Linux users, groups, and permissions

Because the operation of the file needs to switch to the appropriate folder, so the modification of the contents of the file, the most basic is the need for their folder execution permissions.

Read permissions for a folder can be exercised independently, but write permissions on the contents of the folder (new, deleted, renamed), like files within it, need to have the Execute permission (execute) of the folder first.

Contents of several important folders:

/etc/passwd file	root :x : 0:0 : root : /root : /bin/bash user name   password placeholder (with password x , no password is empty): uid : Group GID : User's description information (can not): User's home directory: /bin/bash or /sbin/nologin (open a terminal / cannot open terminal)
/etc/shadow	Store passwords for all users, each user occupies a single row of records, which is actually the database that holds the user's password (database ) Username: password, this password is a password that has been encrypted by md5 encryption algorithm.
/etc/group	wheel:x:10:egon,user1,user2 stored linux The information for all groups in the system, which is actually a database that holds group information (database ) Group name: x means that this group is logged in linux The system must use a password: the gid : The group member is logged.
/etc/gshadow	Group Password
/home/user1	User home directory
/var/spool/mail/user1	User Mailbox

Knowing the purpose of the above folder, you can manually create a user, as follows:

Create a user named Alex, which involves copying the basic settings in one step, because the owner and the genus of the files are copied directly, so the user who performs the replication behavior needs to be changed.

Another: Update linux common Command table (new tab open See larger image)

Linux users, groups, and permissions