Actual API is implemented in the `init`, as it has access to root
filesystem. `osd` proxies API back to `init` with some tricks to support
grpc streaming.
Given some absolute path, `init` produces and streams back .tar.gz
archive with filesystem contents.
`osctl cp` works in two modes. First mode streams data to stdout, so
that we can do e.g.: `osctl cp /etc - | tar tz`. Second mode extracts
archive to specified location, dropping ownership info and adjusting
permissions a bit. Timestamps are not preserved.
If full dump with owner/permisisons is required, it's better to stream
data to `tar xz`, for quick and dirty look into filesystem contents
under unprivileged user it's easier to use in-place extraction.
Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>
