disksig

Overview ¶

Package disksig recognises what a disk already holds, so that nothing in GoNIX formats a disk that is not blank.

Init formats the persist device, the datadisk service formats the data disk and a Library image's init formats /data, each when the disk will not mount. A mount fails for many reasons besides blankness — another filesystem, a partition table, the wrong device named on the command line, an I/O error — and formatting in any of those cases destroys whatever was there. So each of them asks Probe first and formats only when it finds nothing.

The checks follow blkid's: a magic number at a fixed offset. A filesystem this package does not know (ZFS, say) reads as blank.