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find the oldest file in the directory find  .  -type f -printf '%T+ %pn' | sort | head -n 1 ...

Run following command first to see exactly which files you will remove.  find . -name "*.bak" -type f Also, make sure that -delete is the last argument in your command. If you put it before the -name *.bak argument, it will delete everything.  But use it with precaution.  find . -name "*.bak" -type f -delete ...

Let's encrypt SSL certificates will get expired after 90 Days of installation and you must renew it before it get expired. Certbot Renew Command $ sudo certbot renew --dry-run Certbot Auto Renew Cron Job $ cat /etc/cron.d/certbot Content: # /etc/cron.d/certbot: crontab entries for the certbot package # # Upstream recommends attempting renewal twice a day # # Eventually, this will be an opportunity to validate certificates # haven't been revoked, etc....

Note: you should stop apache before upgrade. You should back up your conf files, such as apache2.conf, php.ini, my.ini, and all VirtualHost settings. Run simple command to upgrade.  sudo do-release-upgrade After server restarted, login and STOP apache2 to prevent PHP short end breaks php rendering. Enable new php short hand tag in php.ini if it is needed for your code. sudo apt-get remove php7.2-common sudo apt...

check current version: lsb_release -a Install Available Updates apt-get update apt-get upgrade apt-get dist-upgrade Stop Services service apache2 stop START UPGRADE 1. Install the update-manager-core package: apt-get install update-manager-core 2. Open /etc/update-manager/release-upgrades and verify that the Prompt value is set to lts: Prompt=lts 3. You’re now ready to begin the upgrade to Ubuntu 16.04 LTS: do-release-upgrade Follow the on-screen instructions to complete the installation process. Install and Update php7.0 properly after upgrade. note: you might want...

du -sch .[!.]* * |sort -h ...

You need to set up a DNS server. (install dnsmasq (is light) or bind (is rather heavy)). To install... Ubuntu OS: sudo apt-get install dnsmasq In /etc/NetworkManager/dnsmasq.d/dnsmasq-localhost.conf and address=/localhost.com/127.0.0.1 restart sudo /etc/init.d/dnsmasq restart with Mac OS: Install dnsmasq brew update # Always update Homebrew and the formulae first brew install dnsmasq sudo brew services start dnsmasq sudo brew services start dnsmasq Configure dnsmasq Its default configuration file is located at /usr/local/etc/dnsmasq.conf and contains examples of...

Command line: File permissions The commands for modifying file permissions and ownership are: chmod – change permissions chown – change ownership. chmod – the command to modify permissions R – this modifies the permission of the parent folder and the child objects within ugo+rw – this gives User, Group, and Other read and write access. The breakdown of permissions looks like this: u – user g – group o –...

How to See Which Groups Your Linux User Account Belongs To? groups How to add a new group?  sudo groupadd How to add user to a group? usermod -a -G   Change a User’s Primary Group While a user account can be part of multiple groups, one of the groups is always the “primary group” and the others are “secondary groups”. The user’s login...