Checklist for Running Networking Services (Fedora)

2009-12-20 13:34| 发布者: admin| 查看: 55| 评论: 0|原作者: 段誉

Checklist for
Running Networking Services
As computer security issues increase with the rising
onslaught of computer crackers and viruses, operating systems (such as Fedora or
RHEL) in regards to the services they provide are moving toward more security
rather than more ease-of-use. Simply installing server software isn't enough to
get the service up and running.
If a service isn't working, check the following items to hunt down
the problem:
Is the software package installed? Each network service is
represented by one or more software packages. Use the command rpm -qc packagename to find
configuration files, and the command rpm -qd packagename to find documentation. If you selected
only packages associated with Desktop categories when you first installed
Fedora, most network server software may not be installed on your computer at
all. Check

for information on how to
change your firewall configuration to open ports that provide the different
services.
Is the start-up script set up to launch the service
automatically? Most network services are launched from start-up scripts that
cause daemon processes to listen to the network continuously for requests for
the service. See the "
find start-up scripts and have them launch automatically.
Does SELinux permit access to the service? When SELinux is
enabled, it puts an additional layer of security over selected network services.
If you get permission denied messages when you are sure
that the firewall and file/directory permissions are set appropriately, run
system-config-securitylevel. On the SELinux tab, check
that the appropriate service (Web, FTP, Samba, and so on) is enabled. You can
also disable SELinux to see if that solves the problem or simply set it to
Permissive mode (to only have SELinux display messages about security issues,
without enforcing them).
Is the configuration file created for the service? Even if
the daemon process is listening for requests for a network service, one or more
configuration files associated with the service must probably be set up before
requests will be accepted.

Debugging Services
Nearly every service also has an option for running in
different debug levels. By turning on debugging, you can see everything from
failure messages to detailed information on everything the service does.
Usually, you can either add a debug option to an init script (often passed by
options set in /etc/sysconfig files) or run a daemon process manually from the
shell with debug options added. For example:
# /usr/sbin/sshd -ddd -f /etc/ssh/sshd_config -p
52222

This example starts the secure shell daemon (sshd) in maximum
debug mode (-ddd). It uses the sshd_config for its configuration and listens for
connections on port number 52222. This port is just begin used for testing
purposes, so not to conflict with any common ports. Watch the debug messages
appear in the Terminal window. Next you could have an ssh client from another
computer try to connect to this server:
$ ssh -l testuser 192.168.1.246 -p 52222

Assuming here that the server's IP address is 192.168.1.246,
this example attempts to connect to the sshd server run earlier on port 52222.
It tries to log in as the user named testuser. By watching sshd debug messages,
you can check that the client can communicate with the server and that the
configuration file is working properly.

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The rest of this appendix provides an overview of the daemon
processes, start-up scripts, configuration files, and software packages that are
associated with the networking services that come with Fedora and
RHEL.

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Checklist for Running Networking Services (Fedora)

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