For RedHat Enterprise Linux you need to install HPLIP manually:
There is also the link to download the hplip-3.12.11_rhel-6.0.x86:64.rpm package.
Impotant: The hplip version that is provided by the RedHat Package manager is in version 3.10.9. That version DOES NOT support the DeskJet 3050a!
I used the installation manual from the link above. At Step 3 (Installing rpm package) I got the error :
file /usr/lib64/libhpip.so.0.0.1 from install of hplipfull-3.12.11-0.x86_64 conflicts with file from package hplip-libs-3.10.9-3.el6.x86_64
To solve this, I used the –replaceFiles parameter:
Then you can find the printer by specifying the IP: