Linux users, Groups, permissions

Users, Groups, permissions

Security context (Secure):

Permissions:

R,w,x

File:

R: Readable, you can use similar commands such as cat to view the contents of the file;

W: writable, can edit or delete this file;

X: Executable, exacutable, can be submitted to the kernel at the command prompt as a command to run;

Directory:

R: LS can be executed on this directory to list all internal files;

W: Files can be created in this directory;

X: You can switch to this directory using a CD, or you can use Ls-l to view the details of the internal files;

0---: No permissions

1 001--x: Execution

2 010-w-: Write

3 011-wx: Write and Execute

4 r--: Read-only

5 101 R-x: Read and Execute

6 rw-: Reading and writing

7 111 rwx: Read and write execution

Users: UID,ETC/PASSWD

Group: Gid,etc/group

Shadow Password:

Users:/etc/shadow

Group:/etc/gshadow

User Category:

Admin: 0

Normal Users: 1-65535

System users: 1-499

General Users: 500-60000

User groups:

Administrators group

Normal Group:

System Group

General Group

User group Type:

Private group: When a user is created, a group with the same name as the user name is automatically created if the group to which it belongs is not specified

Basic group: Default group for users

Additional groups, additional groups: groups other than the default group

/etc/paswd (config file)

Account: Login Name

Password: password

UID: User ID

GID: Basic Group ID

GECOS: Notes

Home dir: Home directory

Shell: User's default shell

/etc/shadow (password config file)

Account: Login Name

Encrypted Password: encrypted password

Encryption method:

Symmetric encryption: Encrypt and decrypt using the same password

Public Key cryptography: each password appears in pairs, one for the private key (secret key) and one for the public key

One-way encryption, hash encryption: Extracting data signatures, often used for data integrity checks

1. Avalanche effect

2, fixed-length output

Md5:message digest,128 bit fixed-length output (Information Digest)

Sha1:secure Hash algorithm,160 bit fixed length output

Add User: Useradd

Useradd USERNAME

Password USERNAME password

Add Group: Groupadd Group

User management:

Useradd, Userdel, Usermod, passwd, Chsh, CHFN, finger, ID, chage Group management:

Groupadd, Groupdel, Groupmod, gpasswd

Rights Management:

Chown, Chgrp, chmod, umask

Linux users, Groups, permissions