_Note_: LLVM is also an optional dependency. LLVM will not provide any additional features, but is an alternative method for executing bytecode signatures versus using the built-in bytecode interpreter. Limited performance testing between LLVM and the bytecode interpreter did not yield conclusive evidence that one is "better" than the other. For the sake of simplicity, it is not recommended to install LLVM.
## Download the latest stable release
1. Open a browser and navigate to [the ClamAV downloads page](http://www.clamav.net/downloads)
2. Click `clamav-<version>.tar.gz` link to download the latest stable release.
## Extract the source archive
```bash
cd ~/Downloads
tar xzf clamav-<ver>.tar.gz
cd clamav-<ver>.tar.gz
```
## Configure the build
ClamAV's configure script should detect each of the above dependencies automatically.
### Typical `./configure` usage
```bash
./configure --enable-check
```
Once `./configure` completes, it will print a summary. Verify that the packages you installed are in fact being detected.
Example configure summary output:
```bash
configure: Summary of detected features follows
OS : linux-gnu
pthreads : yes (-lpthread)
configure: Summary of miscellaneous features
check : -lcheck_pic -pthread -lrt -lm -lsubunit
fanotify : yes
fdpassing : 1
IPv6 : yes
configure: Summary of optional tools
clamdtop : -lncurses (auto)
milter : yes (disabled)
clamsubmit : yes (libjson-c-dev found at /usr), libcurl-devel found at /usr)
configure: Summary of engine performance features
release mode: yes
llvm : no (disabled)
mempool : yes
configure: Summary of engine detection features
bzip2 : ok
zlib : /usr
unrar : yes
preclass : yes (libjson-c-dev found at /usr)
pcre : /usr
libmspack : yes (Internal)
libxml2 : yes, from /usr
yara : yes
fts : yes (libc)
```
### Additional popular `./configure` options
*`--with-systemdsystemunitdir` - Do not install `systemd` socket files. This option disables systemd support, but will allow you to `make install` to a user-owned directory without requiring `sudo`/root privileges:
```bash
./configure --with-systemdsystemunitdir=no
```
*`--sysconfdir` - Install the configuration files to `/etc` instead of `/usr/local/etc`:
```bash
./configure -–sysconfdir=/etc
```
*`--prefix` - Install ClamAV to a directory other than `/usr/local/`:
* Example 1: Install to a local `./install` directory.
```bash
./configure --prefix=`pwd`/install
```
* Example 2: Install ClamAV locally on an unprivileged shell account.
*`--disable-clamav` - _Don't_ drop super-user priveleges to run `freshclam` or `clamd` as the `clamav`* user.
```bash
./configure --disable-clamav
```
*_Tip_: Using this `--disable-clamav` means that `freshclam` and `clamd` will run with _root privleges_ if invoked using `sudo`. Running `clamd` or `clamscan` as root is **not recommended**. Instead of using this option, you can configure `freshclam` or `clamd` to drop to any other user by:
* setting the `DatabaseOwner` option in `freshclam.conf` and
* setting the `User` option in `clamd.conf`.
Please see the `./configure --help` for additional options.
### Compile ClamAV
Compile ClamAV with:
```bash
make -j2
```
### Run ClamAV Unit Tests (Optional)
For peace of mind, it can be helpful to run a small suite of unit and system tests.
Run:
```bash
make check
```
All tests should pass.* Output will look something like this:
* The `*.vg.sh` tests will be skipped unless you run `make check VG=1`.
* The `check7_clamd.hg.sh` (helgrind) is presently disabled and will be skipped.
* For details, see: [the Git commit](https://github.com/Cisco-Talos/clamav-devel/commit/2a5d51809a56be9a777ded02969a7427a3c26713)
If you have a failure or an error in the unit tests, it could be that you are missing one or more of the prerequisites.
If you are investigating a failure, please do the following:
`cd unit_tests`
Use `less` to read the log for the failed test.
Example:
```bash
less check4_clamd.sh.log`
```
To submit a bug report regarding unit text failures, please follow these [bug reporting steps](../Installation-Unix.md#Reporting-a-unit-test-failure-bug).
