More and more operating systems become bloated with lots of services that run in the background. While they may not use much CPU time, they increase boot time and RAM usage.
Some Linux distributions include “everything but the kitchen sink,” in an effort to make user life easier. This makes things such as file sharing or printing work out of the box. Unfortunately, the only way to do this is to include hundreds of utilities so that everyone finds something they need.
Fortunately though, open-source operating systems give you the power and freedom to do as you see fit. This means you can disable or remove anything you don’t need. The first option, how to disable services, will be explored here. When you disable, rather then remove, components, there’s less risk of permanently breaking things. And you can go back to the way it was before by simply re-enabling a service if you notice something useful stopped working.
Analyze the Time It Takes for Each Service to Load
Most Linux-based operating systems have migrated to Systemd. Among the suite of utilities it includes, there is a program that lets you analyze how fast your system boots. Specifically, it shows you the total time required to boot and the time it takes for each service to load. Note that some services load in parallel. So, if one requires two seconds to load and the other three seconds, it doesn’t necessarily mean five seconds are required in total. It may be much less than that.
Open a terminal emulator and enter this command:
systemd-analyze
This shows how long it takes for the Linux kernel and base system services to load, which means it doesn’t account for the time your graphical interface requires to boot up. To put it another way, this shows you how much time is required, from the moment the kernel is loaded until you are dropped to the Linux console, which looks like what is depicted below.
If you didn’t have a graphical interface installed, this is what you would be greeted with on your screen.
However, you can also see the time required by the graphical interface to initialize with this command:
systemd-analyze critical-chain graphical.target
This shows that the graphical user interface loaded in 2.126 seconds. This doesn’t account for the time required to load desktop utilities. To enable/disable those, launch your desktop environment startup manager.
Finally, probably the most useful command for the purpose of this tutorial is:
systemd-analyze blame
You can navigate the list with your arrow keys or PAGE UP and PAGE DOWN. Press q to quit.
Use systemctl to Disable Unnecessary Services
As you can see in the previous picture, the snapd service takes 1.295 seconds to load. On an SSD, this is negligible. But on a hard disk, these kinds of times would be in the orders of multiple seconds, and they would add up to a lot in the end. Also, on an SSD many things load in parallel with incredible efficiency. On a hard disk it’s very hard for services to load in parallel. The read heads that float on the disk platters have to move from sector to sector, so it’s almost impossible to truly read data in parallel.
To simplify, imagine this: if on an SSD you would see five services that require one second to boot, it’s likely that the total time required to load all of these might be less than 1.2 seconds. If, on a hard disk, you see the same five services initialize in one second, it’s likely that the total load time is way above five seconds.
Say you don’t need the snapd service, which provides access to containerized application snaps. You can disable it with this command:
sudo systemctl disable snapd.serviceBut, if you reboot, you will notice the snap daemon is still running. That’s because other dependencies may launch it, even if it’s disabled. Try to see what those may be:
systemd-analyze blame | grep snap
snapd.seeded.service and snapd.socket are the culprits here. A child service can request to launch its parent service. When you disable one, you just tell it to not automatically start at boot by itself. But there is a brute-force method to get around this issue.
Use systemctl to Mask a Service
sudo systemctl mask snapd.serviceThis basically makes the service file null so that applications have no way to start the service.
In most cases it’s not this complicated to disable a service. This example has been chosen to show you how to deal with trickier scenarios. In this case, snapd.seeded.service and snapd.socket should be disabled or masked, too.
The following shows the improved boot time.
Conclusion
From 4.078, boot time was reduced to 3.452 seconds, which amounts to a decrease of ~15%. Not too bad, considering just one service was disabled, and this is on an SSD. On a hard disk it’s much easier to get much more significant results.
In this particular example, more services could have been disabled with a command like: sudo systemctl mask avahi-daemon.service ModemManager.service thermald.service pppd-dns.service.
If you prefer a graphical application to manage your services, you can take a look at the Systemd Manager project. You will be limited in what you can do with it, though, since the command line offers much more flexibility.
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