Tips

Here are some quick notes on how I installed letsencrypt certificates on a couple of my old Fedora servers. This is meant to get you started fairly quickly especially if you know how to install web servers on Linux systems. While there is a client already available for Fedora 23, I found that on older versions, the apache plugin for letsencrypt does not work. For instance, when you run the command:

./letsencrypt-auto --apache -d mydomainname.com, you get an error like:

The apache plugin is not working; there may be problems with your existing configuration.
The error was: NoInstallationError()

For earlier versions, you need to install the manual way i.e. generate a certificate. While that’s a few steps from the easy and automated promise of lets encrypt, you still can’t beat the price tag of Free!

Pull the sources for letsencrypt:

git clone https://github.com/letsencrypt/letsencrypt


Change to directory:

cd letsencrypt

Run the following command, and ofcourse replace the string mydomain.com with your domain:

./letsencrypt-auto certonly --standalone --agree-tos --email joe@mydomain.com -d mydomain.com

NOTE: For multiple domains, just add ‘-d mydomain.net’
Get help by running:

./letsencrypt-auto --help

If all goes well, you should see a congratulatory message, with the location of your free certificate chain! Use this in apache or nginx configuration

Keep in mind that the certificates are only vailid for three months, and you will need to do this again.

As systemd becomes the default method of handling services in all major Linux distributions, below are some quick and easy-to-remember commands that will make you look like a pro.

systemctl

• check for all running units
  systemctl
  TIP: To show all units, including in-active ones:
  systemctl list-unit-files

• Check for failed units
  systemctl --failed

• Start, stop, restart units
  systemctl start postfix.service
systemctl restart postfix.service
systemctl stop postfix.service

• Check status of a specific unit
  systemctl status mysqld.service
  TIP: Use -l for detailed status

• Enable or disable services
  systemctl enable firewalld.service
systemctl disable NetworkManager.service
TIP: If you disable a service, and it still runs,
  systemctl mask NetworkManager.service
  Use ‘unmask’ to restore it

• See if a specific unit is enabled
  systemctl is-enabled iptables.service

• Create a snapshot – useful for testing various targets
  systemctl snapshot example.snapshot
  TIP: To activate it:
  systemctl isolate example.snapshot


• Reboot/poweroff/suspend your machine
  systemctl reboot
systemctl poweroff
systemctl suspend

• Change current target – i.e. runlevel
  systemctl isolate graphical.target

• To list current target
  systemctl list-units --type=target

systemd

• See which units take a long time to start during boot up
  systemd-analyze blame
  TIP: You can plot the boot up using:
  systemd-analyze plot

• See when a unit started and how long it took
  systemd-analyze critical-chain

journalctl

• Create a running log like ‘tail -f /var/log/messages’
  journalctl -f -o cat --no-pager

• Running log for a specific unit
  journalctl -f -o cat --no-pager -u httpd.service

• See boot messages – like ‘dmesg’
  journalctl -b

Manage remote systems:
systemctl status sshd -H root@1.2.3.4

For detailed instructions on these and more commands, man as always is your best friend.

With most Linux distros now using GNOME 3.10+, here are a few commands on changing the look and feel of your desktop using gsettings. Other CLI methods exist such as the popular GNOME tweak tool and Dconf.

Add apps to favorites bar
$ gsettings set org.gnome.shell favorite-apps "['google-chrome.desktop', 'evolution.desktop', 'nautilus.desktop', 'libreoffice-writer.desktop', 'libreoffice-calc.desktop', 'firefox.desktop', 'gnome-terminal.desktop', 'vlc.desktop', 'jitsi.desktop', 'gedit.desktop', 'gcalctool.desktop']"

Change show date and clock format
$ gsettings set org.gnome.desktop.interface clock-show-date true
gsettings set org.gnome.desktop.interface clock-format '12h'


Change background picture
$ gsettings set org.gnome.desktop.background picture-uri 'file:///usr/share/backgrounds/gnome/Sandstone.jpg'

Those are just but a few of the settings available for you to tweak. To see all of them, type:
$ gsettings list-keys .