For using this plugin you need unrar library. You can download it from
http://www.rarlab.com/rar_add.htm
Windows:
Download "UnRAR.dll" - Self-extracting archive UnRARDLL.exe, unpack it
and copy unrar.dll in Double Commander (or %windir%\system32) directory
Linux:
Download "UnRAR source" unrarsrc-x.x.x.tar.gz, unpack it:
$ tar -xf unrarsrc-x.x.x.tar.gz
go to "unrar" directory:
$ cd unrar
make symlink makefile.unix -> makefile:
$ ln -s makefile.unix makefile
set CXX environment variable to "g++ -DSILENT"
$export CXX="g++ -DSILENT"
and build library:
$ make lib
After compiling, copy "libunrar.so" in "/usr/lib" directory:
$ cp libunrar.so /usr/lib/libunrar.so