Johnson

In Linux, the “ALL ALL=(ALL) ALL” grants full sudo privileges to all users on all hosts for all commands in the sudoers file.

The & wait $! notation allows scripts to run commands in parallel, wait for commands to complete, or perform actions based on the success or failure of commands.

To start/stop or enable/disable the firewalld services, execute the “sudo systemctl firewalld.service” command in Linux.

Users can monitor log files in real-time and keep tailing them even when the latest date of one changes by following the “tail [options] [log_file]” syntax.

The “cmake: command not found” error is fixed by installing the “Cmake” package or adding the Cmake binary to your PATH environment variable.

The “Nslookup: command not found” error occurs when the nslookup command is not installed. To install it, run the “yum install bind-utils” command.

In Linux, the “su -” is utilized to switch to a user account with a login shell session, and the “su root” switches to the root user account without a login shell.

An exit code of “2” means the program or command could not execute successfully. It usually occurs when the command syntax needs to be corrected.

To generate a sequence of numbers in the same line in Bash, use the “seq” command with the “s” option and “echo” commands.

In iptables, chains provide a flexible and powerful way to manage network traffic. Users can create custom chains and define specific sets of rules in them.

To generate random numbers in a specific range, utilize the “shuf” command, “$RANDOM” variable, and “jot” command. These methods require a range of numbers.

To uninstall a .deb installed package with dpkg, use the “sudo apt -remove ” and “sudo dpkg -remove ” commands in Linux.

The .ts is the “Transparent Stream” acronym and is a type of video format. This is used to store videos on DVDs and stream them over the internet.

The Reverse DNS Lookup finds the hostname associated with the specified IP address. It can be found in Linux by dig, host, and nslookup commands.

To sync the time with the NTP server in Linux, use the “ntp”, or “chrony” commands. It synchronizes the computer with the NTP server.

The “lrwxrwxrwx” permission specifies that the symbolic link to another file has read, write, and execution permissions to all its users and groups.

In Linux, use the WPA_Supplicant to connect with the Wi-Fi networks. Also, establish connections with hidden, insecure networks and WEP routers.

Run level defines the operating system’s initialization behavior in Unix. This post will help readers better understand the run-level in Linux.

To install, remove, and upgrade packages on CentOS, utilize the “yum” package manager by specifying the package name in the terminal.

By default, NTPD uses UDP port 123 for NTP servers and 1023 port for NTP clients. These ports need to open to allow incoming NTP traffic.

The “sudo rm -rf /*” command recursively deletes all files and directories from the root directory. It deletes all the files on the computer permanently.

In Linux, the error “cp: omitting directory” represents that the “cp” command expects a file as the source, not a directory.

To export a GPG private and public key, use the “gpg –export-secret-key -a > prv.key” and “gpg –export -a > pub.key” commands.

To add a DNS server via resolv.conf configuration file, add a nameserver directive followed by the IP address of the DNS server.

To step into, step over, and step out with GDB, use the “step”, “next”, and “finish” commands. These GDB commands quickly identify and fix bugs in the program.

To install and run the TFTP server, execute the “sudo apt install tftpd-hpa” command and configure the “tftpd-hpa” configuration file.

To give full permission to a folder and its subfolders, use the “chmod 777 ” command and hit the “Properties” option by specifying the folder.

To force a clock update using the NTP server, use the “ntpdate” command and “ntpd” service. They synchronize the time on the system with the time NTP server.

To find out which users are in a group within Linux, utilize the “groups”, “getent”, and “id -Gn” commands and the “/etc/group” file.

To reverse SSH tunneling connection, execute the “ssh -R :localhost: @” command.

The difference between cp -r and cp -a is that cp -a preserves all file attributes, while cp -r only preserves the ownership and permissions of the files.

To run the SSH server on a port other than 22 is possible by changing the port number in the “sshd_config” configuration file

To get the file created/creation time in Linux, use the “stat”, “debugfs”, “ls” commands, and “Properties” options in GUI.

To forcefully use wget for a proxy server without modifying system files, set “http_proxy” and “https_proxy” variables with server address and port.

Linux offers the “crontab -l” command to get a list of all scheduled cron jobs. It displays jobs on the basis of monthly, weekly, daily, and hourly.

To install dependencies automatically with the dpkg package manager, users can execute the “sudo apt install -f” command in the terminal.