RedHat

RHEL | User, Group and Password
RHEL | Mounting ISO and Setting as Local Repo
realmd/sssd | Joining a Domain with RHEL and logging in with AD account
chrony | Set up NTP Server and Client
timedatectl | Change Date/Time in RHEL
tar | File Archive Commands
scp | Push/Pull Files/Directory
rsync | Synchronise between systems
LVM | Create/Extend
RHEL | Mounting ISO and Setting as Local Repo

RHEL | User, Group and Password

User Management

Add new user

useradd

Create a user and set the primary group to something else

sudo useradd -G consultants consultant3

Delete User

userdel johndoe1

Append group to user

usermod -aG sudo myusername

Group Management

Add new group

groupadd

Delete Group

groupdel groupname

Create a new group called consultants with a GID of 35000. (-g is id)

groupadd -g 35000 consultants

Password Management

Change the default max password age

sudo vim /etc/login.defs

Require a new password every 15 days (-M is max days)

chage -M 15 username

Require user to change password on first login (-d )

chage -d 0 username

Change to password date expiry

chage -E 2023-01-27 username

Edit password configs

/etc/login.defs

RHEL | Mounting ISO and Setting as Local Repo

Prerequisite

A Free RedHat Account
Official Redhat Linux ISO

No Redhat license is required.

Step 1: Identify the Red Hat OS version

Run the following command in the terminal:

cat /etc/os-release

Look for the line VERSION="8.7 (Ootpa)" in the output. This will show the version number.

[user@lab-rhel8 ~]$ cat /etc/os-release
NAME="Red Hat Enterprise Linux"
VERSION="8.7 (Ootpa)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="8.7"
PLATFORM_ID="platform:el8"
PRETTY_NAME="Red Hat Enterprise Linux 8.7 (Ootpa)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:8::baseos"
HOME_URL="https://www.redhat.com/"
DOCUMENTATION_URL="https://access.redhat.com/documentation/red_hat_enterprise_linux/8/"
BUG_REPORT_URL="https://bugzilla.redhat.com/"

Step 2: Download the RHEL ISO of the correct version

If you do not have an account, you must register a free account before downloading. Download the RHEL ISO of your version from the official RHEL download website.

Step 3: Mount the ISO from your Hypervisor

From your Hyper-V manager, add the ISO to the DVD drive device of the Virtual Machine.

Step 4: Identify the DVD Drive inside Red Hat Linux

Run the following to identify the correct device name of the DVD drive: lsblk

Look for the label rom in the TYPE column. For below example, it is sr0. This means that DVD drive is located at /dev/sr0. Take note of this device.

[user@lab-rhel8 ~]$ lsblk
NAME                   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                      8:0    0  100G  0 disk
├─sda1                   8:1    0    2G  0 part /boot
└─sda2                   8:2    0   97G  0 part
  ├─rhel-tmp           253:0    0    5G  0 lvm  /tmp
  ├─rhel-var_log       253:1    0   20G  0 lvm  /var/log
  ├─rhel-var           253:2    0   10G  0 lvm  /var
  ├─rhel-swap          253:3    0   12G  0 lvm  [SWAP]
  ├─rhel-home          253:4    0   10G  0 lvm  /home
  ├─rhel-root          253:5    0   30G  0 lvm  /
  ├─rhel-var_log_audit 253:6    0    5G  0 lvm  /var/log/audit
  └─rhel-var_tmp       253:7    0    5G  0 lvm  /var/tmp
sdb                      8:16   0  300G  0 disk
└─sdb1                   8:17   0  300G  0 part /appdata
sr0                     11:0    1  6.6G  0 rom

Step 5: Create a Mountpoint and mount the DVD Drive locally

For this guide, the mountpoint used will be in /mnt/disc.

Run the following command file /mnt/disc to create a mountpoint, if it does not exist yet.

Output will show No such file or directory if it does not exist.

