DEV Community: Josh

File System and Disk Management Linux

Josh — Fri, 13 Dec 2024 19:19:34 +0000

Disk Space and Usage Commands

Display Disk Space Information

Command: df

Description: Displays the amount of disk space used and available on filesystems.
Command: df -h

Description: Provides a human-readable format (e.g., in GB or MB) for easier interpretation of disk space usage.

Display Disk Usage

Command: du ~

Description: Shows the disk usage of your home directory, listing the size of each subdirectory.
Command: du -sh ~

Description: Gives a summary of the total disk usage in your home directory, displaying it in a human-readable format.

Creating a Virtual Disk

To create a virtual disk, use the following command:


bash
dd if=/dev/zero of=vdisk.img bs=1M count=256
Explanation of Parameters
if=/dev/zero: Specifies the input file as /dev/zero, a special file that produces null bytes. This is useful for creating empty files or disks.
of=vdisk.img: Sets the output file to vdisk.img, which will be the virtual disk created.
bs=1M: Defines both the input and output block size as 1 megabyte, optimizing the speed of the operation.
count=256: Limits the operation to 256 blocks, resulting in a total size of 256 MB for the virtual disk.
Verifying the Virtual Disk
To verify the creation of the virtual disk, run:
bash


ls -lh vdisk.img
This command lists the details of vdisk.img, including its size and permissions.
Formatting the Virtual Disk
Format the virtual disk with the ext4 filesystem using the following command:
bash


sudo mkfs.ext4 vdisk.img
Additional Details
The mkfs.ext4 command creates an ext4 filesystem on the specified file. This is commonly used for new disks or partitions, ensuring optimal performance for most usage scenarios [[1]] [[2]].
You can customize the filesystem parameters if needed, but the default options are generally sufficient for typical use cases [[1]].
Creating a Mount Point
Create a directory to serve as the mount point for the virtual disk:
bash


sudo mkdir /mnt/vdisk
This directory will be used to access the contents of the virtual disk.
Mounting the Virtual Disk
Finally, mount the virtual disk using:
bash


sudo mount -o loop vdisk.img /mnt/vdisk
Explanation of the Command
The -o loop option allows you to mount a file as if it were a disk. This is particularly useful for virtual disks created from image files.
Now, you can access the contents of your virtual disk at /mnt/vdisk.

File Compression and Packaging in Linux

Josh — Thu, 12 Dec 2024 12:28:27 +0000

Working with File compression and packaging.

tar -cvf myarchive.tar mydir/ # -c Create, -v Verbose, -f File
tar -tvf myarchive.tar # lists whats in your tar archive
tar -xvf myarchive.tar -C mynewdir # Extract your tar. -x Extract, -v Verbose, -f File, -C change to directory before extracting.

gzip myarchive.tar # will create you a myarchive.tar.gz
or 
tar -czvf myarchive.tar.gz /path/to/extract

tar -xzvf myarchive.tar.gz -C /path/to/extract # -x Extract, -z Uncompress

Tar - used for packaging files and directories together
gzip, bzip2, xz - is used for compressing

zip -r myarchive.zip /myarchive 
unzip -d /path/to/unzip/unzipped myarchive.zip

Linux Environment Variables

Josh — Wed, 11 Dec 2024 21:46:13 +0000

Environmental Variables: Variables that are available to your shell. they can be used in scripts that are run from the shell.



# View list of all your environment variables.
env

# This shows paths for all executable programs:
echo $PATH

# Create your own environmental variable:
export MY_ENV_VAR="My custom environmental var"
# Check if it worked using grep:
env | grep MY_ENV_VAR

# Make permanent variables
vi ~/.zshrc
# Now add your custom variables in
export MY_ENV_VAR="My custom environmental var"
export PATH="$PATH:$HOME/bashscripts"
# Then run this to take affect instead of restarting your terminal
source ~/.zshrc

# Remove variable
unset MY_VAR

Linux User Account Management

Josh — Wed, 11 Dec 2024 01:10:02 +0000

User account management cheat sheet



sudo useradd joshua  # create user
sudo useradd -m -d /home/customhome joshua # create user with custom home directory
sudo useradd -s /bin/bash joshua # create user with shell


# Password:
sudo passwd joshua # Set password for joshua
sudo passwd -l joshua # Locks account
sudo passwd -u joshua # Unlocks account

