Disk Partition Analysis

To identify which partition a specific directory resides on, utilize the df command with the -h flag for human-readable output. For example, to determine the partition containing the /var directory:

[root@server ~]# df -h /var
Filesystem              Size  Used Avail Use% Mounted on
/dev/mapper/vg_system-lv_root   50G  3.1G   44G   7% /

The 'Mounted on' column indicates the partition location.

For a comprehensive view of all disk partitions, employ the fdisk command with the -l option:

[root@server ~]# fdisk -l

System Management Operations

Several commands are essential for system administration:

• sync: Writes all buffered data to disk
• ps -ef: Displays running processes
• netstat -tuln: Shows active network services
• shutdown: Powers down the system
• reboot: Restarts the system (use -h now for immediate restart)
• poweroff: Halts system and powers off
• init: Changes system runlevel

Text File Editing

The nano editor provides a simple interface for file manipulation:

• To save modifications: Press Ctrl+O
• To exit: Press Ctrl+X

File Permission Management

Modify file access permissions using chmod:

chmod 777 filename
chmod a+w filename

Additionally, change file ownership with:

• chgrp: Modifies group ownership
• chown: Changes user ownership

File Operations

Copy files with the cp command:

cp source_file destination_file

User Account Management

Create and manage user accounts with these commands:

useradd newuser
passwd newuser

Notes: New user accounts automatically create home directories in /home. Additional usermod options are available via usermod --help. Remove users with:

userdel newuser
rm -rf /home/newuser

Environment Variables

Display system or user environment variables:

echo $PATH

File Viewing Utilities

Various commands allow direct file content viewing:

• cat: Displays file content from beginning to end
• tac: Shows file content in reverse order
• nl: Numbers lines while displaying content

Storage Analysis

Monitor disk and directory usage with:

• df: Shows disk space utilization
• du: Displays directory space consumption

File Link Types

Understand the difference between link types:

• Hard links: Function as additional names for the same inode. Deleting one doesn't affect others as they share identical inode numbers.
• Soft links (symbolic links): Act as shortcuts to original files. If the target file is deleted, the soft link becomes a dangling link and unusable.

Important: Removing a soft link doesn't impact the original file, but deleting the original file creates a dangling link. If the original file is recreated with the same path, the dangling link can be restored.