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