[user@lab-rhel8 ~]$ file /mnt/disc
/mnt/disc: cannot open `/mnt/disc' (No such file or directory)

Create the mountpoint /mnt/disc directory with sudo mkdir /mnt/disc.

[user@lab-rhel8 ~]$ sudo mkdir /mnt/disc
[user@lab-rhel8 ~]$ file /mnt/disc
/mnt/disc: directory

Next, mount the DVD drive (/dev/sr0) to the mountpoint (/mnt/disc) with the command mount -o loop RHEL7.9.iso /mnt/disc.

[user@lab-rhel8 ~]$ sudo mount -o loop /dev/sr0 /mnt/disc

With the DVD drive mounted, you can now list the content inside the disc with ls -al /mnt/disc.

[user@lab-rhel8 ~]$ ls -al /mnt/disc
total 53
dr-xr-xr-x. 7 root root  2048 Apr  4  2019 .
drwxr-xr-x. 3 root root    18 May 12 14:51 ..
dr-xr-xr-x. 4 root root  2048 Apr  4  2019 AppStream
dr-xr-xr-x. 4 root root  2048 Apr  4  2019 BaseOS
-r--r--r--. 1 root root    60 Apr  4  2019 .discinfo
dr-xr-xr-x. 3 root root  2048 Apr  4  2019 EFI
-r--r--r--. 1 root root  8266 Mar  1  2019 EULA
-r--r--r--. 1 root root  1455 Apr  4  2019 extra_files.json
-r--r--r--. 1 root root 18092 Mar  1  2019 GPL
dr-xr-xr-x. 3 root root  2048 Apr  4  2019 images
dr-xr-xr-x. 2 root root  2048 Apr  4  2019 isolinux
-r--r--r--. 1 root root   103 Apr  4  2019 media.repo
-r--r--r--. 1 root root  1669 Mar  1  2019 RPM-GPG-KEY-redhat-beta
-r--r--r--. 1 root root  5134 Mar  1  2019 RPM-GPG-KEY-redhat-release
-r--r--r--. 1 root root  1796 Apr  4  2019 TRANS.TBL
-r--r--r--. 1 root root  1566 Apr  4  2019 .treeinfo

Step 6: Copying the media.repo file

Copy the media.repo file from the root of the mounted directory to /etc/yum.repos.d/ and set the permissions to 644.

[user@lab-rhel8 ~]$ sudo cp /mnt/disc/media.repo /etc/yum.repos.d/rhel8dvd.repo
[user@lab-rhel8 ~]$ sudo chmod 644 /etc/yum.repos.d/rhel8dvd.repo

Step 7: Editing the rhel8dvd.repo

Edit the new repo file:

[user@lab-rhel8 ~]$ sudo vi /etc/yum.repos.d/rhel8dvd.repo

Copy the following into the file:

[InstallMedia-BaseOS]
name=Red Hat Enterprise Linux DVD BaseOS
mediaid=None
metadata_expire=-1
gpgcheck=1
cost=500
enabled=1
baseurl=file:///mnt/disc/BaseOS
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

[InstallMedia-AppStream]
name=Red Hat Enterprise Linux DVD AppStream
mediaid=None
metadata_expire=-1
gpgcheck=1
cost=500
enabled=1
baseurl=file:///mnt/disc/AppStream
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

Disable the any repo files that is not in use. Look for the line enabled = 1 and make sure that all are set to enabled = 0 in the other repo files.

[user@lab-rhel8 ~]$ cd /etc/yum.repos.d/
[user@lab-rhel8 yum.repos.d]$ sudo vi redhat.repo

Step 8: Clear the yum cache

Clear the cache and check whether you can get the packages list from the DVD repo

[user@lab-rhel8 ~]$ sudo yum clean all
[user@lab-rhel8 ~]$ sudo yum repolist enabled
Updating Subscription Management repositories.
repo id                                         repo name
InstallMedia-BaseOS                             Red Hat Enterprise Linux 8.7.0 BaseOS
InstallMedia-AppStream                          Red Hat Enterprise Linux 8.7.0 AppStream

Now, you can install any packages with yum install <packagename> or update installed packages with yum update.

