linux – user, group and file permissions

users:

A user is account to login and own files/process in linux

Types of users:

• root user: superuser having full access
• system user: created user for services EX: mysql, sql, oracle, tomcat
• Regular : Human account – people login to linux

whoami - this will give user which is currently active

useradd - ```sudo useradd devloper``` - low level user

password - create password for user ```sudo passwrd devloper```

adduser  - interactive action ```sudo adduser qt-admin```

su username - switch to users ```sudo su qt-admin```

Group – collection of users and provide permissions to file and directories.

• groups – show all groups in linux machine specific user

• create group sudo groupadd dev

• cat /etc/group – show all groups

• Add user to specific group- sudo usermod -aG dev qt-admin

• groupdel stg – delete group

• sudo gpasswd -d username groupname ex: sudo gpasswd -d qt-admin dev

File permissions

-rw-r–r– 1 root root 5684 Jul 24 02:03 logfile.txt

• type of file ex: – is file, d is directory , l -link (soft/hard)

rw- first will be user permissions root (user)

r– group permissions ex: dev, admin, qa (group)

r– others

permissions in linux files

• read -r
• wirte -w
• excute- x

two ways provide acces

symbolic method

user – u group -g other -o

• sudo chmod u+x filename – give execute permissions to user

• sudo chmod ugo+x – provide excute access for all

• sudo chmod ugo+xrw logfile.txt – add full permissions

• sudo chmod go-w logfile.txt – remove permissions

• sudo chmod -R u+rwx,g+rx,o+r src – provide different access ugo

Numeric method

read – 4

wirte – 2

excute – 1

no access – 0

• user -rwx, group- rx , other -x

4+2+1, 4+1, 1 = 751

sudo chmod 751 filename

Task:

• create 10 users and 2 groups
• create files and give group permissions
• check acccess for file