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22.4. Configuration Examples
22.4.1. Rsync as a daemon Copiar o linkLink copiado para a área de transferência!
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When using Red Hat Enterprise Linux, rsync can be used as a daemon so that multiple clients can directly communicate with it as a central server, in order to house centralized files and keep them synchronized. The following example will demonstrate running rsync as a daemon over a network socket in the correct domain, and how SELinux expects this daemon to be running on a pre-defined (in SELinux policy) TCP port. This example will then show how to modify SELinux policy to allow the
rsync
daemon to run normally on a non-standard port.
This example will be performed on a single system to demonstrate SELinux policy and its control over local daemons and processes. Note that this is an example only and demonstrates how SELinux can affect rsync. Comprehensive documentation of rsync is beyond the scope of this document. See the official rsync documentation for further details. This example assumes that the rsync, setroubleshoot-server and audit packages are installed, that the SELinux targeted policy is used and that SELinux is running in enforcing mode.
Procedure 22.1. Getting rsync to launch as rsync_t
- Run the
getenforce
command to confirm SELinux is running in enforcing mode:getenforce
~]$ getenforce Enforcing
Copy to Clipboard Copied! Toggle word wrap Toggle overflow The command returnsEnforcing
when SELinux is running in enforcing mode. - Run the
which
command to confirm that the rsync binary is in the system path:which rsync
~]$ which rsync /usr/bin/rsync
Copy to Clipboard Copied! Toggle word wrap Toggle overflow - When running rsync as a daemon, a configuration file should be used and saved as
/etc/rsyncd.conf
. Note that the following configuration file used in this example is very simple and is not indicative of all the possible options that are available, rather it is just enough to demonstrate thersync
daemon:Copy to Clipboard Copied! Toggle word wrap Toggle overflow - Now that a simple configuration file exists for rsync to operate in daemon mode, you can start it by running the following command:
systemctl start rsyncd.service
~]# systemctl start rsyncd.service
Copy to Clipboard Copied! Toggle word wrap Toggle overflow Ensure thatrsyncd
was successfully started (the output is supposed to look similar to the one below, only the time stamp will differ):Copy to Clipboard Copied! Toggle word wrap Toggle overflow SELinux can now enforce its protection mechanisms over thersync
daemon as it is now running in thersync_t
domain:ps -eZ | grep rsync
~]$ ps -eZ | grep rsync system_u:system_r:rsync_t:s0 3220 ? 00:00:00 rsync
Copy to Clipboard Copied! Toggle word wrap Toggle overflow
This example demonstrated how to get
rsyncd
running in the rsync_t
domain. Rsync can also be run as a socket-activated service. In that case, the rsyncd
is not executed until a client tries to connect to the service. To enable rsyncd
to run as a socket-activated service, follow the steps above. To start rsyncd
as a socket-activated service, enter the following command as root:
systemctl start rsyncd.socket
~]# systemctl start rsyncd.socket
The next example shows how to get this daemon successfully running on a non-default port. TCP port 10000 is used in the next example.
Procedure 22.2. Running the rsync daemon on a non-default port
- Modify the
/etc/rsyncd.conf
file and add theport = 10000
line at the top of the file in the global configuration area (that is, before any file areas are defined). The new configuration file will look like:Copy to Clipboard Copied! Toggle word wrap Toggle overflow - After launching the
rsync
daemon with this new setting, a denial message similar to the following is logged by SELinux:Jul 22 10:46:59 localhost setroubleshoot: SELinux is preventing the rsync (rsync_t) from binding to port 10000. For complete SELinux messages, run sealert -l c371ab34-639e-45ae-9e42-18855b5c2de8
Jul 22 10:46:59 localhost setroubleshoot: SELinux is preventing the rsync (rsync_t) from binding to port 10000. For complete SELinux messages, run sealert -l c371ab34-639e-45ae-9e42-18855b5c2de8
Copy to Clipboard Copied! Toggle word wrap Toggle overflow - Use the
semanage
utility to add TCP port 10000 to the SELinux policy inrsync_port_t
:semanage port -a -t rsync_port_t -p tcp 10000
~]# semanage port -a -t rsync_port_t -p tcp 10000
Copy to Clipboard Copied! Toggle word wrap Toggle overflow - Now that TCP port 10000 has been added to the SELinux policy for
rsync_port_t
,rsyncd
will start and operate normally on this port:systemctl start rsyncd.service
~]# systemctl start rsyncd.service
Copy to Clipboard Copied! Toggle word wrap Toggle overflow netstat -lnp | grep 10000
~]# netstat -lnp | grep 10000 tcp 0 0 0.0.0.0:10000 0.0.0.0:* LISTEN 9910/rsync
Copy to Clipboard Copied! Toggle word wrap Toggle overflow
SELinux has had its policy modified and is now permitting
rsyncd
to operate on TCP port 10000.