User and group management

 user and group management:

useradd spiderman: add the new user called spiderman

groupadd superheros create the group called superheroes. cat /etc/group: shows the list of groups and its members.

userdel -r spiderman: delete the user spiderman.

groupdel superheroes: deletes the group superheroes.

usermod -G superheroes superman change the group of superman to superheroes. 

chgrp -R superheroes spiderman: change the group of spiderman to superheroes.

cat /etc/passwd: gives the local accounts output.

output format of /etc/passwd file: username: password: userid: groupid: home directory: shell type.

output format of /etc/group file: groupname:x: groupid: groupmembers.

useradd -g linux_admins -s /bin/bash -c "sadik pathan" -m -d /home/admin_spathan admin_spathan: add the

username admin_spathan in linux_admins group. 

passwd admin_spathan: create the passwd for admin_spathan

chage -m 5 -M 90 -w 10 babubutt  : after the password change, babubutt is not allowed to change the password for 5 days, password will expire after 90 days and before 10 days of password expires, password expiry notification will come.

chage -l babubutt: gives the password information for user babubutt.

ip r l: gives the ip address of the machine.

..................................................

control the access of the files:

chmod g-w filename: removes the write access for group on file named filename.

chmod a-r filename: removes the read acess for all(user group and others) on the file named filename

chmod u-w filename: removes write access for user in file named filename.

rm filename: removes the filename

chmod u+rw file: gives the read write access to user on the file chmod g+rw file: gives the read write access to group on the file.

chmod o+r file: gives read access to others on the file.

chmod a-x folder: removes the execute permission for all on the folder.

chmod a+x folder: gives the execute permission for all on the folder.

chown: change the ownership of the file. chgrp: change the group ownership of the file.

chown root file: change the owner to root for file.

chgrp root file: change the group ownership to root for the file.