Find services that require a restart
Ubuntu offers a live patching utility that allows kernel patches to be installed without requiring a system restart to be applied. Read more about online patching in this post about patching. That said, in many cases other services or processes on your system may need to be restarted after an upgrade.
Finding services that need to be restarted in Ubuntu
sudo apt update
sudo apt install debian-goodies
Now just run
This command will output a list of processes and services that need to be restarted.
Update - 12/26/2016
I just discovered that there is another Debian/Ubuntu program that will not only check for services that need a restart but also restart them for you.
sudo apt install needrestart
Running this program without options will attempt to restart all services that have been updated.
You can also run this program interactively if you want to see which services need to be restarted and choose only the one's that you want to install.
sudo needrestart -r i
Finding services that need to be restarted in Centos 7 and RHEL 7
In Centos 7 and RHEL 7 the utility you need to check this should be installed by default. If not you can install the “yum-utils” package.
sudo yum -y install yum-utils
The command you will want to use is “needs-restarting” and will have to be run as root.
This will again provide a list of services that need to be restarted.
When I originally posted this I neglected to mention OpenSUSE. Suse based distributions use a package manager called zypper, which as a side note is by far my favorite package manager. Anyway zypper natively has the ability to find services and processes that need to be restarted.
sudo zypper ps
Actually since Suse Enterprise Linux is one of my favorite flavors of Linux (I use it at least as much as Ubuntu if not more) I might do a blog early next week focused on package management with zypper.
Restart services manually
In all of the above cases if you are using a modern version of the distribution then you can restart services using systemctl
sudo systemctl restart <service>
If you are using an older version then you will need to run the service command.
sudo service <service> restart