BASH Shell – nixCraft

How to upgrade LXD VMs powered by Ubuntu/Debian or CentOS Linux

July 11, 2017in BASH Shell, CentOS, Debian / Ubuntu, Linux, Linux Containers (LXC) last updated July 11, 2017

I run over 10+ LXD VMs powered by CentOS Linux 7 and Debian/Ubuntu Linux. How do I upgrade all VMs automatically or on demand using Ansible tool?

How to check and verify md5/sha1/sha256 checksums for Apple MacOS X when I download files

June 30, 2017June 30, 2017in BASH Shell, Mac OS X, Security, UNIX last updated June 30, 2017

Malware is becoming more and more common for macOS. I wanted to make sure file I downloaded files such as an ISO image or firmware are safe before install on my system. How do I verify md5 or sha1 or sha256 checksums for my Apple MacOS X when I download files from the Internet?

How to display countdown timer in bash shell script running on Linux/Unix

June 24, 2017June 24, 2017in BASH Shell, Linux, UNIX last updated June 24, 2017

I want to display a countdown before purging cache from CDN network. Is there an existing command to show a conuntdown from 30..1 as 30,29,28,…1 on Linux or Unix bash shell script?

How to find and delete directory recursively on Linux or Unix-like system

June 20, 2017June 22, 2017in BASH Shell, Linux, UNIX last updated June 22, 2017

I type ‘find . -type d -iname foo -delete‘ command to find the foo directories and delete them. However, I am getting an error message that read as find: cannot delete './hourly.4/data/foo': Directory not empty on Linux server. How do delete directories based on find command output on Linux or Unix-like system?

How to run cron job every minute on Linux/Unix

June 18, 2017June 18, 2017in BASH Shell, Commands, Linux, UNIX last updated June 18, 2017

I want to run a cron job that should run a specific shell script /home/jobs/sync.cache.sh every minute. How do I use crontab to execute script every minute on Linux or Unix-like system?

How to prevent sed -i command overwriting my symlinks on Linux or Unix

June 13, 2017June 13, 2017in BASH Shell, CentOS, Debian / Ubuntu, FreeBSD, Linux, Mac OS X, RedHat and Friends, Suse, Troubleshooting, UNIX last updated June 13, 2017

I recently ran a command ‘sed -i 's/CONFIG_1/CONFIG_OPT_2/g' /etc/nginx/sites-enabled/*.conf‘ on a Debian Linux server. However, the sed command destroyed the link and created a regular file in place of the link file. How can I prevent my ‘sed -i’ command from destroying symlinks on Linux or Unix-like system?

How to extract multiple tar ball (*.tar.gz) files in directory on Linux or Unix

May 30, 2017May 30, 2017in BASH Shell, CentOS, Debian / Ubuntu, FreeBSD, Linux, RedHat and Friends, Suse, UNIX last updated May 30, 2017

I have tried tar -xvf *.tar.gz command, but getting an error that read as:
tar (child): *.gz: Cannot open: No such file or directory
tar (child): Error is not recoverable: exiting now
tar: Child returned status 2
tar: Error is not recoverable: exiting now
How can I extract multiple *.tar.gz files in directory using Linux or Unix-shell prompt?