Linux commands

Advanced Linux Commands

System Monitoring and Performance

1. top - Displays real-time system processes and performance information.

1 top

2. htop - An interactive process viewer, similar to top , but with a more user-friendly interface.

1 htop

3. iostat - Reports CPU and I/O statistics.

1 iostat

4. vmstat - Reports virtual memory statistics.

1 vmstat

5. nmon - Performance monitoring tool for Linux.

1 nmon

Networking

1. ifconfig - Displays or configures network interfaces.

1 ifconfig

2. ip - Shows/manipulates routing, devices, policy routing, and tunnels.

1 ip a
2 ip r

3. netstat - Displays network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

1 netstat -tuln

4. ss - Utility to investigate sockets.

1 ss -tuln

5. tcpdump - Captures and analyzes network traffic.

1 tcpdump -i eth0

6. nmap - Network exploration tool and security/port scanner.

1 nmap -A 192.168.1.1

Disk Usage and Management

1. df - Reports file system disk space usage.

2. du - Estimates file space usage.

1 du -sh /path/to/directory

3. lsblk - Lists information about all available or the specified block devices.

1 lsblk

4. blkid - Locates/prints block device attributes.

1 blkid

5. lsof - Lists open files.

1 lsof +D /path/to/directory

File Operations

1. rsync - Fast, versatile, remote (and local) file-copying tool.

1 rsync -avz /source/directory/ user@remote:/destination/directory/

2. tar - Archives multiple files into a single file and extracts files from an archive.

1 tar -cvf archive.tar /path/to/directory

3. find - Searches for files in a directory hierarchy.

1 find /path/to/search -name "filename"

4. grep - Searches for patterns in files.

1 grep -r "search_term" /path/to/directory

5. awk - Pattern scanning and processing language.

1 awk '{print $1}' file.txt

6. sed - Stream editor for filtering and transforming text.

1 sed -i 's/old_string/new_string/g' file.txt

User and Permissions Management

1. chown - Changes file owner and group.

1 chown user:group filename

2. chmod - Changes file modes or Access Control Lists.

1 chmod 755 filename

3. usermod - Modifies a user account.

1 usermod -aG groupname username

4. sudo - Executes a command as another user.

System and Process Management

1. systemctl - Manages systemd services.

1 systemctl start/stop/restart/status service_name

2. journalctl - Queries and displays messages from the journal.

1 journalctl -u service_name

3. crontab - Schedules periodic background jobs.

1 crontab -e

4. at - Schedules commands to run at a particular time.

1 at 14:00

5. screen - Terminal multiplexer that allows for persistent sessions.

1 screen

6. tmux - Terminal multiplexer, an alternative to screen .

1 tmux

Security and Access Control

1. ufw - Uncomplicated Firewall, a frontend for iptables.

1 ufw allow/deny port

2. fail2ban - Bans IPs that show malicious signs.

1 fail2ban-client status

3. ssh-keygen - Generates, manages, and converts authentication keys for SSH.

1 ssh-keygen -t rsa

4. gpg - Encrypts and signs data and communications.

1 gpg --gen-key
2 gpg --encrypt --recipient user@example.com file.txt

Package Management

1. apt-get (Debian/Ubuntu) - Command-line tool for handling packages.

1 sudo apt-get update

2. yum (CentOS/RHEL) - Package manager for RPM-based distributions.

1 sudo yum update

1 sudo dnf update

4. snap - Universal package management system.

1 sudo snap install package_name

System Information and Configuration

1. uname - Prints system information.

1 uname -a

2. hostnamectl - Controls the system hostname.

1 hostnamectl set-hostname new_hostname

3. timedatectl - Controls the system time and date.

1 timedatectl set-time "YYYY-MM-DD HH:MM:SS"

4. lsmod - Shows the status of modules in the Linux Kernel.

1 lsmod

5. modprobe - Adds or removes modules from the Linux kernel.

1 sudo modprobe module_name

File Systems and Disk Management

1. mkfs - Builds a Linux file system on a device.

1 sudo mkfs.ext4 /dev/sdX1

2. fsck - Checks and repairs a Linux file system.

1 sudo fsck /dev/sdX1

3. mount - Mounts a file system.

1 sudo mount /dev/sdX1 /mnt

4. umount - Unmounts a file system.

1 sudo umount /mnt

5. dd - Converts and copies a file.

1 sudo dd if=/dev/sdX of=/path/to/backup.img bs=4M

Advanced Networking

1. traceroute - Tracks the route packets take to a network host.

1 traceroute google.com
2. mtr - Combines the functionality of traceroute and ping .

1 mtr google.com

3. iptable - Linux firewall and NAT tool.

1 sudo iptables -L
2 sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT

4. curl - Transfers data from or to a server.

1 curl -O <http://example.com/file.txt>
2 curl -X POST -d "param1=value1&param2=value2" <http://example.com/resource>

5. wget - Non-interactive network downloader.

1 wget <http://example.com/file.txt>

Advanced Process Management

1. nohup - Runs a command immune to hangups.

1 nohup command &

2. nice - Runs a command with a modified scheduling priority.

1 nice -n 10 command

3. renice - Alters the priority of running processes.

1 sudo renice -n 10 -p PID

4. xargs - Builds and executes command lines from standard input.

1 cat file.txt | xargs -n 1 -P 4 command

5. pkill - Signals processes based on name and other attributes.

1 pkill -9 process_name

User and Group Management

1. groupadd - Adds a new group to the system.

1 sudo groupadd group_name

2. usermod - Modifies a user account.

1 sudo usermod -aG group_name user_name

3. passwd - Changes a user's password.

1 sudo passwd user_name

4. chage - Changes the user password expiry information.

1 sudo chage -l user_name

1. cron - Schedules jobs to run periodically at fixed times, dates, or intervals.

1 crontab -e
2 # Add a new cron job:
3 # * * * * * /path/to/script.sh

2. at - Schedules commands to run once at a specified time.

1 echo "command" | at 10:00

3. inotifywait - Watches for changes to files and directories.

1 inotifywait -m /path/to/watch

4. expect - Automates interactive applications.

1 expect script.exp