of a service

systemctl enable/disable application.service

enable or disable at boot

systemctl mask/unmask application.service

enable or disable completely (ignore dependencies)

/var/log

log directory

sos report

collect logs and configuration file then transfer to Redhat support server
enter case ID
compressed archive saved to /var/tmp/sosreport-hostname-caseid-yyyy-mm-dd-filename.tar.xz

cockpit

web based server administration tool sponsored by Red Hat

can monitor system resources, add/remove accounts, shutdown system and perform other tasks

also available centos redhat ubuntu fedora

ping www.google.com

verify internet connectivity

rpm -qa | grep cockpit

verify cockpit package is installed

yum/dnf install cockpit -y

install cockpit (Red Hat, CentOS)

apt-get install cockpit

install cockpit (Debian, Ubuntu)

systemctl start/enable cockpit.socket

relies on socket activation to start
enable socket listener which watches port 9090 and wakes Cockpit up when someone tries to connect

systemctl status cockpit

verify

systemctl status cockpit.socket

verify

https://192.168.50.164:9090

firewall may need to be disabled (safe for labs) or rule created
access the web-interface

log in with root or system user

can be used to manage everything including terminal access

rpm -qa | grep tuned

check if tuned package is installed

yum install tuned

install tuned

systemctl status/enable/disable tuned

check tuned status

tuned --version

check tuned version

tuned-adm

change setting for tuned daemon

tuned-adm active

check which profile is active

tuned-adm list

list available profiles

tuned-adm profile profile-name

change profile

tuned-adm recommend

recommended profile

tuned-adm off

turn off tuned daemon

https://192.168.X.X:9090

change via web console (check firewall)

top

check active process priority
PR = System priority (-99 to 39)
NI = nice value (-20 to 19)

ps axo pid,comm,nice,cls --sort=-nice

show active processes nice, by nice

nice -n # process-name

set process value

nice -n -12 top

set top nice to -12

renice -n -15 <PID>

change active PID nice to -15
(open 2nd terminal to check)

ip a

Display network inerfaces and details

ip addr

ifconfig

hostnamectl set-hostname <hostname>

set hostname

systemctl status NetworkManager

NetworkManager status

ps -ef | grep NetworkManager

verify the process is running

nmcli

network manager cli (non gui) can be used in scripts

nmtui

text user interface

nm-connection-editor

full gui (via desktop/console)

GNOME Settings

nmcli connection

connected interface UUIDs

nmcli device

connected interface status

nmcli connection modify eth0 ipv4.addresses 192.168.50.X/24

set static ip address & subnet mask

nmcli connection modify eth0 ipp4.gateway 192.168.50.1

set gateway

nmcli connection modify eth0 ipv4.method manual

configure eth0 to use static IP

nmcli connection modify eth0 ipv4.dns 8.8.8.8

set dns to google.com

nmcli connection down eth0 && nmcli connection up eth0

restart nmcli connection

ip address show eth0

nmcli device status

nmcli connection show --active

ifconfig

nmcli connection modify eth0 +ipv4.addresses 192.168.50.X/24

set secondary static ip address & subnet mask

nmcli connection reload

systemctl reboot

ip address show

/etc/sysconfig/network-scripts

/etc/hosts

/etc/hostname

/etc/resolv.conf

DNS

/etc/nsswitch.conf

Set to use Files or DNS first (per command/request)

ping

verify network connectivity to a host

ifconfig

Display network interfaces and IP addresses

ip addr

ip a

ifup

brings up a specific network interface

ifdown

takes down a specific network interface

traceroute

track and display path (router/hops) that packets take to reach a destination host

tcpdump -i eth0

capture and monitor live network traffic flowing through eth0

nslookup

queries DNS servers to find ip adddress of a domain or vice versa

dig

ethtool eth0

display and modify physical hardware settings of eth0 such as link speed & duplex

dnf install firewalld

install firewalld

systemctl enable --now firewalld

enable now

systemctl status firewalld

details & uptime

firewall-cmd --state

status

firewall-cmd --get-active-zones

firewall-cmd --get-zones

list predefined zone profiles

• public - locked down default
• home/work - more relaxed (known networks)
• trusted - allow all
• dmz/external - edge scenarios

firewall-cmd --list-all

shows all zones, rules, services, etc.
(only a few enabled by default)

