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   systemd.unit    ( 5 )

конфигурация агрегата (Unit configuration)

STRING ESCAPING FOR INCLUSION IN UNIT NAMES

Sometimes it is useful to convert arbitrary strings into unit
       names. To facilitate this, a method of string escaping is used,
       in order to map strings containing arbitrary byte values (except
       NUL) into valid unit names and their restricted character set. A
       common special case are unit names that reflect paths to objects
       in the file system hierarchy. Example: a device unit
       dev-sda.device refers to a device with the device node /dev/sda
       in the file system.

The escaping algorithm operates as follows: given a string, any "/" character is replaced by "-", and all other characters which are not ASCII alphanumerics, ":", "_" or "." are replaced by C-style "\x2d" escapes. In addition, "." is replaced with such a C-style escape when it would appear as the first character in the escaped string.

When the input qualifies as absolute file system path, this algorithm is extended slightly: the path to the root directory "/" is encoded as single dash "-". In addition, any leading, trailing or duplicate "/" characters are removed from the string before transformation. Example: /foo//bar/baz/ becomes "foo-bar-baz".

This escaping is fully reversible, as long as it is known whether the escaped string was a path (the unescaping results are different for paths and non-path strings). The systemd-escape(1) command may be used to apply and reverse escaping on arbitrary strings. Use systemd-escape --path to escape path strings, and systemd-escape without --path otherwise.