Users and user groups for Linux

1, above this colorful picture, from Linxu under the etc/passwd file.

Let's take a detailed look at what these things are worth, which are separated by colons.

2, Etc/shadow

3, compare the permissions of the two files, why one is 644, and the other is 000. Can think for a moment.

After the user has finished, look at the permissions file for the user group. In fact, the user group permissions files and users are similar.

1, Etc/group

or separated by a colon.

The first bit is the group name.

The second bit is the password bit, which is the password for the group, and, like the user, there is a file dedicated to storing the group's password. Etc/gshadow

The third bit is the group ID of the user group

The fourth bit is an additional user in the user group.

2, just said, the group's password is stored in the Etc/gshadow.

The first bit is the user group group name

The second bit is the user group password, the default is empty, because the actual application, is basically not set.

The user name of the third-group administrator. The default is empty.

Fourth bit: Additional users in the group.

3, the user's mailbox var/spool/user name

var is the abbreviation of the English word variability "changeable, changeful". The variable is declared with Var in JS.

The Var directory generally places dynamic, often changing files. So the mail is here.

Spool is the coil, winding meaning. Spool also becomes a queue folder.

Users and user groups for Linux