Custom destinations are destintations that are not build-in into uback,
but implemented by an external command, typicall a script, under the
control of the user.
When creating a backup, you give command as the destination type,
and set the @Command option to the custom source command. It can be
either a full path or relative path if the custom destination command
in in the PATH.
$ uback backup $SOURCE_OPTIONS id=test,type=command,command=uback-fs-destThe first argument passed to the command is the kind of command: source
for a source, and destination for a destination. In the context of
this document, the first argument will always be destination.
uback passes the requested operation and arguments as the next arguments
on the command line, and options passed to the destination as environment
variable. For example, the SnapshotsPath will be translated into the
UBACK_OPT_SNAPSHOTS_PATH environment variable. If the option is a
slice option (for example @AdditionalArguments), it will be passed into
UBACK_SOPT_ADDITIONAL_ARGUMENTS, and the value will be a JSON-serialized
string array (the S in SOPT stands for "slice").
A custom destination command should follow the usual external process
conventions : use stdout for normal output that will be consumed by
uback, use stdin for normal input that will be given by uback,
use stderr to print free-format messages destined to the end user. An
exit code of 0 indicates a successful operation, whereas a non-zero one
indicates a failure.
A destination must implement those operations, which will be described in the next sections :
- validate-options
- list-backups
- remove-backup
- send-backup
- receive-backup
This operation takes no argument ; it is called before any other operation and should be used to validate options.
This operation takes no argument, and should print all backups currently
present on the destination, one per line. You can either
give a backup name (20210102T000000.000-full) or a filename
(20210102T000000.000-full.ubkp).
For convenience purposes, lines starting with a . or _ are ignored.
This operation takes one argument, the full
name of a backup (20210102T000000.000-full or
20210102T000000.000-from-20210101T000000.000), and should remove the
backup on the destination.
This operation takes one argument, the full name of a backup. uback
will provide the backup to the command standard input ; the command
should store it.
This operation takes one argument, the full name of a backup. The command should output the backup on its standard output.
As an example, you can look at the uback-fs-test test script, which reimplement the fs destination as a bash script.