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| -rw-r--r-- | src/guestfs.pod | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/src/guestfs.pod b/src/guestfs.pod index c235383c..d034c8e3 100644 --- a/src/guestfs.pod +++ b/src/guestfs.pod @@ -747,6 +747,37 @@ fuse/guestmount.c. In libguestfs 1.5.4, the protocol was changed so that the Linux errno is sent back from the daemon. +=item Ambiguity between devices and paths + +There is a subtle ambiguity in the API between a device name +(eg. C</dev/sdb2>) and a similar pathname. A file might just happen +to be called C<sdb2> in the directory C</dev> (consider some non-Unix +VM image). + +In the current API we usually resolve this ambiguity by having two +separate calls, for example L</guestfs_checksum> and +L</guestfs_checksum_device>. Some API calls are ambiguous and +(incorrectly) resolve the problem by detecting if the path supplied +begins with C</dev/>. + +To avoid both the ambiguity and the need to duplicate some calls, we +could make paths/devices into structured names. One way to do this +would be to use a notation like grub (C<hd(0,0)>), although nobody +really likes this aspect of grub. Another way would be to use a +structured type, equivalent to this OCaml type: + + type path = Path of string | Device of int | Partition of int * int + +which would allow you to pass arguments like: + + Path "/foo/bar" + Device 1 (* /dev/sdb, or perhaps /dev/sda *) + Partition (1, 2) (* /dev/sdb2 (or is it /dev/sda2 or /dev/sdb3?) *) + Path "/dev/sdb2" (* not a device *) + +As you can see there are still problems to resolve even with this +representation. Also consider how it might work in guestfish. + =back =head2 PROTOCOL LIMITS |