Linux Basic Command
Disk usage,
tar command to Compress and Extract Files
Here’s what those flags (-cvf) actually mean-c, --create
– create a new archive-x, --extract, --get
– extract files from an archive-f, --file ARCHIVE
– use archive file or device ARCHIVE
Now see the file
Create a new archive
now see new archive created
Now extract file; no normal directory found
Now extract Desktop dir
Gzip compression
Extract gz file
Remove a .gz file
Grep
grep installation
Search word hi
Case insensitive search: The -i option enables to search for a string case insensitively in the given file. It matches the words like “UNIX”, “Unix”, and “unix”.
See the content 1.txt
Display a matching word
Display a matched word line number
Display a matched words
Display a ending with letter a
Display a matched letter without case sensitive -i [a-c]
word count
Display a line without hi
Search by word
Ethernet down
Ethernet up
Date
Set date
View last Sunday's date
Calendar
Display current month
Display a specified month
Display a 5month of 2024
Display 2024
display current month,previous,before month
Word count
Count line, words,letters
Count word
Count letters
Count line
How to create, delete, and modify groups in Linux
Groups are an essential part of the Linux permission structure and a powerful way to manage file access on your system.
know groups command groups
cat /etc/group/
To add a group in Linux, use the groupadd
command:
sudo groupadd java
You can verify that the group appears (and see its group ID) by looking in the /etc/group
file.
now java group added
If you want to create a group with a specific group ID (GID), use the --gid
or -g
option:
sudo groupadd -g 1009 demo1
Change the group ID
sudo groupmod -g 1012 demo1
Rename a group
sudo groupmod -n test demo1
before see the group id for demo1
now will be changing
See the groups
Now see the same group id changed from demo1 to test
Add and remove users from a group
Suppose you have existing users named user1 and user2, and you want to add them to the demo group. Use the usermod
command with the --append --groups
options (-a
and -G
for short):
sudo usermod --append --groups demo user1
sudo usermod -aG demo user2
Look in the /etc/group
file or use the id
command to confirm your changes:
id user1
Add a user
Delete a user
Delete a group
sudo groupdel user1
SSH
sudo apt-get install openssh-server
sudo service ssh status
edit sshd_config file
sudo vi /etc/ssh/sshd_config
Head and tail command
The head is used for displaying the first 10 lines of the file
tail is used for displaying the last 10 lines of the file
First see test1 file content
reading from firstline
Read a first line
show the first 3 lines
shows the multiple files
tail command
Normal fiel view
Read from last line tail file.txt
tail -n1 file.txt
It display last three lines
tail file.txt file2.txt
How to find IP address
ip address
hostname -i
ip a
ip add
ifconfig
Now see the file test1
remove a test1 file
Now see test1 not found
Remove morethan one file
list
remove a 1 2
now see found not found 1 2
Create a directory
now see sun directory has created
Remove a directory
now see sun directory not found
Create a directory inside ; this means b directory created inside a directory
Now see b directory created inside a
Delete a inside directory
Options: 1. -i (Interactive Deletion): the -i option makes the command ask the user for confirmation before removing each file, you have to press y for confirm deletion, any other key leaves the file un-deleted.
-f (Force Deletion): rm prompts for confirmation removal if a file is write protected. The -f option overrides this minor protection and removes the file forcefully.
find used to search a file in the directory
Now see 1.txt file found in a directory, So we using find command
Find files created in last 7 days
Find files created last 60 minutes
find files in last 20 days with above 5MB
To make the command case insensitive you need to use iname instead of name . Command