Linux 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, `
Read MoreLinux User Management: Creation, Deletion, and Permission Assignment
Linux user management is fundamental to system maintenance, distinguishing permissions through user (UID) and group (GID) identifiers to ensure security and resource isolation. Core operations include: User creation requires administrative privileges, using `useradd -m username` (-m creates a home directory) followed by `passwd username` to set a password. Viewing user information uses `id`, and switching users is done with `su -`. User deletion is performed via `userdel -r username` (-r removes the home directory). Permission management is achieved through `chmod` (letter/numeric method), `chown`/`chgrp` (change owner/group), with the `-R` flag for recursive directory permission changes. Temporary privilege elevation with `sudo` requires adding the user to the `wheel` (CentOS) or `sudo` (Ubuntu) group using `usermod -aG`. Caution is advised during operations to avoid accidental user deletion or incorrect permission assignments.
Read MoreEssential for Beginners: A Detailed Explanation of Linux User Permission Management
Linux permission management is the core of security and collaboration in multi-user systems, aiming to protect system security (preventing misoperations and malicious behaviors) and enable division of labor and collaboration (different users obtaining permissions as needed). Core concepts include three types of users (ordinary users, system users, root), user groups (for unified permission management), and file/directory permissions divided into three categories: owner, group, and others. Each category corresponds to three operations: read (r), write (w), and execute (x) (e.g., a directory requires x permission to be entered). To view permissions, use `ls -l`. To modify permissions, use `chmod` (numerical method: r=4, w=2, x=1; e.g., 754 represents rwxr-xr--; symbolic method: `+/-/=` to add/remove/set permissions, e.g., `u+x` adds execute permission to the owner). Ownership or group can be changed via `chown`/`chgrp`. Common issues to note: Files cannot be modified mostly due to permission or ownership problems; directories cannot be accessed without x permission; ordinary users use `sudo` to escalate privileges. Security recommendations: Minimize root usage, do not grant write permissions to others, and regularly check permissions. Master `ls -l`, `chmod`, and `chown`.
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