Linux

In a Linux system, everything is logged in a log file under the directory called /var/log. This directory contains logs related to different services and applications. In this directory we have some files such as utmp, wtmp and btmp. Unlike the system log files and the authentication log files, all of these files are binary files. So, we can't use our normal text tools, such as less or grep, to read them or extract information from them. Instead, we'll use some special tools that can read these … [Read more...] about What is the purpose of utmp, wtmp and btmp files in Linux

Changing the UID and GID of a user might seem a trivial task to most of the system admins. But it's not so trivial and it involves a lot more changes in the backend. In this post, we have outlined the exact steps to change the UID and GID of a user "user01". Username: user01 Group: group01 Existing UID: 800 Existing GID: 700 New UID: 900 New GID: 600 Pre-requisites 1. Make sure the user for which UID and GID is to be changed is currently not having any active process running in the … [Read more...] about How to (Correctly) Change the UID and GID of a user/group in Linux

The Problem When we are trying to copy a directory to other location, we get below error: $ cp /data01 /data02 cp: omitting directory '/data01' $ The Solution The error above is a common mistake done by Linux newbies while copying a directory to other locations without using the recursive copy option in the 'cp' command. In order to avoid this error use the "-r" or the "-a" option in the copy command. From the man page of 'cp' command: # man cp -R, -r, --recursive copy … [Read more...] about cp: omitting directory – error while copying a directory in Linux

Files can also have attributes that are expressed in another way than the permissions we have seen so far. An example of this is making a file immutable (a fancy word, which means it cannot be changed). An immutable file still has normal ownership and group and RWX permissions, but it will not allow the user to change it, even if it contains the writable permission. Another characteristic of this is that the file cannot be renamed. In this post, we are going to discuss on how to use chattr … [Read more...] about chattr Command Examples to Change File Attributes (Make files immutable)