The UNIX shell program interprets user commands which are either directly entered by the user, or which can be read from a file called the shell script or shell program. Shell scripts are interpreted, not compiled. The shell reads commands from the script line per line and searches for those commands on the system.
The below command is used to check known shells in a UNIX system.
root@localhost$ cat /etc/shells
# List of acceptable shells for chpass(1).
# Ftpd will not allow users to connect who are not using
# one of these shells.
/bin/bash
/bin/csh
/bin/dash
/bin/ksh
/bin/sh
/bin/tcsh
/bin/zsh
To change the shell, just write down the shell name; since a shell is an executable file (program), the current shell activates it and it gets executed. A new prompt is usually shown because each shell has its typical appearance.
Tired of filtering semi-structured data from command output? What if I tell you can easily filter from structured or unstructured document data. Yes, you heard it right, we are talking about JSON [JavaScript Object Notation]. JSON is a text-based data format programming language that is used to serialize and transmitting structured or unstructured data or we can say semi-structured data over a network connection.
But Why Json ?
We generally think JSON means data provided general output from any API. But, if we talk about any technology, JSON is a very common programming language or we can say format, which is used as the output format of any resource. While using DevOps tools like Docker, Ansible, or any other tool, we generally get the output in JSON format when we use any output command like Docker inspect or Ansible facts gather.
This error may strike your Ubuntu at any point at the moment. A few days ago when I was doing my routine work in my Ubuntu laptop, suddenly I encountered with an error “Segmentation fault ( core dumped)” then I got to know that, this error can strike you Ubuntu or any other operating system at any point of the moment as binaries crashing doesn’t depend on us.
Segmentation fault is when your system tries to access a page of memory that doesn’t exist. Core dumped means when a part of code tries to perform read and write operation on a read-only or free location. Segfaults are generally associated with the file named core and It generally happens during up-gradation.
While running some commands during the core-dump situation you may encounter with “Unable to open lock file” this is because the system is trying to capture a bit block which is not existing, This is due to the crashing of binaries of some specific programs.
You may do backtracking or debugging to resolve it but the solution is to repair the broken packages and we can do it by performing the below-mentioned steps:
Command-line:
Step 1: Remove the lock files present at different locations.
sudo rm -rf /var/lib/apt/lists/lock /var/cache/apt/archives/lock /var/lib/dpkg/lock and restart your system h.cdccdc
Step 2: Remove repository cache.
sudo apt-get clean all
Step 3: Update and upgrade your repository cache.
sudo apt-get update && sudo apt-get upgrade
Step 4: Now upgrade your distribution, it will update your packages.
sudo apt-get dist-upgrade
Step 5: Find the broken packages and delete them forcefully.
sudo dpkg -l | grep ^..r | apt-get purge
Apart from the command line, the best way which will always work is:
Step 1: Run Ubuntu in startup mode by pressing the Esc key after the restart.
Step 2: Select Advanced options for Ubuntu
Step 3: Run Ubuntu in the recovery mode and you will be listed with many options.
Step 4: First select “Repair broken packages”
Step 5: Then select “Resume normal boot”
So, we have two methods of resolving segmentation fault: CLI and the GUI. Sometimes, it may also happen that the “apt” command is not working because of segfault, so our CLI method will not work, in that case also don’t worry as the GUI method gonna work for us always.
