1. Manage User and Permission
1.1. User
1.1.1. command
1.1.1.1. adduser sarveen
1.1.1.1.1. adduser -force SARVEEN
1.1.1.2. usermod -u 1001 sarveen
1.1.1.3. usermod -d /tmp/sarveen sarveen
1.1.1.4. useradd -G DDT4B sarveen
1.1.1.5. usermod -L -e 2020-03-02 sarveen
1.1.1.6. usermod -r sarveen
1.2. Group
1.2.1. command
1.2.1.1. groupadd DDT4B
1.2.1.1.1. groupmod -g 1111 DDT4B
1.2.1.2. groupmod -n DDT4B OSOS
1.2.1.3. groupdel DDT4B
1.3. Root
1.3.1. command
1.3.1.1. sudo passwd root
1.3.1.1.1. to change the password of root
1.3.1.2. su -c "adduser sarveen"
1.3.1.2.1. to apply command entitle root without entering root environment
2. Umask
2.1. umask 022
2.1.1. file default permission is 644
2.1.2. directory default permission is 755
3. R W X
3.1. rwx
3.1.1. read
3.1.1.1. 4
3.1.2. write
3.1.2.1. 2
3.1.3. execute
3.1.3.1. 1
3.2. method
3.2.1. alphabet
3.2.1.1. chmod 775 file01
3.2.2. numeric
3.2.2.1. chmod ug=rwx, 0+w file01
3.3. ugo
3.3.1. user
3.3.1.1. user is owner of the file
3.3.2. group
3.3.2.1. group that assigned in the file
3.3.3. others
3.3.3.1. other than user or group
4. Command
4.1. Chmod
4.1.1. Change Permission Value for File or Directory
4.1.1.1. chmod 775 file01
4.2. Chown
4.2.1. Change File or Directory Owner
4.2.1.1. chown osos file01
4.3. Chgroup
4.3.1. Change File or Directory Group
4.3.1.1. chgrp DDT4B file01