nixCraft Linux & Unix Sysadmin/DevOps Tutorial Newsletter

[nixCraft]

Welcome to nixCraft Linux/Unix newsletter for Saturday, 07 December 2019. I hope you will enjoy this version of the newsletter.

• Debian Linux 10.2 released and here is how to upgrade it {trending}
  The Debian GNU/Linux project has released an updated version of its stable Linux distribution Debian 10 (“buster”). You must upgrade to get corrections for security problem as this version made a few adjustments for the severe issue found in Debian version 10.1.
   
• Debian / Ubuntu Linux Delete Old Kernel Images Command
  I'm a new Ubuntu Linux user and noticed that old kernel still exists in my system. Why doesn't Ubuntu remove old kernels automatically? How do I delete old unused kernel images to free disk space. How to remove unused old kernel images on Ubuntu Linux safely?
   
• How to generate RSS 2.0 feed quickly using Python
  I wanted to generate RSS 2.0 feeds in Python. Nothing fancy but for certain tasks I needed it something that is quick and just works out of the box. I found rfeed. It is a library to generate RSS 2.0 feeds in Python. It is in my opinion straightforward to use. This post explains how to generate RSS 2.0 feed quickly using Python.
   
• Linux Change or Rename User Name and UID
  How do I change user name (rename user name) or UID under a Linux operating system using command line tools? How do I change or rename username in Linux?
   
• Bash Assign Output of Shell Command To Variable
  How do I assign the output of a shell command to a shell variable under Unix like operating system? For example, I want to store the date command output to a variable called $now. How do you do that? How can I set a variable to the output of a command in Bash?
   
• Bash check if process is running or not on Linux / Unix {trending}
  I am new to Linux shell scripting. I am using a CentOS 7 Linux and Ubuntu 18.04 LTS server in the cloud. How do I check if a process is running or not on Linux? How do I determine whether a process is running or not in a shell script running on an Ubuntu server?
   
• FreeBSD Find Out All Installed Hard Disk Size Information
  How do I find out all installed hard disk drive names under a FreeBSD operating system without rebooting the server? How do I use the equivalent of fdisk -l in Linux, with FreeBSD to list all hard disks drives? How can I find hard disk size in FreeBSD?
   
• How to delete empty lines using sed command under Linux / UNIX {trending}
  I need to delete all empty lines but could not figure out sed command for the same. How do I delete all empty lines with sed under Linux or Unix-like systems?
   
• Linux prevent unprivileged users from viewing dmesg {trending}
  I want to restrict both normal users and root user inside LXD container “hypervisor” from viewing and using dmesg command output. How do I prevent non-root (unprivileged) Linux users from viewing the Linux kernel’s log buffer? Can Linux prevent unprivileged users from viewing dmesg command output?
   
• RHEL / Centos Linux Disable Firewall Command
  How do I disable firewall on CentOS or Red Hat Enterprise Linux server version 5.x/6.x running on my HP micro server?
   
• Linux hide processes from other users and ps command {trending}
  I run a multi-user system. Most users access resources using SSH client. How can I stop leaking process information to all users on Linux operating systems? How do I prevent users from seeing processes that do not belong to them on a Debian/Ubuntu/RHEL/CentOS Linux server? Is there any way to hide other users process when running ps command?
   
• How to mount an ISO image/file under Linux
  You can mount an ISO file or images via the loop device under Linux. It is possible to specify transfer functions (for encryption/decryption or other purposes) using loop device. This page explains how to mount ISO files on Linux.
   
• Bash Read Comma Separated CSV File on Linux / Unix {trending}
  How do I read comma separated CVS file under UNIX / Linux / BSD / MacOS bash script? How can I parse a CSV file in Bash?
   
• Bash History Display Date And Time For Each Command
  How do I display shell command history with date and time under a Linux, MacOS or Unix-like operating systems? How do I see date and time stamps in bash history command running on a Linux or Unix-like systems?
   
• VI / VIM – Open File And Go To Specific Function or Line Number
  How do I open a text file using VIM or VI and go to specific line? How do I open a file using vim and go to specific function() in my source code?
   
• /proc/filesystems: Find out what filesystems supported by Linux kernel
  So, How do you find out or see which filesystems are supported by the Linux kernel?
   
• How to find a website’s DNS (name server) address
  How can I find a website’s DNS address? How do I check the current DNS servers of a domain or website using a Linux or macOS command line option? How do I find DNS address of a website using bash?
   
• How to find fan speed in Linux for CPU and GPU {trending}
  What commands I need to type to find out fan speed for GPU and CPU in Linux?
   

• bash: file: command not found. How to install file
  I am running file /usr/sbin/arp command on a Debian VM minimal but getting an error that read as:
  bash: file: command not found
  How do I fix this error on a Debian or Ubuntu Linux system? How can I install file command on Linux cloud?

• Bash get filename from given path on Linux or Unix
  How do I extract filename and extension in the Bash shell script from the given path? How can I get filename from the path under the bash shell?
   
• How to return pid of a last command in Linux / Unix
  I need to find and return the PID of the last command executed in Linux. How do I return the PID of command in Linux?