PSMON User Guide
Process Monitor
AED includes a process monitor to ensure that services configured to run by the chkconfig or systemctl systems continue to run. If a service dies, AED will automatically restart the process.
Adding Services to Monitor
To add a service, simply enable it via chkconfig or systemctl and then generate the AED policy for the systems current start. The following steps accomplish this task:
Step 1: Enable a Service
As the root user, run the following command:
systemctl enable <service_name>Example:
systemctl enable httpdStep 2: Generate the AED Policy
Run the following command:
asl -s -f
Removing Services to Monitor
To remove a service, simply disable it via chkconfig or systemctl and then generate the AED policy for the systems current start. Please follow the following steps to do this:
Step 1: Disable a Service
As the root user, run the following command:
systemctl disable <service_name>Example:
service disable httpdStep 2: Generate the AED Policy
Run the following command:
asl -s -f
Disabling PSMON
Note
It is NOT recommended that you disable the process monitor. Doing so will also tell AED to not monitor its own services, and if a service fails for any reason AED will not restart the service.
Please follow the steps below to disable PSMON.
Step 1: Edit the AED Configuration File
Inside of /etc/asl/config set the following:
PSMON_ENABLE="no"Step 2: Update the AED Security Policy
Run the following command:
asl -s -failsStep 3: Kill the PSMON Process(es)
Run the following command:
killall -9 psmonStep 4: Remove the Package
Run the following command:
rpm -e psmon --nodeps
Monitoring Processes with Systemd
Centos/Redhat 7 systems use systemd, which has its own process monitoring capability, psmon is only used to monitor processes that do not use systemd.
To monitor and automatically restart a process, please follow the process below:
Step 1: Check to make sure the service is manged by systemd
Each service will have a service file in /etc/systemd/system directory. For the purpose of this example the multi-user run level will be used, which is the most common run level Linux servers will start in. If you do not know what this means, your system is probably pre-configured to boot into the multi-user run level.
Make sure the service has a functional systemd init script located at:
/etc/systemd/system/mult-user.target.wants/service.serviceStep 2 (Optional): Enable the Service
If the service is not already enabled, enable the service by running the following command:
sudo systemctl enable service.serviceThis will create a symlink in /etc/systemd/system/mult-user.wants/ that looks like the following:
lrwxrwxrwx 1 root root 38 Jan 13 11:54 /etc/systemd/system/multi-user.target.wants/service.service -> /usr/lib/systemd/system/service.serviceThis will enable automatic starting after a reboot.
Step 3: Configure the Service to Automatically Restart
Edit the /etc/systemd/system/mult-user.wants/service.service file. It should contain a line like the example below.
Restart=alwaysIf this is not set to “always”, set it to always and the service will be automatically restarted if it crashes.
Step 4: Reload the Systemd Daemon
Reload the systemd daemon by runing the following command:
sudo systemctl daemon-reloadStep 5: Restart the Service
Restart the service by running the following command:
sudo systemctl restart service.serviceStep 6 (Optional but recommended): Test to see if the service is started on reboot
Run the follwing command to reboot the system:
sudo rebootStep 7: Kill the Process to see if it Automatically Restarts
Run the following command:
killall -9 service
Note
Replace ‘service’ with the service name you want to test, for example httpd.