firewall-cmd --get-services

list of all services that can be allowed

firewall-cmd --reload

write permanent and custom rules to memory

firewall-cmd --add-service=http

add http (temporary)

firewall-cmd --permenent --add-service=http

add http (permanent)

firewall-cmd --remove-service=http

remove http (temporary)

firewall-cmd --permanent --remove-service=http

remove http (permanent)

firewall-cmd --add-port=1110/tcp

add TCP 1110 (temporary)

firewall-cmd --permanent --add-port=1110/tcp

add TCP 1110 (permanent)

firewall-cmd --remove-port=1110/tcp

remove TCP 1110 (temporary)

firewall-cmd --permanent --remove-port=1110/tcp

remove TCP 1110 (permanent)

firewall-cmd --add-rich-rule='rule family="ipv4" source address="192.168.0.25" reject'

block incoming packets from specific IP

firewall-cmd --remove-rich-rule='rule family="ipv4" source address="192.168.0.25" reject'

remove

firewall-cmd --add-icmp-block=echo-request

block icmp (ping) requests

firewall-cmd --remove-icmp-block=echo-request

remove

firewall-cmd --direct --add-rule ipv4 filter OUTPUT 0 -d 203.0.113.10 -j DROP

block outgoing packets to IP (priority)

firewall-cmd --direct --remove-rule ipv4 filter OUTPUT 0 -d 203.0.113.10 -j DROP

remove

nano /etc/firewalld/services/sap.xml
 

xml version="1.0" encoding="utf-8"
<service version=1.0">
    <short>SAP</short>

      <description>Third-party application service</description>

        <port protocol="tcp" port="3200"/>

  </service>

add a custom service definition for SAP

xml header for firewalld

firewall-cmd --get-services | grep -i sap

verify

firewall-cmd --add-service=sap

add the custom rule (temporary)

firewall-cmd --permanent --add-service=sap

add the custom rule (permanent)

dnf install -y httpd

install apache web service

systemctl enable --now httpd

curl -I http://localhost

verify (403 Forbidden)

curl -I http://192.168.50.164/

verify (403 Forbidden)

tar cvf nsotelo.tar /home/nsotelo

archive all folders in /home/nsotelo

mkdir new

create a directory 'new'

mv nsotelo.tar new

move archive to 'new'

cd new

change to 'new' directory

gzip nsotelo.tar

compress nsotelo.tar

gzip -d nsotelo.tar.gz

uncompress nsotelo.tar.gz

tar xvf nsotelo.tar

extract archive

rpm -qa | grep ftp

check if the required package is installed

ping www.google.com

verify internet connection

yum install vsftpd

install the remote package

nano /etc/vsftpd

disable anonymous login

uncomment ascii_upload_enable=YES

uncomment ascii_download_enable=YES

ftpd_banner=Welcome to blah FTP sevice

add to the end of the file "use_localtime=YES"

save & exit

systemctl start vsftpd

systemctl enable vsftpd

systemctl stop firewalld

systemctl disable firewalld

yum install ftp

install the client package

ftp 192.168.50.105

log in to the remote host via ftp

enter username and password of an active remote host account

bi

switch to binary mode (data integrity)

hash

display progress visually

put filename

transfer a file

bye

exit ftp

touch filename

create a file

scp filename jsmith@192.168.50.105:/home/jsmith

securely copy the file to /home/jsmith on remote host
enter jsmith password

rhc connect -u username -p password

connects to red hat subscription manager

dnf

install CentOS & RHEL packages (formerly yum)

dnf install chrony -y

install time sync manager (yes to prompts)

