A lot of programs are started by default in each desktop session. Many of them are unnecessary; some of them are annoying or can even cause problems. And some are useful if you want them, but annoying/slow etc when you don't. Users can disable everything they don't need.

To change which programs are active, run the session properties control panel tool for your desktop:

• Gnome: gnome-tweak-tool (not in the application or actions menu any more, nor part of the settings panel, so it has to be run from the commandline!).
• Cinnamon: cinnamon-session-properties, it is in the “System settings” control panel app as “Startup applications”.
• Mate: mate-session-properties

On the tab “Startup programs”, remove the checkmark in front of the command you don't want.

The following services are useless on our desktop systems and can safely be disabled (some already are, in our default install, but it doesn't hurt to make sure!):

• Blueman (Bluetooth, not present on most systems)
• esc (smartcard security utility, not present)
• PackageKit (update notification; not useful to users since we install the updates for you) Also: use gpk-prefs (or the preferences from the notification icon to disable these notifications)
• dnfdragora: (another update tool)
• Network (NetworkManager control tool; very usefull for wireless connections, but useless for desktops with a fixed network connection where the network has a fixed setup which users should never modify)

These services may be disabled if you don't want them, but that is up to you; they can be useful, if configured properly:

• mail-notification (A mail icon in the panel, needs to be configured and it pops up a configuration dialog on every login if you have not configured it yet, so if you don't use it, get rid of it)
• User sharing (a tool that allows users to share a directory with other users)
• User folders update (updater for the “special” directories like Documents, Downloads etc)
• ABRT - automatic bug reporting tool. if a program crashes, this program will attempt to file a bug report. But you will need to register in the fedora bug tracker, and it will be useless for programs from other sources (e.g. IDL or own programs)
• Caribou: on-screen keyboard (nice for tablets, useless in most other cases)
• Disk Notifications - gives a popup if a disk is almost full. No quota warnings, however.
• Evolution alarm notify - useful to get alarms from the calendar in Evolution, but useless if you don't use Evolution or its calendar.
• Tracker - the Gnome 3 search tool. There are 3 services running and since tracker tries to index all files, including those on network disks, it will be slow, and its cache and index (in home) will be large.
  Note: see below.
• Zeitgeist-datahub - Another search/history tool in GNOME and Cinnamon. Can be useful, if used (similar to the search features in Google Now and Apple's Spotlight, including searching recent files, recent apps, web history etc). But if you don't use it, it is a waste of memory.
• Skype - this service adds a quick-start icon for skype, but you can disable it and start skype from the menu, to save some memory and startup time
• Depending on your desktop choices, there may be duplicates in the session, eg: screensavers for Gnome, and for Mate. Disable whatever you don't use to speed things up a bit.

The tracker file indexer will run by default in some cases, even if it doesn't show up in your startup applications. If that is the case, and you want to disable it, run tracker3 reset -r -s to stop the processes and remove all indexes, if you want the service completely disabled. To be even more sure it will not be started automatically, execute this:

touch ~/.config/autostart/tracker-miner-rss-3.desktop ~/.config/autostart/tracker-miner-fs-3.desktop 

(these files in your .config will override the system files, and since you are creating empty files here, nothing will be started)

The reason why you may want to disable these services: even though a desktop search engine sounds like a good idea, but indexing all of the big data disks as soon as you access them, takes a lot of network bandwith, cpu time and memory, and storing the index of the disks will probably exceed your home disk quota.

The Baloo file indexer is another desktop search engine, which can consume huge amounts of memory. To switch it off, run:

balooctl disable

Evolution is a mail/calendar suite, and can be a very useful tool, if you use it. Unfortunately, a lot of programs are started in each user session, even if you don't need them, or even if you have never used evolution. These programs don't show up in the usual session program dialogs, but from the commandline it is possible to disable them:

systemctl --user daemon-reload
systemctl --user disable --now evolution-source-registry
systemctl --user disable --now evolution-calendar-factory
systemctl --user disable --now evolution-addressbook-factory
systemctl --user disable --now evolution-alarm-notify