### Install ClamAV
Install ClamAV with:
```bash
make install
```
_Tip_: If installing to the default or other system-owned directory, you may need to use `sudo`.
### First time set-up
_Note_: The following instructions assume you used the default install paths (i.e. `/usr/local`). If you modified the install locations using `--prefix` or `--sysconfdir` options, replace `/usr/local` with your chosen install path.
#### `freshclam` config
Before you can use `freshclam` to download updates, you need to create a `freshclam` config. A sample config is provided for you.
1. Copy the sample config. You may need to use `sudo`:
2. Modify the config file using your favourite text editor. Again, you may need to use `sudo`.
* At a minimum, remove the `Example` line so `freshclam` can use the config.
Take the time to look through the options. You can enable the sample options by deleting the `#` comment characters.
Some popular options to enable include:
*`LogTime`
*`LogRotate`
*`NotifyClamd`
*`DatabaseOwner`
3. Create the database directory. *Tip: _You may need to use `sudo`._
```bash
mkdir /usr/local/share/clamav
```
#### `clamd` config (optional)
You can run `clamscan` without setting the config options for `clamd`. However, the `clamd` scanning daemon allows you to use `clamdscan` to perform faster a-la-carte scans, allows you to run multi-threaded scans, and allows you to use `clamav-milter` if you want to use ClamAV as a mail filter if you host an email server.
Additionally, if you are a running modern versions of Linux where the FANOTIFY kernel feature is enabled, `clamd` has a feature run with On-Access Scanning*. *When properly configured*, On-Access Scanning can scan files as they are accessed and optionally block access to the file in the event that a signature alerted.
_Note_: At this time, for On-Access Scanning to work, `clamd` must run with `sudo`/root privileges. For more details, please see our documentation on On-Access Scanning.
1. Copy the sample config. You may need to use `sudo`:
2. Modify the config file using your favourite text editor. Again, you may need to use `sudo`.
* At a minimum, remove the `Example` line so `freshclam` can use the config.
* You also _need_ to select a Socket option for `clamd` so `clamdscan` and other utilities can communicate with `clamd`. You must enable _one_ of the following.
*`LocalSocket`
*`TCPSocket`
Take the time to look through the options. You can enable the sample options by deleting the `#` comment characters.
Some popular options to enable include:
*`LogTime`
*`LogClean`
*`LogRotate`
*`User`
*`ScanOnAccess`
*`OnAccessIncludePath`
*`OnAccessExcludePath`
*`OnAccessPrevention`
#### Configure SELinux for ClamAV
Certain distributions (notably RedHat variants) when operating with SELinux enabled use the non-standard `antivirus_can_scan_system` SELinux option instead of `clamd_can_scan_system`.
At this time, libclamav only sets the `clamd_can_scan_system` option, so you may need to manually enable `antivirus_can_scan_system`. If you don't perform this step, freshclam will log something like this when it tests the newly downloaded signature databases:
To allow ClamAV to operate under SELinux, run the following:
```bash
setsebool -P antivirus_can_scan_system 1
```
#### Download / Update the signature database
Before you can run a scan, you'll need to download the signature databases. Once again, you may need to run with `sudo`/root privileges.
If you installed to a location in your system PATH:
```bash
freshclam
```
If you installed to another location:
```bash
/<path>/<to>/<clamav>/<bin>/freshclam
```
_Important_: It is common on Ubuntu after a fresh install to see the following error the first time you use ClamAV:
```bash
$ freshclam
freshclam: error while loading shared libraries: libclamav.so.7: cannot open shared object file: No such file or directory
```
You can fix this error by using ldconfig to rebuild the library search path.
```bash
sudo ldconfig
```
#### Users and on user privileges
If you are running `freshclam` and `clamd` as root or with `sudo`, and you did not explicitely configure with `--disable-clamav`, you will want to ensure that the `DatabaseOwner` user specified in `freshclam.conf` owns the database directory so it can download signature udpates.
The user that `clamd`, `clamdscan`, and `clamscan` run as may be the same user, but if it isn't -- it merely needs _read_ access to the database directory.
If you choose to use the default `clamav` user to run `freshclam` and `clamd`, you'll need to create the clamav group and the clamav user account the first time you install ClamAV.
