Installing ClamAV on CentOS 7 and Using Freshclam

Including the usage of Freshclam

To get ClamAV on CentOS installed, we have to use the EPEL repository (Extra Packages for Enterprise Linux). Fortunately, the Fedora project provides this with an easy installation. Unfortunately the default configuration is not properly working. In this post we collect some of the issues and required changes.

Let’s start with installing the EPEL support.

yum install epel-release

Next step is installing all ClamAV components.

yum install clamav-server clamav-data clamav-update clamav-filesystem clamav clamav-scanner-systemd clamav-devel clamav-lib clamav-server-systemd

Configure SELinux for ClamAV

If you are using ClamAV on CentOS, together with SELinux, we should configure it a little bit. This way ClamAV can access all files on disk, and update its data definition files.

Enable antivirus_can_scan_system:

setsebool -P antivirus_can_scan_system 1

During database load : LibClamAV Warning: RWX mapping denied: Can't allocate RWX Memory: Permission denied

Configuration of Clam daemon

Copy a the clamd.conf template, in case you don’t have a configuration file yet.

cp /usr/share/clamav/template/clamd.conf /etc/clamd.d/clamd.conf  
sed -i '/^Example/d' /etc/clamd.d/clamd.conf

Change /etc/clamd.d/clamd.conf file and define if you want to run the scanner as root, or a specific user. Check your /etc/passwd file for the related Clam user.

Change the following two options:

User clamscan
LocalSocket /var/run/clamd./clamd.sock

Enable Freshclam

Freshclam helps with keeping the database of ClamAV up-to-date. First delete the related “Example” line from /etc/freshclam.conf.

cp /etc/freshclam.conf /etc/freshclam.conf.bak  
sed -i '/^Example/d' /etc/freshclam.conf

Check the other options in the file, and change it to your preferred settings.

Missing systemd service file

We didn’t get a systemd service file, so creating a quick file here. The process should be forking itself and start freshclam in daemon mode. In this case we configure it to check 4 times a day for new files.

Create a new file /usr/lib/systemd/system/clam-freshclam.service

# Run the freshclam as daemon
[Unit]
Description = freshclam scanner
After = network.target

[Service]
Type = forking
ExecStart = /usr/bin/freshclam -d -c 4
Restart = on-failure
PrivateTmp = true

[Install]
WantedBy=multi-user.target

Now enable and start the service.

systemctl enable clam-freshclam.service
systemctl start clam-freshclam.service

Check the status.

# systemctl status clam-freshclam.service
clam-freshclam.service - freshclam scanner
Loaded: loaded (/usr/lib/systemd/system/clam-freshclam.service; enabled)
Active: active (running) since Thu 2015-06-11 11:09:24 CEST; 1s ago
Process: 3158 ExecStart=/usr/bin/freshclam -d -c 4 (code=exited, status=0/SUCCESS)
Main PID: 3159 (freshclam)
CGroup: /system.slice/clam-freshclam.service
└─3159 /usr/bin/freshclam -d -c 4

Change service files

By default, the service files seem to be messy and not working.

These are the files bundled:

When enabling the clamd service, we would see something like this:

# systemctl enable /usr/lib/systemd/system/clamd@.service
Failed to issue method call: Unit /usr/lib/systemd/system/clamd@.service does not exist.

So let’s fix it. First rename the /usr/lib/systemd/system/clamd@.service file.

Rename the clamd@ file.

mv /usr/lib/systemd/system/clamd@.service /usr/lib/systemd/system/clamd.service

Now we have to change the clamd@scan service as well, as it refers to a non-existing file now. Change this line in /usr/lib/systemd/system/clamd@scan.service and remove the @ sign.

.include /lib/systemd/system/clamd@.service

Next step is changing the clamd service file /usr/lib/systemd/system/clamd.service

[Unit]
Description = clamd scanner daemon
After = syslog.target nss-lookup.target network.target

[Service]
Type = simple
ExecStart = /usr/sbin/clamd -c /etc/clamd.d/clamd.conf --foreground=yes
Restart = on-failure
PrivateTmp = true

[Install]
WantedBy=multi-user.target

Move into the directory.

cd /usr/lib/systemd/system

Start all services.

# systemctl enable clamd.service  
# systemctl enable clamd@scan.service  
# systemctl start clamd.service  
# systemctl start clamd@scan.service

Checking the status

With all these changes, ClamAV on CentOS 7 should be running now. The easiest way to check, is using the ps command and see if freshclam and clamd are running.

Useful resources for debugging are the systemctl status command, followed by the service. Then there is logging in /var/log/messages, which usually will reveal when and why something is (not) running.

More tips? Let it know!

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