Archives for April 2018

The shutdown command is the preferred method of rebooting or shutting down Linux. Using shutdown you can schedule a reboot or shutdown at some time in the future, and shutdown will automatically notify all logged-in users of the impending action. As the time approaches, it will alert logged-in users with a greater frequency and urgency. […]

The rc script When init enters a runlevel, it calls the rc script with a numeric argument specifying the runlevel to go to. rc then starts and stops services on the system as necessary to bring the system to that runlevel. Though typically called at boot, the rc script can be called by init to […]

The strace Command The strace command can be used to intercept and record the system calls made, and the signals received by a process. This allows examination of the boundary layer between the user and kernel space which can be very useful for identifying why a process is failing. Using strace to analyze how a […]

As the name implies, a chroot operation changes the apparent root directory for a running process and its children. It allows you to run a program (process) with a root directory other than /. The program cannot see or access files outside the designated directory tree. For example, you can run a program and specify […]

Use the ssh-keygen command to generate a public/private authentication key pair. Authentication keys allow a user to connect to a remote system without supplying a password. Keys must be generated for each user separately. If you generate key pairs as the root user, only the root can use the keys. The following example creates the […]

The ssh-agent program is an authentication agent that handles passwords for SSH private keys. Use ssh-add to add the keys to the list maintained by ssh-agent. After you add a private key password to ssh-agent, you do not need to enter it each time you connect to a remote host with your public key. Generating […]

Checksum programs are used to generate checksum key strings from the files and verify the integrity of the files later by using that checksum string. A file might be distributed over the network or any storage media to different destinations. Due to many reasons, there are chances of the file being corrupted due to a […]

There are several possibilities to check and validate PHP version on Linux. 1. Open a bash shell terminal and use the command “php –version” or “php -v” to get the version of PHP installed on the system. # php –version PHP 5.4.16 (cli) (built: Mar 7 2018 13:34:47) Copyright (c) 1997-2013 The PHP Group Zend […]