dnf install httpd -y

install apache web server

rpm -qa | wc -l

count how many packages are installed
-q query
-a all

wc word count

-l lines

dnf install bind

installs Berkeley Internet Name Domain package

cat /etc/redhat-release

check RHEL version

dnf update -y

update all packages to latest version

dnf install ksh -y

install kornshell package

dnf remove ksh -y

remove kornshell package

wget <download link address>

rpmfind.net

find / -name *ksh*.rpm 2>/dev/null

verifies downloaded package

rpm -ihv ksh*.rpm

KSH… package

-i install

-h progress bar

-v verbose

wget <download link for chkconfig depdency>

rpm -ihv chkconfig*.rpm

install depdedency first

rpm -qa | grep ksh

verify installation
-q query

-a all

rpm -qi ksh

more info on the package

rpm -e ksh

remove it manually

wget -O ~/iso-downloads/centos-9.iso <.iso url>

download the iso to ~/iso-downloads and name it centos-9.iso

mkdir -p /mnt/rhel-dvd

create the mount folder

-p create parent if required, suppress errors if already exists

mount -t iso9660 -o loop,ro ~/iso-downloads/centos-9.iso /mnt/rhel-dvd

mount centos-9.iso as /mnt/rhel-dvd

-t (optional) iso9660 type = standard format for optical disks

-o loop - option to treat the iso as a physical block device

ro read only

df -h

verify mounted disk file system
-h human readable

mkdir -p /localrepo

create a directory for .rpm packages and metadata

cp -rv /mnt/rhel-dvd/BaseOS/Packages/* /localrepo

unpack iso BaseOS to localrepo
-r recursive

-v verbose

cp -rv /mnt/rhel-dvd/AppStream/* /localrepo

unpack iso AppStream to localrepo

dnf install createrepo_c -y

installs the createrepo_c utility

createrepo /localrepo/

scan folder and build the necessary XML metadata in the repository

so dnf/yum can index package names, versions & dependencies

cd /etc/yum.repos.d

go to the location that dns reads .repo (config) files from

mkdir backup

backup existing repo files for later

mv *.repo backup

move any existing repos to backup, disables default Red Hat online repositories

ensures the system only uses local repositories

nano local.repo

[localrepo]

name=localrepo

baseurl=file:///localrepo/

enabled=1

gpgcheck=0

metadata_expire=-1

create a local .repo (config) file for local repositories

repository header

human readable name to show up in lists

exact path to the files, file:/// tells the system to look at a local directory /localrepo/ rather than http://

enabled the repository

disable verification check for security signatures (GPG keys) on the packages

Disable metadata expiry

dnf clean all

delete cached repository metadata and package indexes (existing .repo's)

dnf repolist

list all active software sources

dnf install httpd -y

verifies the local repository can support package installations

dnf install podman -y

install podman

alias docker=podman

used when switching from docker to podman

podman -v

check podman version

podman info

check podman environment (see registries)
if loading an image, looks locally, then to registries by order listed

podman search httpd

search container registries for an image

podman pull docker.io/library/httpd

download image from a registry

podman images

list downloaded images

podman run -d --name web1 -p 8080:80 docker.io/library/httpd

create & start a container from an image

podman ps

list running containers

curl localhost:8080 (or web) http://localhost:8080

verify application is accessible

podman stop web1

stop a container gracefully

podman rm -f web1

remove a container

podman pull docker.io/library/httpd

download image from a registry

podman create --name web2 -p 8081:80 docker.io/library/httpd

create a container

podman ps -a

verify status is created
-a all containers

podman start web2

start an existing container

podman ps

verify container status is running

curl localhost:8081 (or web) http://localhost:8081

verify application is accessible

podman logs web2

view output generated by container

mkdir -p /etc/containers/systemd

create directory for quadlet definitions

nano /etc/containers/systemd/web3.container
…

[Unit]

Description=Apache Web Container

[Container]

Image=docker.io/library/httpd

ContainerName=web3

PublishPort=8082:80

[Service]

Restart=always

[Install]

WantedBy=multi-user.target

create quadlet container definition file

define systemd metadata
description

define container-specific settings
specifies container image
assigns name
maps host port to container port

defines systemd behaviour
automatically restart container if it stops

definte boot settings
allow service to start automatically during boot

systemctl daemon-reload

reload systemd configuration

systemctl enable --now web3.service

enable service at boot and start now

systemctl status web3.service

verify service status

podman ps

verify container status is running

curl localhost:8082 (or web) http://localhost:8082

verify application is accessible

fdisk -l

disk partition utility (displays disk system names)
-l list disks

lsblk -f

list block devices (displays UUID)
-f forest (tree) hierarchy

df -h

filesystem capacity (displays mounted disks)

-h human readable

insert a new 2GB disk

fdisk /dev/sdb

enter fdisk utility for the new disk

n

new partition

enter (default)

new standalone disk

enter (default)

first sector 2048 last sector 67108863
(whole disk = 1 partition)

enter (default)

w

write (apply)

mkfs.xfs /dev/sdb1

create xfs filesystem for the disk

mkdir /data

create directory to mount the disk to

lsblk -f

retrieve UUID

mount /dev/sdb1 /data

mount the disk to the directory

nano /etc/fstab

add the below line to mount during boot (spaces = tab)
/dev/sdb1    /data    xfs    defaults    0 0