Disabling the Local Repo and Unmounting the DVD

This step is to be done before unmounting the DVD. To disable the local repo, simply delete the local repo file.

[user@lab-rhel8 ~]$ cd /etc/yum.repos.d
[user@lab-rhel8 yum.repos.d]$ sudo rm rhel8dvd.repo

Unmount the DVD Drive from the mountpoint

[user@lab-rhel8 yum.repos.d]$ sudo umount /mnt/disc

realmd/sssd | Joining a Domain with RHEL and logging in with AD account

Install the necessary packages and join a domain

SSSD = Authentication service from a remote source such as AD
realmd = Active Directory service

Install the packages

yum install sssd realmd oddjob oddjob-mkhomedir adcli samba-common samba-common-tools krb5-workstation openldap-clients python3-policycoreutils

Check if can discover the domain

realm discover homelab.local

Join Domain

# realm join --user=[domain user account] [domain name]
realm join --user=aki.adm homelab.local

Check if it is inside a domain after joining

realm list

Further configuration

So now that the Linux server is part of the AD domain, domain users can access the server with their usual credentials. We are done, right? Wrong. "What's the problem?" I hear you say. HAHAHHAH

Configure SSSD

Its main configuration file is located at /etc/sssd/sssd.conf. As a matter of fact, this is the main configuration file we will modify.

Configure the SSSD conf to look like this. From line 17!

[sssd]
domains = homelab.local
config_file_version = 2
services = nss, pam

[domain/homelab.local]
ad_domain = homelab.local
krb5_realm = HOMELAB.LOCAL
realmd_tags = manages-system joined-with-adcli
cache_credentials = True
id_provider = ad
krb5_store_password_if_offline = True
default_shell = /bin/bash
ldap_id_mapping = True
use_fully_qualified_names = True
fallback_homedir = /home/%u@%d
access_provider = simple
ad_hostname = lab-dc1.homelab.local
dyndns_update = true
dyndns_refresh_interval = 43200
dyndns_update_ptr = true
dyndns_ttl = 3600
dyndns_auth = GSS-TSIG

Once the configuration is complete, restart sssd to apply settings immediately.

systemctl restart sssd

Shows the permitted or denied login
By default, this is the output without configurations

[root@lab-rhel8 ~]# realm list
homelab.local
  type: kerberos
  realm-name: HOMELAB.LOCAL
  domain-name: homelab.local
  configured: kerberos-member
  server-software: active-directory
  client-software: sssd
  required-package: oddjob
  required-package: oddjob-mkhomedir
  required-package: sssd
  required-package: adcli
  required-package: samba-common-tools
  login-formats: %U@homelab.local
  login-policy: allow-permitted-logins
  permitted-logins:
  permitted-groups:

Deny all

realm deny --all

The following options can be used:
--all, -a
This option should be specified
--realm, -R
Specify the name of the realm to deny users login to.

Permit All (Default)

Permit logins using realm accounts on the local machine according to the realm policy. This usually defaults to allowing any realm user to log in.

realm permit --all
realm permit -a

Permit User

realm permit user@example.com
realm permit DOMAIN\\User2

Permit Group

realm permit --groups "Domain Admin"
realm permit -g "Domain Admin"

Permit Realm (if joining more than one domain)

realm permit --realm 
realm permit -R homelab.local

Remove Permit

realm permit --withdraw user@example.com
realm permit -x user@example.com

chrony | Set up NTP Server and Client

NTP Server

Step 1: Install Chrony NTP package

yum install chrony

Step 2: Enable Chrony to start after boot:

systemctl enable chronyd

Step 3: Set Chrony to act as an NTP server for a local network

To turn Chrony into an NTP server, add the following line to the main Chrony /etc/chrony.conf configuration file. Change the address to your network address.

