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I'm trying to understand the following in Linux. In windows we have the services that run or "startup". When we install an application it could be installed as a service so that it starts automatically.

But if an application is not installed as a service we usually can see it in the Start -> Programs menu. So we know what applications are installed.

In Linux what is the equivalent? I understand that the equivalent services are in /etc/init where the services start/stop. But I assume that if I install a package it does not necessarily create a startup script in /etc/init right?

So how does one know what has been installed and is available in Linux (like we can in Windows from Start -> Programs)?

Note: I'm asking about CLI mode. I guess in a desktop version one can see the relevant icons in the various menus (e.g in Kubuntu from Application -> Internet -> Firefox).

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  • You can use the package manager to list all installed packages (that the package manager knows about). The details depend on the manager. For Debian-based systems, dpkg -l. For rpm-based systems something like rpm -ql. Feb 4, 2014 at 23:23
  • You find this out through the package manager. Different distributions use different package managers. Are you using (K)Ubuntu? Feb 4, 2014 at 23:54

5 Answers 5

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Many questions. Let's take a couple and see if we can't clear things up.

Q1

I understand that the equivalent services are in /etc/init where the services start/stop. But I assume that if I install a package it does not necessarily create a startup script in /etc/init right?

No when you install applications on Linux distros (ones that make use of package managers such as dpkg/APT, RPM/YUM, pacman, etc.), as part of the software being installed the package manager has a scripting "feature" similar to those found in Windows that can add scripts, create scripts, add users to the system, and start services after they're installed.

Q2

So how does one know what has been installed and is available in Linux (like we can in Windows from Start -> Programs)?

Easy. The same package managers that I mentioned above have commands you can use to query the system to find out what applications have been installed, what files are related to these packages etc. etc.

Example

On Red Hat based distros you can use the command rpm to find out information about the packages installed.

$ rpm -aq | head -5
libgssglue-0.4-2.fc19.x86_64
pygame-1.9.1-13.fc19.x86_64
perl-HTML-Parser-3.71-1.fc19.x86_64
ibus-libs-1.5.4-2.fc19.x86_64
libnl-1.1-17.fc19.x86_64

To find out what files are part of a package:

$ rpm -ql pygame | head -5
/usr/lib64/python2.7/site-packages/pygame
/usr/lib64/python2.7/site-packages/pygame-1.9.1release-py2.7.egg-info
/usr/lib64/python2.7/site-packages/pygame/LGPL
/usr/lib64/python2.7/site-packages/pygame/__init__.py
/usr/lib64/python2.7/site-packages/pygame/__init__.pyc

How can it show me just the executable pieces to that are included in the package (the applications)? Most of the time executables are installed in certain locations on Linux, /usr/bin or /bin are 2 such directories. I usually search the RPM packages like so for these:

$ rpm -ql pygtk2 | grep "/bin"
/usr/bin/pygtk-demo

$ rpm -ql httpd | grep -E "bin/|sbin/" | head -10
/usr/sbin/apachectl
/usr/sbin/fcgistarter
/usr/sbin/htcacheclean
/usr/sbin/httpd
/usr/sbin/rotatelogs
/usr/sbin/suexec
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If you look in /var/log there should be a log of your package manager. For example, arch linux has a log file for pacman and all of the installed, removed, and upgraded programs are listed with a timestamp. This log is a text file.

The specific programs in unix based OSes are saved in /bin, /sbin, /usr/bin, and /usr/sbin; however, they can be saved in a variety of locations.

See this thread for some other locations programs are saved in a unix filesystem. https://askubuntu.com/questions/27213/what-is-the-equivalent-to-the-windows-program-files-folder-where-do-things-g

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I do not think there is any CLI equivalent to GUI to discover programs the way they jump at you. It is more exploratory. When I get on to a new linux system, I look at the /opt directory to find what all optional packages are installed other than the standard utilities. If I am looking for a specific utility, I use apropos, locate, which and/or whereis.

If admins have already installed certain utilities then I would expect them in my env and system path so I look into these. Additionally, I also look into system-wide aliases if any.

Some large scale systems have modules and/or softenv installed. In such cases, I look into module avail or softenv. On systems with package managers like apt or yum, you can use them to list installed packages: yum list installed and with rpm: rpm -q myfavtool.

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  • /opt is quite specific; different systems have different conventions. Other places to explore are /usr/local and /srv, or more generally any nonstandard directory directly under the root directory.
    – tripleee
    Jan 6, 2023 at 6:52
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You can run

cat /var/log/dpkg.log | grep -i <search_text> to see if your desired package name <search_text> is already installed.

Works for me in Ubuntu.

Regards,

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  • You don't read the log for that, dpkg -l package tells you the status of a package and you can use a wildcard like dpkg -l 'docker*' if you don't know the exact name. The output shows packages you have not installed, too, so you can learn about interesting packages related to a keyword.
    – tripleee
    Jan 6, 2023 at 6:50
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I know this is nearly 9 years old but in case this helps someone...

In windows we have the services that run or "startup".

It is not that simple. In Windows services can be set to start automatically but they can be set to either Manual or Disabled.

Back in the days of DOS there were device drivers that were designed based on Unix (consider Unix here to be the same as Linux but that is an over-simplification) device drivers. In Windows Microsoft renamed them Services. Not all Services are device drivers. All device drivers in Windows are Services.

When we install an application it could be installed as a service so that it starts automatically.

No. Windows Services cannot have a GUI. There were previous versions of Windows that did allow Windows Services to have a GUI but Microsoft has removed that. A Windows Service is different from a Windows application. It might be possible to install a Windows console application without a console as a service but not most Windows applications.

in the Start -> Programs menu

That menu is just a folder with shortcuts and subfolders with shortcuts. Shortcuts can exist in other places or even nowhere (seen by the user) without being in the Start -> Programs menu. In Windows applications can be put somewhere, most anywhere, and if the location of it is in the Path environment then the application can be executed the same as it was installed in some other way, except Windows Applications require more to be done by a setup program.

In Windows applications can execute without a window and then they do not appear as a "Process" in the Task Manager.

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