File Operations: Copy, Move, and Delete

In Linux systems, the fundamental commands for file manipulation are cp (copy), mv (move), and rm (remove). ### Copy Command (cp)

The cp command follows this syntax: ``` cp [-adfilprsu] source_file destination_file cp [options] source1 source2 source3 ... directory

Key parameters include: - `-a`: Archive mode, preserves all directory attirbutes
- `-d`: Copies symbolic links as links rather than the files they point to
- `-f`: Force mode, overwrites existing files without prompting
- `-i`: Interactive mode, prompts before overwriting existing files
- `-l`: Creates hard links instead of copying files
- `-p`: Preserves file attributes and timestamps
- `-r`: Recursive copy, used for directories
- `-s`: Creates symbolic links (shortcuts)
- `-u`: Updates only if the destination file is older than the source

Example: To copy `/data/source.txt` to `/backup/destination.txt`: ```
cp /data/source.txt /backup/destination.txt

Move Command (mv)

The mv command syntax is: ``` mv [-fiv] source destination

Parameters: - `-f`: Force mode, moves files without prompting
- `-i`: Interactive mode, prompts before overwriting existing files
- `-u`: Updates only if the destination file is older than the source

Example: To move `/home/user/docs/report.pdf` to `/shared/reports/`: ```
mv /home/user/docs/report.pdf /shared/reports/

Delete Command (rm)

The rm command syntax: ``` rm [-fir] files_or_directories

Parameters: - `-f`: Force mode, deletes without confirmation
- `-i`: Interactive mode, prompts before each deletion
- `-r`: Recursive mode, used for deleting directories and their contents

Example: To remove `/tmp/old_files` directory: ```
rm -rf /tmp/old_files

Firewall Configuration

Linux systems use firewalld as the default firewall management tool. Key commands include: ### Firewalld Service Management

# Check firewall status
systemctl status firewalld

# Install firewalld if not present
yum install firewalld

# Start the firewall service
systemctl start firewalld.service

# Stop the firewall service
systemctl stop firewalld.service

# Restart the firewall service
systemctl restart firewalld.service

# Disable firewall at boot
systemctl disable firewalld.service

# Enable firewall at boot
systemctl enable firewalld.service

# Check if service is enabled at boot
systemctl is-enabled firewalld.service

Firewall Rule Management

# Check firewall version
firewall-cmd --version

# Display firewall status
firewall-cmd --state

# List all open ports
firewall-cmd --zone=public --list-ports

# Add a permanent port rule (example: port 80/tcp)
firewall-cmd --zone=public --add-port=80/tcp --permanent

# Remove a port rule
firewall-cmd --zone=public --remove-port=80/tcp --permanent

# Reload firewall rules
firewall-cmd --reload

# View active zones
firewall-cmd --get-active-zones

# Check interface zone assignment
firewall-cmd --get-zone-of-interface=eth0

# Enable panic mode (blocks all traffic)
firewall-cmd --panic-on

# Disable panic mode
firewall-cmd --panic-off

# Check panic mode status
firewall-cmd --query-panic

File Transfer Operations

For file transfer between Linux and Windows systems, install the lrzsz package: ``` yum install -y lrzsz

Key commands: - `rz`: Upload files from Windows to Linux
- `sz filename`: Download files from Linux to Windows

Archive and Compression
-----------------------

The `tar` command is used for creating and extracting archives. Common parameters include: - `-c`: Create a new archive
- `-x`: Extract files from an archive
- `-t`: List archive contents
- `-z`: Compress/decompress with gzip
- `-j`: Compress/decompress with bzip2
- `-v`: Verbose mode (show files being processed)
- `-f`: Specify archive filename

### Creating Archives

Create a simple tar archive

tar -cvf /backup/etc.tar /etc

Create a gzipped tar archive

tar -zcvf /backup/etc.tar.gz /etc

Create a bzip2 compressed tar archive

tar -jcvf /backup/etc.tar.bz2 /etc

Create a compress compressed tar archive

tar -Zcvf /backup/etc.tar.Z /etc

### Extracting Archives

Extract a tar archive

tar -xvf archive.tar

Extract a gzipped tar archive

tar -xzvf archive.tar.gz

Extract a bzip2 compressed tar archive

tar -xjvf archive.tar.bz2

Extract a compress compressed tar archive

tar -xZvf archive.tar.Z

Extract RAR archives

unrar e archive.rar

Extract ZIP archives

unzip archive.zip

### Viewing Archive Contents

List contents of a tar archive

tar -tvf archive.tar

List contents of a gzipped tar archive

tar -ztvf archive.tar.gz

List contents of a bzip2 compressed tar archive

tar -jtvf archive.tar.bz2

List contents of a compress compressed tar archive

tar -Ztvf archive.tar.Z

File Linking Operations
-----------------------

Linux supports two types of file links: symbolic (soft) links and hard links. ### Symbolic Links

Symbolic links are created with the `-s` option. They act as pointers to the original file: ```
ln -s /usr/bin/python3 /usr/bin/python

Symbolic links: - Take minimal disk space

• Can link across different filesystems
• Can link to directories
• Can become "dangling" if the originla file is deleted

Hard Links

Hard links are created without the -s option: ``` ln /usr/bin/python3 /usr/bin/python_hard

Hard links: - Take the same amount of space as the original file
- Cannot link across different filesystems
- Cannot link to directories
- Directly reference the inode of the original file

Both types of links maintain synchronization with the original file - changes to either the link or the original file are reflected in all linked instances. File Searching
--------------

The `find` command is used to search for files based on various criteria: ```
find /path/to/search -criteria [value]

Common search criteria: - -type f: Search for files

• -type d: Search for directories
• -name pattern: Search by name (case-sensitive)
• -iname pattern: Search by name (case-insensitive)
• -size +100M: Search for files larger than 100MB
• -size -100M: Search for files smaller than 100MB
• -perm 755: Search for files with specific permissions

Example searches: ```

Find all .conf files in the system

find / -type f -name "*.conf"

Find all directories larger than 100MB

find / -type d -size +100M

Find files with specific permissions

find /tmp -perm 755

Find files and display details

find /var -size +100M -ls

Process Management
------------------

### Process Listing with ps

The `ps` command displays currently running processes: ```

# List all processes
ps -ef

# Filter processes (example: find Java processes)
ps -ef | grep java

# Find top 10 processes by memory usage
ps -auxf | sort -nr -k 4 | head -10

# Find top 10 processes by CPU usage
ps -auxf | sort -nr -k 3 | head -10

Java Process Management with jps

The jps command lists Java processes: ```

List Java PIDs and main class names

jps

List Java PIDs with full class names

jps -l

List Java PIDs with main classes and arguments

jps -lm

List Java PIDs with JVM arguments

jps -v

List Java processes with full details (similar to ps -ef | grep java)

jps -lvm

Log File Analysis
-----------------

Linux provides several tools for examining log files: ```

# Search for specific content in logs
grep 'error' /var/log/syslog

# View the last 100 lines of a log file and follow new entries
tail -f /var/log/application.log

# View the last 100 lines of a log file
tail -100 /var/log/application.log

# Search in compressed log archives
zgrep 'error' /var/log/syslog.1.gz

# Count occurrences of specific patterns
grep -c 'error' /var/log/syslog

Configuration File Editing

The vim text editor is commonly used for configuration files: ```

Open a configuration file

vim /etc/profile

Insert mode: Press 'i' to start inserting text

Exit insert mode: Press 'Esc'

Save and quit: Press ':', type 'wq', then press Enter

Quit without saving: Press ':', type 'q!', then press Enter

Apply changes to a profile file

source /etc/profile