新手必学：Ubuntu文件权限管理基础
Ubuntu文件权限管理是系统安全基础，通过控制三类主体（所有者、所属组、其他用户）的三类权限（读r、写w、执行x）实现。权限有字符（如rwxr-xr--）和数字（r=4,w=2,x=1，如754）两种表示方法。 查看权限用`ls -l`，第一列即权限信息；修改权限用`chmod`（符号模式如`u+x`或数字模式如`755`），`chown`/`chgrp`可改所有者/组。 注意：目录需执行权限（x）才能进入，文件默认权限644、目录755；避免777权限，关键文件用`chmod`和`chown`时加`sudo`。掌握基础权限即可应对日常需求，需注意安全原则并多实践。
Read MoreLinux User Permission Management: Resolving Common Issues for Beginners
This article introduces the basics of Linux permission management and solutions to common problems for beginners. The permission system can be analogized to an apartment building: users (residents), groups (families), and files/directories (rooms). Permissions include read (r=4), write (w=2), and execute (x=1). Common problem solutions: 1. Password reset: For regular users, administrators use `passwd` to change passwords. To reset the root password, enter single-user mode (add `init=/bin/bash` to Grub under CentOS, then execute `passwd root`). 2. Insufficient sudo privileges: Switch to root with `su -`, then use `visudo` to add the user's permission line. 3. Permission format parsing: For example, `-rw-r--r--` (regular file, owner can read/write, group/others only read). Modify permissions using `chmod` (numerical method like `755`, symbolic method like `u+x`). 4. Directory access denied: Execute permission is required. Use `chmod +x` or `chown` to change the owner/group. 5. Create user groups: Use `useradd`/`adduser` and `groupadd`, then `usermod -g/-G` to assign groups. Security prompt: Principle of least privilege, `
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