Detailed Explanation of Linux File Permissions: Must-Know Knowledge for Beginners
Linux file permissions are the core of system security, controlling user access methods to prevent misoperations or data breaches. Files are associated with three types of users: the owner (highest authority), the associated group (shared within the group), and others. Permissions are divided into three categories: read (r=4), write (w=2), and execute (x=1). Permissions can be represented in two forms: symbolic (e.g., `rwxrwxrwx`, where the first character indicates the file type, and the next three groups represent permissions for the three user categories) and numeric (octal, where the sum of permissions for the three user categories gives the value, e.g., `755`). Proficiency in mutual conversion between these forms is required. File and directory permissions differ: for files, `r` = view, `w` = modify/delete, `x` = execute; for directories, `r` = list contents, `w` = create/delete, `x` = enter. To modify permissions, use `chmod` (in symbolic or numeric form with `-R` for recursive directory changes) and `chown` (to change owner/group). Special permissions (SUID/SGID/SBIT) are used for specific scenarios. Mastery of symbolic-numeric conversion, `chmod` usage, and the differences between file and directory permissions enables proficiency through practice.
Read MoreLinux System Maintenance: Essential Basic Knowledge for Beginners
Maintaining Linux servers is an essential skill in the internet era. Linux, being stable, open-source, and secure, is the mainstream operating system for servers. Beginners can solve common issues such as file permissions and service startup by mastering basic operations. Core skills include: command-line operations (ssh login, basic commands like pwd/ls/cd); file system (root directory and core directory structures such as /etc/var); file operations (touch/mkdir/cp/mv/rm); permission management (rwx permission representation, chmod modification); processes and services (ps/top/kill for viewing and terminating processes, systemctl for managing services); network configuration (ip addr, ping, port checking, and firewall setup); system updates (apt/yum for updates, software installation and uninstallation); and log backup (tar compression, tail for log viewing). Learning suggestions: practice extensively using virtual machines or experimental platforms, utilize tools like Xshell/FinalShell, make good use of the man command for help, back up data before operations, and develop a cautious habit.
Read MoreEssential Linux Command Line Tips for Beginners
This article introduces the learning and use of the Linux command line. The reason for learning the command line is its directness and efficiency, which is suitable for server management, can complete complex tasks, and is more flexible than the graphical interface. Basic file directory operations include ls (list directories, e.g., ls -la shows detailed hidden files), cd (change directory, e.g., cd ~ returns to the home directory), pwd (show current path), mkdir (create directories), touch (create empty files), rm (delete, e.g., rm -rf is used with caution), cp (copy), mv (move/rename), etc. It should be noted that dangerous operations such as rm -rf require special caution. Efficiency tips include: shortcuts (Ctrl+C to interrupt, Ctrl+D to exit, etc.), wildcards (* for batch file matching), pipes | to combine commands (e.g., ls | grep "txt"), background operation &, using --help or man to check help, history commands (history) and Ctrl+R for search. Common problem solutions: For insufficient permissions, use sudo to elevate privileges; check command spelling or consult help if there is an error; exit with exit or Ctrl+D. Summary: The command line is a set of tools that can be mastered with more practice. Platforms like Runoob and Learn Linux Terminal are recommended for learning.
Read MoreCommon Issues for Beginners: How to Troubleshoot Linux Service Startup Failures
Linux service startup failures are common issues for beginners. Here's a step-by-step troubleshooting guide: First, confirm the status with `systemctl status 服务名` (replace "服务名" with the actual service name); if it shows "failed", further investigation is needed. Next, use `journalctl -u 服务名` or service-specific logs (e.g., Nginx error log at `/var/log/nginx/error.log`) to identify errors, focusing on keywords like "syntax error", "port in use", or "permission denied". If the service is not installed, check with `yum list installed` (for RHEL/CentOS) or `dpkg -l` (for Debian/Ubuntu), then install it via `yum` or `apt`. Key areas to check include: configuration file syntax (e.g., `nginx -t` for Nginx), port conflicts (use `netstat -tuln` to check ports), dependent services (via `systemctl list-dependencies`), and permission issues (adjust ownership and file permissions). Following the order "status → logs → fix configuration/port/dependencies" and combining log analysis with command checks will help resolve issues quickly for beginners.
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