* Unclear `btrfs subvolume snapshot` command
@ 2018-04-16 12:45 Stefan Klinger
0 siblings, 0 replies; only message in thread
From: Stefan Klinger @ 2018-04-16 12:45 UTC (permalink / raw)
To: linux-btrfs
Hi,
I'm using
# btrfs version
btrfs-progs v4.16
In btrfs-subvolume(8), I find the description of the `snapshot`
command unclear:
snapshot [-r] <source> <dest>|[<dest>/]<name>
I find the preference of `|` is unclear. From the text passage
If only <dest> is given, the subvolume will be named the basename
of <source>.
I infer, that `<source>` must be there even “if only <dest> is given”.
Also, it's unclear how the cases
snapshot [-r] <source> <dest>
snapshot [-r] <source> [<dest>/]<name>
are told apart. I assume it's based on whether `<dest>` is an
existing directory. I came to this from the rather unfortunate error
message
ERROR: invalid snapshot name '/'
when trying
# btrfs subvolume snapshot / /foo
where `/foo` already existed. It took me some time to arrive at the
conclusion that `btrfs` took this as the `<source> <dest>` case, and
tried to make a subdir `/` under `/foo`, which is, of course, illegal.
May I suggest the following changes:
* in the manual, change to:
snapshot [-r] <source> <dest>
Create a snapshot of the subvolume <source>.
If <dest> is an existing directory, the snapshot will be
named <dest>/<basename of source>. Note that this is
illegal if <source> is `/`.
If <dest> does not exist, it will be created, and this
will be the snapshot.
* in `btrfs subvolume`: Change the error message from
ERROR: invalid snapshot name '/'
to
ERROR: '<dest>' exists, but cannot create snapshot named '/'
under it. Specify explicit snapshot name.
IMHO it would be better to replace an existing <dest> with the
snapshot, instead of creating one under it. It would solve above
problem, and also be more similar to how `mount` handles a mountpoint.
Thank you,
Stefan
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