allow 10.1.1.0/24

Step 4: Restart Chrony NTP daemon to apply the changes

systemctl restart chronyd

Step 5: Open the firewall port to allow for incoming NTP requests

firewall-cmd --permanent --add-service=ntp
firewall-cmd --reload

NTP Client

Step 1: Install Chrony NTP package

yum install chrony

Step 2: Enable Chrony to start after boot:

systemctl enable chronyd

Step 3: Set Chrony to act as an NTP client

Add the following line in the Chrony /etc/chrony.conf configuration file: Change the IP address to your NTP server.

Server 10.1.1.10

Step 4: Restart Chrony NTP daemon to apply the changes

systemctl restart chronyd

Step 5: Check for NTP server sources.

Your local NTP server should be listed:

chronyc sources
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^? LAB-DC1.lab.local         4   6     1     2    +31us[  +31us] +/-   44ms

timedatectl | Change Date/Time in RHEL

Show Status

To display status

timedatectl

Disable/Enable NTP

Firstly, temporarily disable the NTP service, if active.

timedatectl set-ntp no

To enable.

timedatectl set-ntp yes

Change Time

We must adhere to the following syntax rule to change the current local time where HH is for hours, MM for minutes, and SS for seconds.

timedatectl set-time HH:MM:SS
timedatectl set-time 18:05:00

Change Date

To change the current date, adhere to the following command syntax where YYYY is for a year, MM for a month, and DD for a day.

timedatectl set-time YYYY-MM-DD
timedatectl set-time 2021-11-17

Change Timezone

List timezone

timedatectl list-timezones

To change/edit the Time Zone you are under, adhere to the following command syntax.

timedatectl set-timezone your_preferred_time_zone
timedatectl set-timezone Asia/Singapore

tar | File Archive Commands

TAR (No Compression)

Create TAR Archive

Create a TARarchive from a directory. "-cf" is to create and append. No compression.

tar -cf <filename> <dir>

Extract TAR Archive

Extract the TAR file to the current directory.

tar -xf <filename>

View TAR Archive

View the content of the TAR file.

tar -tf <filename>

TAR (With Compression)

Create a TAR file with compression

Create a TAR archive with compression. The order of the letter is important.

(gzip) $ tar -czf <filename> <dir> 
(bzip2) $ tar -cjf <filename> <dir>
(xz) $ tar -cJf <filename> <dir>

Extract a compressed TAR file

Extract a compressed TAR file to the current directory.

(gzip) $ tar -xzf <filename>
(bzip2) $ tar -xjf <filename>
(xz) $ tar -xJf <filename>

Preserve Permission and Verbose

Create a compressed TAR file and preserve permissions.

(gzip) $ tar -cvpzf <filename> <dir> 
(bzip2) $ tar -cvpzf <filename> <dir>
(xz) $ tar -cvpzf <filename> <dir>

permission gzip

scp | Push/Pull Files/Directory

To copy files/folders from one system to another system

scp <source> <dest>

Pull file.txt to home directory

scp username@host:/file.txt ~/

Push file.txt to other system home directory

scp ~/file.txt username@host:~/file.txt

rsync | Synchronise between systems

Sync

rsync command

rsync <source> <dest>

Local

Between the same system between directory

rsync -av /var/log /tmp

Remote

Between the local directory and the remote directory

rsync -av /tmp username@remote_host:/tmp

Compare

Compare the content of the source and remote directory

rsync -anv <source> <dest>

LVM | Create/Extend

Create LVM

Steps

In sequence,

Prepare the physical storage
Create the physical volume
Create the volume group from the physical volume
Create logical volume from the volume group
Make an XFS File System from the logical volume
Mount the XFS FS

Step 1: Prepare the physical storage

Create a partition if don’t want to use the whole volume

parted
udevadm settle

Step 2: Create the physical volume

Create a physical volume out of a partition or whole disk. In this example, there are two partitions vdb1 and vdb2.