#User Modify
sudo usermod -aG developers joshua # adds joshua to developers group
sudo usermod -d /home/newhomedir joshua # Gives joshua new home directory
sudo usermod -aG sudo joshua # adds joshua to sudo group

# Change Shell
sudo usermod -s /bin/bash joshua

# Delete user account
sudo userdel -r joshua # -r deletes their home directory as well.

# Switch users
su - joshua

# List users groups
groups

Text Processing & Regular Expressions

Josh — Tue, 10 Dec 2024 20:55:44 +0000

Grep

grep "keyword" file.txt
grep "^keyword" file.txt # ^ will find your keyword that starts with the line
grep -i "keyword" file.txt # Makes it case insenstive
grep -n "keyword" file.txt # returns back which line your keyword was found.
grep -C 1 "keyword" file.txt # Gives the line before and the line after your keyword.
grep -v "someword" file.txt # Gives back patterns that dont match yours.
grep "Dev[To]*" file.txt # Finds all dev and devto and devt etc.
grep "^[1234567890]" file.txt # finds all lines starting with a number.
grep "[@qwertyuiopasdfghjklzxcvbnm].com" file.txt # finds all emails.

SED

sed 's/Yo/Sup/' file.txt # Replaces first occurrence of Yo with Sup.
sed 's/Yo/Sup/g' file.txt # Replaces all matching on each line.
sed -i's/Yo/Sup/g' file.txt # This will modify the file. The other ways only modify what is show in the terminal.
sed '3d' file.txt # Deletes the 3rd line in the file
sed '1i\First line' file.txt # Adds the text "First line" to the file.txt
sed '$a\Last line' file.txt # Adds the text "Last line" to end of the file.
sed -e 's/Yo/Sup/g' -e 's/joshua/Joshua/g' file.txt # -e allows for mutiple commands.
sed 's/[Ww]orld/Galaxy/g' file.txt # RegEx finds any World or world and replaces with Galaxy.

AWK

awk '{print $1}' file.txt # Prints the first word of each column
awk '{print $1, $2}' file.txt # Prints the first and second word of each line
awk '$2 > 28 {print $1 " is over 20"}' file.txt # Looks at second word of each line and compares it to see if its greater than 28 then print it.
awk 'NR > 1 {sum += $2} END {print "Average age:", sum/(NR-1)}' awk_test.txt # Checks if name records is greater than 1.

System has not been booted with systemd as init system (PID 1).

Josh — Mon, 09 Dec 2024 22:50:10 +0000

If you get a

System has not been booted with systemd as init system (PID 1). Can't operate.
Failed to connect to bus: Host is down

this typically occurs when you're trying to use the systemctl command in an environment that does not support systemd as the init system.

Solution: Use Sysvinit

# Use the Below
sudo service start <service name> 

## Example below
sudo service start nginx

# Instead of 
sudo systemctl start <service name>

Linux Permissions

Josh — Mon, 09 Dec 2024 22:27:54 +0000

View file permissions:

ls -l file.txt
ls -ld mydir/ # Checks permissions on directory
ls -lR mydir/ # List permissions of files in dir

Set Ownership

chown root:root file.txt
chown -R root:root mydir/  # Makes everything in mydir to be owned by root

Examples of permissions and what they mean:

-rw-rw-r-- 1 root root  0 Dec 10 05:38
#
# - this is a regular file.
# rw- represent the owner's permissions.
# rw- group.
# r-- others.

Permissions:

r (read): 4
w (write): 2
x (execute): 1

Examples:

chmod 777 file.txt
chmod 650 file.txt

Beginner Linux Commands

Josh — Sat, 07 Dec 2024 14:42:49 +0000

Display Current User:

whoami

Get Current user UID - User ID, GID - Group Primary ID, Groups - Groups you belong too.

id

System Monitoring:
Install htop and run it.

sudo apt install htop
htop

htop displays your systems performance. At the bottom of htop shows how you can use htop such as : search, filter, kill, etc. To exit htop just press q.

