Basic concepts for Linux users and groups

(i) User, group and Rights management

• Multi-tasks,multi-user
• Per User:
  • User ID, password
    • 3 A
      • Certified/authentication
      • Authorized/authorization
      • Audit/audition
  • Group: User groups, user containers, sometimes called roles
• User class
  • administrator
  • Normal user
    • system user
    • login user
  • User id: userid,uid,1 6bits binary digits, valid range 0-65535
    • admin: 0
    • Normal User: 1-65535,centos, generally only to 60,000
      • system User: 1-499 (Cent OS6), 1-999 (CentOS7)
      • Normal User: 500-60000 (CentOS6), 1000-60000 (CentOS7)
    • User resolution: Name translation; The
      • username<-->uid
      • is based on the name resolution library:/etc/passwd
• Group
  • Group Category 1:
    • Administrators group
    • Normal user group
      • System user Group
      • login user Group
      /ul>
      • Group ID: groupid,gid,16bits binary number, valid range 0-65535
        • Administrators group: 0
        • Normal user group: 1-65535 for CentOS Generally, only 60,000
          • system Users Group: 1-499 (CentOS6), 1-999 (CentOS7)
          • Normal user group: 500-60000 (CentOS6), 1000-60000 (CentOS7)
        • name resolution
          • Groupname<-->gid
          • based on name resolution library: /etc/group
    • Group Category 2:
      • User's primary group/base group
      • User's additional group /li>
    • Group Category 3
      • user's private group: group name is the same as user name and contains only one user
      • public group: group contains multiple users
    li>
• Certification Information
  • Consistent with the information provided at the time of landing, by comparison to pre-stored
  • Password:
    • User password:/etc/shadow
    • Group Password:/etc/gshadow
    • Use Policy for passwords
      • Use random passwords
      • Minimum length not less than 8 bits
      • Use a minimum of three types of characters in uppercase letters, lowercase letters, data, and punctuation
      • Regular replacement
    • Encryption algorithm
      • Symmetric encryption: Encryption and decryption using the same key
      • Asymmetric encryption: Encryption and decryption using a pair of keys: Common key/pubic key, private key/private key
      • One-way encryption: can only encrypt, cannot decrypt; Extract data signatures
        • Fixed-length output, no matter how long the source plaintext
        • There are avalanche effects, and small changes in initial conditions can lead to dramatic changes in results.
        • echo "How is You?" | Md5sum
        • echo "How is You?" | Sha512sum

Basic concepts for Linux users and groups