# pvreate <device/partition>
pvcreate /dev/vdb1
pvcreate /dev/vdb2

Display the physical group

To display the volume group.

pvdisplay

# pvdisplay <device/partition>
pvdisplay /dev/vda1

Step 3: Create the volume group from the physical volume

Create the volume group with the physical device

# vgcreate <name> <member of physical volume>
vgcreate vg01 /dev/vdb1 /dev/vdb2

Display the volume group

To display the volume group.

vgdisplay

# vgdisplay <vgname>
vgdisplay vg01

Step 4: Create logical volume from the volume group

Create logical volume from a volume group

# lvcreate -n <name> -L <size> <source vg>

# 400M size 
lvcreate -n lv01 -L 400M vg01

# 100% size
lvcreate -n lv01 -L +100%FREE vg01

Display the logical volume

Display the stats of logical volume

lvdisplay

Step 5: Make an XFS File System from the logical volume

Make an XFS file system

# mkfs.xfs <path to lv>
mkfs.xfs /dev/vg01/lv01

Step 6: Mount the XFS FS

mkdir /data
mount /dev/vg01/lv01 /data

Extend Logical Volume

Steps

In sequence,

Extend the volume group
Extend the logical volume
Extend the File System
Display the stats of logical volume

Step 1: Extend the volume group

Prepare the physical storage or partition it if required. In this example, vdb3 is used to be included inside existing volume group vg01..

parted /dev/vdb3

Extend with vgextend.

vgextend vg01 /dev/vdb3

Step 2: Extend the logical volume

Extend logical volume in a logical group

# lvextend
lvextend -l +100%FREE /dev/vg01/lv01

Step 3: Extend the File System

XFS

# xfs_growfs <path to lv>
xfs_growfs /dev/vg01/lv01

Other FS

# resize2fs <path to lv>
resize2fs /dev/vg01/lv01

Step 4: Display the stats of logical volume

lvdisplay

RHEL | Mounting ISO and Setting as Local Repo

This document provides a guide on mounting the RHEL ISO and setting it up as a local repo. This will enable RedHat Linux to install and update RPM packages.

This guide may work on another type of Linux as it is based on editing the repo file and mounting ISO media.

Prerequisite

A Free RedHat Account
Official Redhat Linux ISO

No Redhat license is required.

Step 1: Identify the Red Hat OS version

Run the following:

cat /etc/os-release

Look for the line VERSION="8.7 (Ootpa)" in the output. This will shows the version number.

[user@demo ~]$ cat /etc/os-release
NAME="Red Hat Enterprise Linux"
VERSION="8.7 (Ootpa)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="8.7"
PLATFORM_ID="platform:el8"
PRETTY_NAME="Red Hat Enterprise Linux 8.7 (Ootpa)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:8::baseos"
HOME_URL="https://www.redhat.com/"
DOCUMENTATION_URL="https://access.redhat.com/documentation/red_hat_enterprise_linux/8/"
BUG_REPORT_URL="https://bugzilla.redhat.com/"

Step 2: Download the RHEL ISO of the correct version

If you do not have an account, you must register a free account before downloading. Download the RHEL ISO of your version from the official RHEL download website.

Step 3: Mount the ISO from your Hypervisor

From your Hyper-V manager, add the ISO to the DVD drive device of the Virtual Machine.

Step 4: Identify the DVD Drive inside Red Hat Linux

Run the following to identify the correct device name of the DVD drive: lsblk

Look for the label rom in the TYPE column. For below example, it is sr0. This means that the DVD drive is located at /dev/sr0. Take note of this device.