Show your current directory:

pwd

Show path to home directory:

List directories and files in your current directory:

ls

Create empty a file

touch file.txt

Create file with text in it:

echo "Hello World" > file.txt

Create a hidden file using the . :

echo "This file is hidden" > .cantsee

Display all files even hidden ones:

ls -a

Create a copy of file:

cp myfile.txt myfilecopy.txt

Copy to another directory:

cp myfile.txt newdirectory/

Moving files and changing name:

mv myfile.txt movedfile.txt

Move to new dirctory:

mv myfile.txt somedirectory/

Change name of directory:

mv somedirectory newnamedirectory

Move and rename one time:

mv somedir/myfile.txt ./somefile.txt

Remove a file:

rm file.txt

Remove empty directory:

rmdir somedir

Remove directory and all inside it:

rm -r somedir

Remove with prompts to confirm removal:

rm -i file.txt

Remove with recursive and force. Be careful with this command!

rm -rf somedir

Read file contents with cat

cat file.txt

Read file contents numbered

cat -n file.txt

Print the beginning of a file:

head # shows the first 10 lines
head -n1 file.txt  # -n1 prints the first line
head -c1 file.txt # -c1 prints the first character

print the last content of the file:

tail file.txt# shows last 10 lines
tail -n1 file.txt # -n1 prints the first line

See difference between 2 files:

diff myfile1 myfile2

diff -r ~/Downloads ~/Documents  # Directory diff with -r for recursive

Setting up WHM on Rocky 9 VPS

Josh — Wed, 04 Dec 2024 22:07:35 +0000

First I'll set up host name that matches my domain name:

hostnamectl set-hostname server01.pokeboost.net

Next I'll disable my firewall on my server as its required for WHM and cPanel installations.

Below appears that there is no firewall service on my vps so i can skip this. Later i will add a firewall.

[root@my-vps ~]# systemctl status firewalld.service
Unit firewalld.service could not be found.

Next i'll disable SELinux:

vi /etc/selinux/conf - Changed SELINUXTYPE=disabled

reboot

Next i will install Perl

yum install perl -y

Now we can finally download and install the software

cd /home && curl -o latest -L
https://securedownloads.cpanel.net/latest && sh latest

Make sure that you have curl before running that command as you can see i didn't have it.

yum install curl -y

After installation it should have a link to click, Following the link from the terminal.

( I got a timed out when i visited the link because my VPS didn't have a firewall but my provider Ionos has a cloud panel where you have to open the ports up. So i added 2087 and 2082 port in my firewall policy:

yum install curl -y

After installation it should have a link to click, Following the link from the terminal.

( I got a timed out when i visited the link because my VPS didn't have a firewall but my provider Ionos has a cloud panel where you have to open the ports up. So i added 2087 port in my firewall policy:

Then i logged in with my Linux server root credentials: root and root password.

Now we have successfully installed WHM cPanel on rocky Linux 9.

DNS / Hostnames:

Add A record to my server: I use the same hostname as i named my server.

Now i will add my default ionos name servers to my WHM account. Here is ionos default nameservers that i will add

Set the name servers and configure records.

You have completed installing and configuing DNS to work with your new WHM.

Set Static IPv4 on AlmaLinux

Josh — Wed, 04 Dec 2024 15:29:05 +0000

Step 1: Identify Your Network Interface
First, you need to find the name of your network interface. You can list all network connections with:

nmcli connection show
Mine was enp0s3

Step 2: Configure the Static IP Address

To set a static IP address, use the following command, replacing with the name of your connection, and adjusting the IP address, gateway, and DNS as needed:
bash

sudo nmcli connection modify <your_connection_name> ipv4.addresses 192.168.12.100/24 sudo nmcli connection modify <your_connection_name> ipv4.gateway 192.168.12.1 sudo nmcli connection modify <your_connection_name> ipv4.dns 8.8.8.8 sudo nmcli connection modify <your_connection_name> ipv4.method manual

Reference for above:
ipv4.addresses: Set this to your desired static IP address and subnet mask (e.g., /24 for 255.255.255.0).

ipv4.gateway: Set this to your network's gateway.

ipv4.dns: You can specify one or more DNS servers (e.g., Google's DNS 8.8.8.8).

ipv4.method manual: This tells NetworkManager to use a static IP configuration.

Step 3: Bring the Connection Up

After modifying the connection settings, you need to bring the connection down and then back up to apply the changes:

sudo nmcli connection down <your_connection_name> sudo nmcli connection up <your_connection_name>

Step 4: Make sure everything is correct

To confirm that your static IP address has been set correctly, you can check the current IP configuration with:

nmcli device show <your_interface_name>