by swamswam_h » Wed Sep 19, 2012 1:04 pm
There is of course the FreeNAS project. Which is essentially what you are asking for. A highly customizable and very powerful open source NAS 'distribution'. Beware though: the required specs for version 8 are enormous (ZFS filesystem). Version 7 is somewhat lighter. There has been a fork in the project. Version 8 is a sort of commercially adapted version (slowly moving to closed source / private development). Version 7 (0.7) has branched away from the trend of high-end hardware in freeNAS development towards more 'realistic' hardware requirements. Well.. a bit too simple, but the key here is: there are two versions. Freenas 7 and 8 and Freenas 7 has a re-development elsewhere (forgot the name). I have a NAS running on a dualcore atom with 2Gb ram using freenas 7. Works perfect.
Other 'NAS operating systems' are NASlite for instance (commercial product with a freeware 'light' version)