[user@demo ~]$ lsblk
NAME                   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                      8:0    0  100G  0 disk
├─sda1                   8:1    0    2G  0 part /boot
└─sda2                   8:2    0   97G  0 part
  ├─rhel-tmp           253:0    0    5G  0 lvm  /tmp
  ├─rhel-var_log       253:1    0   20G  0 lvm  /var/log
  ├─rhel-var           253:2    0   10G  0 lvm  /var
  ├─rhel-swap          253:3    0   12G  0 lvm  [SWAP]
  ├─rhel-home          253:4    0   10G  0 lvm  /home
  ├─rhel-root          253:5    0   30G  0 lvm  /
  ├─rhel-var_log_audit 253:6    0    5G  0 lvm  /var/log/audit
  └─rhel-var_tmp       253:7    0    5G  0 lvm  /var/tmp
sdb                      8:16   0  300G  0 disk
└─sdb1                   8:17   0  300G  0 part /data
sr0                     11:0    1  6.6G  0 rom

Step 5: Create a mountpoint and mount the DVD Drive locally

For this guide, the mountpoint used will be in /mnt/disc.

Run the following command. file /mnt/disc to create a mount point if it does not exist yet.

Output will show No such file or directory if it does not exist.

[user@demo ~]$ file /mnt/disc
/mnt/disc: cannot open `/mnt/disc' (No such file or directory)

Create the mountpoint /mnt/disc directory with sudo mkdir /mnt/disc.

[user@demo ~]$ sudo mkdir /mnt/disc
[user@demo ~]$ file /mnt/disc
/mnt/disc: directory

Next, mount the DVD drive (/dev/sr0) to the mountpoint (/mnt/disc) with the command mount -o loop RHEL7.9.iso /mnt/disc.

[user@demo ~]$ sudo mount -o loop /dev/sr0 /mnt/disc

With the DVD drive mounted, you can now list the content inside the disc with ls -al /mnt/disc.

[user@demo ~]$ ls -al /mnt/disc
total 53
dr-xr-xr-x. 7 root root  2048 Apr  4  2019 .
drwxr-xr-x. 3 root root    18 May 12 14:51 ..
dr-xr-xr-x. 4 root root  2048 Apr  4  2019 AppStream
dr-xr-xr-x. 4 root root  2048 Apr  4  2019 BaseOS
-r--r--r--. 1 root root    60 Apr  4  2019 .discinfo
dr-xr-xr-x. 3 root root  2048 Apr  4  2019 EFI
-r--r--r--. 1 root root  8266 Mar  1  2019 EULA
-r--r--r--. 1 root root  1455 Apr  4  2019 extra_files.json
-r--r--r--. 1 root root 18092 Mar  1  2019 GPL
dr-xr-xr-x. 3 root root  2048 Apr  4  2019 images
dr-xr-xr-x. 2 root root  2048 Apr  4  2019 isolinux
-r--r--r--. 1 root root   103 Apr  4  2019 media.repo
-r--r--r--. 1 root root  1669 Mar  1  2019 RPM-GPG-KEY-redhat-beta
-r--r--r--. 1 root root  5134 Mar  1  2019 RPM-GPG-KEY-redhat-release
-r--r--r--. 1 root root  1796 Apr  4  2019 TRANS.TBL
-r--r--r--. 1 root root  1566 Apr  4  2019 .treeinfo

Step 6: Copying the media.repo file

Copy the media.repo file from the root of the mounted directory to /etc/yum.repos.d/ and set the permissions to 644.

[user@demo ~]$ sudo cp /mnt/disc/media.repo /etc/yum.repos.d/rhel8dvd.repo
[user@demo ~]$ sudo chmod 644 /etc/yum.repos.d/rhel8dvd.repo

Step 7: Editing the rhel8dvd.repo

Edit the new repo file:

[user@demo ~]$ sudo vi /etc/yum.repos.d/rhel8dvd.repo

Copy the following into the file:

[InstallMedia-BaseOS]
name=Red Hat Enterprise Linux DVD BaseOS
mediaid=None
metadata_expire=-1
gpgcheck=1
cost=500
enabled=1
baseurl=file:///mnt/disc/BaseOS
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

[InstallMedia-AppStream]
name=Red Hat Enterprise Linux DVD AppStream
mediaid=None
metadata_expire=-1
gpgcheck=1
cost=500
enabled=1
baseurl=file:///mnt/disc/AppStream
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

Disable any repo files that are not in use. Look for the line enabled = 1 and make sure that all are set to enabled = 0 in the other repo files.