UUID=4461ddd4-6c2c-4078-ab90-d4514368dd09    /data    xfs    defaults    0 0

reboot

verify successful boot

umount /data

to unmount

mount -a

mount disks again according to /etc/fstab

Physical Volume

Volume Group

Logical Volume

Mounted On

Disk 1

rootvg

system

/

home

/home

swap

Disk 2

datavg

data1

/data1

Disk 3

data2

/data2

Disk 4

data3

/data3

data4

/data4

File system

datafs

Logical Volume(s)

datalv

Volume Group

datavg

Physical Volume

/dev/sda1

/dev/sdb1

/dev/sdc1

Partitions

/dev/sda1

/dev/sdb1

/dev/sdc1

Hard Disks

/dev/sda

/dev/sdb

/dev/sdc

pvdisplay

display phsyical volumes

pvs

summary physical volumes

vgdisplay

display volume groups

vgs

summary volume groups

lvdisplay

display logical volumes

lvs

summary logical volumes

insert a new 1GB disk

fdisk /dev/sdc

enter fdisk utility for the new disk

n

new partition

enter (default)

new standalone disk

enter (default)

first sector 2048 last sector 67108863
(whole disk = 1 partition)

enter (default)

p

show partitions

t

change partition type

L

show LVM hex codes

8e

Linux LVM

w

write (apply)

pvcreate /dev/sdc1

create physical volume

vgcreate vg_app /dev/sdc1

create volume group

lvcreate -n lv_app --size 1020M vg_app

create logical volume (allowing overhead)

mkfs.xfs /dev/vg_app/lv_app

create filesystem

blkid /dec/vg_app/lv_app

retrieve UUID

mkdir app

create directory

mount /dev/vg_app/lv_app /app

mount

nano /etc/fstab

UUID=12345678-abcd-1234-efgh-123456789abc  /app  xfs  defaults  0 0

insert a new 1GB disk

fdisk /dev/sdd

enter fdisk utility for the new disk

n

new partition

enter (default)

new standalone disk

enter (default)

first sector 2048 last sector 67108863
(whole disk = 1 partition)

enter (default)

p

show partitions

t

change partition type

8e

Linux LVM

w

write (apply)

pvcreate /dev/sdd1

create phsyical volume

vgextend vg_app /dev/sdd1

extend vg_app to new disk

lvextend -L+1020M /dev/mapper/vg_app-lv_app

extend by 1020MB lv_app

xfs_growfs /dev/mapper/vg_app-lv_app

extend filesystem for lv_app

dnf install stratis-cli stratisd

Install stratis and daemon

systemctl enable/start stratisd

Enable and start the daemon

lsblk -f

stratis pool list

stratis filesystem list

insert two new 5GB disks

stratis pool create pool1 /dev/sde

create stratis pool

stratis pool add-data pool1 /dev/sdf

extend stratis pool to another disk

stratis filesystem create pool1 fs1

create stratis filesystem

mkdir /bigdata

mount /dev/stratis/pool1/fs1 /bigdata

stratis filesystem snapshot pool1 fs1 fs1-snap

create a snapshot

nano /etc/fstab

…

UUID=a6dca899-feab-4663-8028-fe6ce748d268 /bigdata xfs defaults,x-systemd.requires=stratisd.service 0 0

tells fstab to not mount this filesystem unless the system starts stratisd daemon

(UUID of the filesystem)
 

dnf install nfs-utils -y

install nfs utilities

systemctl enable --now nfs-server

start and enable nfs service

mkdir -p /srv/nfsshare

create NFS share directory

chmod -R 0777 /srv/nfsshare

open permissions (0777 for lab)

semanage fcontext -a -t public_content_rw_t "/srv/nfsshare(/.*)?"

