what makes you write community documentation?

[Dan Smith]

Test case services quick rough draft. Shows support for KDE, Gnome and
command line. I have not spell checked this or run it through a grammar
checker or done any proofing of any sort on it. Just a quick example that
took me about 15 minutes to write. The screenshots are meant to be embedded
in the document but will be attachments with this email.


Services/daemons are programs that perform useful functions on your system
but are not normally started by the user. MySQL for example runs normally as
a service. You don't launch MySQL every time you need to connect to the
database it is normally always running once you configure it unless you
manually shut it down.

Services not only start or don't start at boot time. They can be turned on,
off or restarted without restarting the machine. Services can also run only
at certain run levels. Run levels are various states the machine can exist
in. There are only two run levels most Linux users are likely to see. Run
level 5 which is today the default for most systems. That is a fully
graphically enabled environment. The other is run level 3 which is typically
used for trouble shooting and low level system driver installation.


In general it is best to turn off any service you are not using. Leaving a
service you do not use running is taking a chance there will be a
vulnerability in that software which you are not using. For example with
Fedora Bluetooth is enabled by default. If you are not using Bluetooth there
is no reason to keep the service running. Until recently ISDN ran by
default. If you do not use ISDN to connect to the net there isn't any reason
to have it installed much less running. If you are unsure about what a
service does there are several ways to find out. The GUI service menus often
have descriptions. If you from a command line use man service name it will
produce documentation about many services. In general it is best to leave it
running if you are not sure if you'll need the service or what that service
does.

To configure your services
In KDE
click on the Fedora icon in the bottom left corner. You should see
Administration up at the top. If you do not install the KDE admin tools from
either Yum or a yum GUI such as yum extender or kyum.

In Gnome click on System

In both KDE and Gnome
Click on administration select Server settings then select services.

You will be asked for the root password. Then you will see a screen like
this.
(screenshot kdeservices1.png)
By clicking on a service you will get a description of that service and it's
status. Services without a check mark are not started at run time. To
prevent a service from running at start up uncheck the box next to it. To
enable a service at start up check the box.

To stop a service select it then click on the stop button. In this example I
started the denyhosts service.
(screenshot kdeservices2.png)

The on demand services tab is for services that are loaded when a client
program calls them. Amanda for example is a backup system. It only runs when
an Amanda client talks to the system.
(screenshot kdeservices3.png)

To save the new configuration click on the save button. If you do not do
this the services you schedule/unscheduled to start at run time will not be
changed. If you click on the revert button it erases all the changes you
have made.


You can also configure services from the command line using chkconfig.

Open a term window.
su -  to root. Make sure to use the - so that you have root's path and
environment variables set up.

The basic usage of chkconfig is.
To list services
chkconfig --list
This will produce a screen similer to this.
(screenshot chkconfig1.png)

To disable a service use
chkconfig --level 2345 sendmail off
for example to turn sendmail off on run levels 2,3,4 and 5.

To turn sendmail on you'd use for run levels 3 and 5
chkconfig --level 35 sendmail on

To see other chkconfig options use man chkconfig.

To manually turn a service off, restart or turn one on from the command line
use the service command.

As root.
service sendmail restart
would restart the sendmail service.
(screencap cserv1.png)
In the screen capture you see an example of stopping a service that failed.
In this case because the service was already stopped. You will also see an
example of starting NFS. Notice that not just NFS started. 3 other services
started automatically when NFS started. Many services are like this.

There is one final way to edit services. It is highly recomended that you
use the chkconfig or GUI tools to modify services as well as the service
command. To stop a service you can use PS to aquire it's PID and then stop
the PID using the kill command.  To modify what run time level and stop or
start you would have to edit the /etc/rc files.

rc          rc1.d/      rc3.d/      rc5.d/      rc.d/       rc.sysinit
rc0.d/      rc2.d/      rc4.d/      rc6.d/      rc.local

Each dir corresponds with the run time level. So to edit a service for run
time level 5 you would modify the corresponding file in the /etc/rc5.d/ dir.
This is not recommended for any but very experienced users. On rare
occasions you will have to modify these files to change default behavior.
Generally you will never have to directly touch these files.
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