[user@demo ~]$ cd /etc/yum.repos.d/
[user@demo yum.repos.d]$ sudo vi redhat.repo

Step 8: Clear the yum cache

Clear the cache and check whether you can get the packages list from the DVD repo

[user@demo ~]$ sudo yum clean all
[user@demo ~]$ sudo yum repolist enabled
Updating Subscription Management repositories.
repo id                                         repo name
InstallMedia-BaseOS                             Red Hat Enterprise Linux 8.7.0 BaseOS
InstallMedia-AppStream                          Red Hat Enterprise Linux 8.7.0 AppStream

Now, you can install any package with yum install <packagename> or update installed packages with yum update.

Disabling the Local Repo and Unmounting the DVD

This step should be completed before unmounting the DVD. To disable the local repo, delete the local repo file.

[user@demo ~]$ sudo rm rhel8dvd.repo

Unmount the DVD Drive from the mountpoint

[user@demo ~]$ sudo umount /mnt/disc

Now, you can remove the ISO from the DVD drive from the hypervisor.

RedHat

RHEL | User, Group and Password

User Management

Add new user

Create a user and set the primary group to something else

Delete User

Append group to user

Group Management

Add new group

Delete Group

Create a new group called consultants with a GID of 35000. (-g is id)

Password Management

Change the default max password age

Require a new password every 15 days (-M is max days)

Require user to change password on first login (-d )

Change to password date expiry

Edit password configs

RHEL | Mounting ISO and Setting as Local Repo

Prerequisite

Step 1: Identify the Red Hat OS version

Step 2: Download the RHEL ISO of the correct version

Step 3: Mount the ISO from your Hypervisor

Step 4: Identify the DVD Drive inside Red Hat Linux

Step 5: Create a Mountpoint and mount the DVD Drive locally

Step 6: Copying the media.repo file

Step 7: Editing the rhel8dvd.repo

Step 8: Clear the yum cache

Disabling the Local Repo and Unmounting the DVD

Links

realmd/sssd | Joining a Domain with RHEL and logging in with AD account

Install the necessary packages and join a domain

Install the packages

Check if can discover the domain

Join Domain

Check if it is inside a domain after joining

Further configuration

Configure SSSD

Managing Login Permissions for Domain Users

Deny all

Permit All (Default)

Permit User

Permit Group

Permit Realm (if joining more than one domain)

Remove Permit

chrony | Set up NTP Server and Client

NTP Server

Step 1: Install Chrony NTP package

Step 2: Enable Chrony to start after boot:

Step 3: Set Chrony to act as an NTP server for a local network

Step 4: Restart Chrony NTP daemon to apply the changes

Step 5: Open the firewall port to allow for incoming NTP requests

NTP Client

Step 1: Install Chrony NTP package

Step 2: Enable Chrony to start after boot:

Step 3: Set Chrony to act as an NTP client

Step 4: Restart Chrony NTP daemon to apply the changes

Step 5: Check for NTP server sources.

timedatectl | Change Date/Time in RHEL

Show Status

Disable/Enable NTP

Change Time

Change Date

Change Timezone

tar | File Archive Commands

TAR (No Compression)

Create TAR Archive

Extract TAR Archive

View TAR Archive

TAR (With Compression)

Create a TAR file with compression

Extract a compressed TAR file

Preserve Permission and Verbose

scp | Push/Pull Files/Directory

rsync | Synchronise between systems

Sync

Local

Remote

Compare

LVM | Create/Extend

Create LVM