Practical Linux - Part 07 - User/Permission System | 用户与权限系统

Oct 14 - User/Permission System
- http://linux.vbird.org/linux_basic/0410accountmanager.php
- Steps to setup text mode on boot: http://ubuntuhandbook.org/index.php/2014/01/boot-into-text-console-ubuntu-linux-14-04/
- uid & gid
  - Linux knows id not name
- /etc/passwd
  - username:password:uid:gid:description:home_dir:shell
- /etc/shadow
  - username:hashed_password:modification_date:…
- /etc/group
  - groupname:gpassword:gid:groupuser
  - initial group - gid in /etc/passwd
  - effective group - egid - e.g. create file
- ACL
- switch user
  - reasons
    - good habit
    - limit permission
    - some programs do not support root
- user shell
  - /sbin/nologin
- user info
  - last
  - w / who
  - wall - broadcast
- commands
  - users - show
  - useradd - add
    - -D default value
  - adduser - add
  - passwd - modify
    - root can reset password
  - usermod - modify
  - userdel - delete
  - groups
  - newgrp - change egid
  - groupadd
  - groupmod
  - groupdel
  - su -
  - sudo <command>
    - interval
  - visudo - /etc/sudoers
- Assignment
  - log on your amazon vm
  - create a new user ‘oct14’
  - create a new group ‘ftpusers’
  - add user ‘oct14’ into group ‘ftpusers’ (also keep the original group of the user)
  - switch user to root
  - use touch command to create a new file in /root

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