assign selinux context

restorecon -Rv /srv/nfsshare

apply selinux context

ls -Zd /srv/nfsshare

verify selinux context

nano /etc/exports

…

/srv/nfsshare 192.168.17.0/24(rw,sync,no_root_squash)

export share to subnet with read-write access

exportfs -arv

reload and verify exports

firewall-cmd --add-service=nfs --permanent

allow nfs through firewall

firewall-cmd --add-serivce=rpc-bind --permanent

NFSv4 alone works over port 2049, but showmount

and legacy tools need rpc-bind and mountd ports

firewall-cmd --add-service=mountd --permanent

firewall-cmd --reload

reload firewall rules

exportfs -v | grep /srv/nfsshare

verify export configuration

ip a

confirm subnet

showmount -e 192.168.17.185

verify server is exporting

sudo dnf install nfs-utils -y

install nfs utilities

sudo mkdir -p /mnt/nfsshare

create nfs mount directory

sudo mount -t nfs -o vers=4.2 192.168.17.185:/srv/nfsshare /mnt/nfsshare

mount nfs share

df -h | grep nfsshare

verify

echo "Created from client" | sudo tee /mnt/nfsshare/client.txt >/dev/null

test write access

sudo nano /etc/fstab

…

192.168.17.185:/srv/nfsshare  /mnt/nfsshare  nfs  _netdev,vers=4.2,rw  0  0

persistent nfs mount entry

sudo systemctl daemon-reload

reload systemd config

sudo mount -a

test fstab config

reboot

verify mount survives

dnf install -y samba policycoreutils-python-utils

install samba server and selinux tools

mkdir -p /srv/sambashare

create samba share directory

echo "This is a samba file" > /srv/sambashare/readme.txt

create test file

chmod -R 0777 /srv/sambashare

open permissions (0777 for lab)

nano /etc/samba/smb.conf

…

[sambashare]

path = /srv/sambashare

browsable = yes

writable = yes

guest ok = yes

read only = no

define samba share configuration

testparm -s

validate samba config

semanage fcontext -a -t samba_share_t "/srv/sambashare(/.*)?"

assign selinux context

restorecon -Rv /srv/sambashare

apply selinux context

ls -Zd /srv/sambashare

verify selinux context

firewall-cmd --add-service=samba --permanent

allow samba through firewall

firewall-cmd --reload

reload firewall rules

systemctl enable --now smb

start and enable samba service

systemctl status smb --no-pager

verify status

sudo dnf install -y samba-client cifs-utils

install samba client tools

smbclient -L //192.168.17.185 -N

list available samba shares

smbclient //192.168.17.185/sambashare -N

connect to samba share

ls

list files in share

get readme.txt

download file from share

quit

exit smbclient session

sudo mkdir -p /mnt/sambashare

create mount directory

sudo mount -t cifs //192.168.17.185/sambashare /mnt/sambashare -o guest

mount samba share

ls -l /mnt/sambashare

verify share contents

echo "Client wrote this via Samba" | sudo tee /mnt/sambashare/client.txt >/dev/null

create file on share

sudo nano /etc/fstab
…
//192.168.17.185/sambashare  /mnt/sambashare  cifs  _netdev,guest  0  0

configure persistent mount

sudo mount -a

test fstab config

reboot

verify mount survives

systemctl poweroff

stops all services, unmounts file systems, powers off system

poweroff

systemctl reboot

all of the above plus reboot

reboot

systemctl get-default

check current target

who -r

run level

systemctl list-dependencies graphical.target | grep target

list target dependencies

ls -l /lib/systemd/system/runlevel*

list run levels

systemctl set-default graphical.target

set default target

Reboot

Press esc to get to grub

Find line beginning with Linux, add " rd.break" to the end

RHEL 9 boot into emergency recovery mode

Find line beginning with Linux, add "init=/bin/bash" to the end

RHEL 10 boot into emergency recovery mode

Press Ctrl X

start boot using the modified settings

mount -o remount,rw /sysroot

RHEL 9 remount the root filesystem as read-write to allow changes

mount -o remount,rw /

RHEL 10 remount the root filesystem as read-write to allow changes

chroot /sysroot

change root to /sysroot (RHEL OS)

passwd

Enter your new password

touch /.autorelabel

Force SELinux to relabel files on next boot

exit

RHEL 9 exit back to emergency shell

mount -o remount,ro /

RHEL 10 reboot cleanly

exit

exit to boot

Corrupt file system

systemd attempts to repair file system
if it cannot be repaired, go to emergency shell

nonexistent device/UUID in /etc/fstab

if device remains unavailable, go to emergency shell

nonexistent mount point in /etc/fstab

go to emergency shell

incorrect mount option in /etc/fstab

go to emergency shell

systemctl daemon-reload

when using emergency shell, remember to run this after editing /etc/fstab