How do we update ClamAV definitions

We have a system on an isolated network. We are running ClamAV.

How do we download the (ClamAV virus definitions) .cvd files or whatever they are called so that we can put them on media (USB memory stick, CD/DVD)?

Hi @warron.french,

Download with a browser (I used FF, it doesn’t work with wget) the following three files:
same link /bytecode.cvd

(sorry for the last one, but as a new user I’m not allowed to put more than 2 links in a post)

Copy them on /var/lib/clamav (hint: take care to not use “preserve attributes” of the files on the USB stick when overwriting the existing ones on the system).


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@bogdan_ro , thank you. I will try this at work.

@bogdan_ro , can you tell me how often ClamAV updates those 3 definition files, if you know?

More specifically is it at least once per week, or generally once every 2 weeks?
Since they are not a big brand name like McAfee, Symantec, etc… what is their rhythm for updating those CVD files?

Thanks in advance,

Hi @warron.french,

It’s actually daily… Hence the name of one of the 3 files “daily.cvd”.

However, as long as the system is isolated from the internet, I would say it’s OK from a security point of view to update less frequently the antivirus definitions.

Or, if you really need a daily update, a solution would be to write an udev rule to match a specific partition label of a USB stick containing the update files (and execute a script to update the antivirus files) automatically when you insert a specific USB key, without the need to do these operations by hand (login, mount USB stick, overwrite files, unmount, etc…).


I think the correct procedure would be:

  • run freshclam which comes with its own systemd service
  • copy the entire folder /var/lib/clamav/ to your portable media
  • replace the old /var/lib/clamav/ with the new one on your offline system

Please avoid directly downloading the signature files, it is better to use the freshclam tool because it handles various aspects of error codes, load balancing, etc.

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Good morning,
I’m intruding in the conversation :slight_smile: but you talk about clamav and I wonder if it happened to you or not ?
This is a mistake:

Failed to start clamd scanner (multi-user) daemon.

I have not experienced this, at least not yet.

There are some who say on other forums that it is related to SELINUX but when I make their order they always put me the error

Je regrets @Link_Darck , je ne comprends pas -

Can you reword your statement please?

Do you mean others have indicated SELINUX could be the problem? Have you attempted to disable SELINUX temporarily to observe whether the problem will go away? Doing this is a good test to quickly determine if SELINUX is the problem or not.

If it is the problem, then keep SELINUX running in enforced or permitted mode, and then alter the context(s) appropriately using semanage.

Also, what do you mean by “they always put me the error?”

I think your post is lost in translation from French to English. Je me regrets.