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Windows will not react to dynamically set environment variables (e.g: `process.env.MOUNTUTILS_DEBUG = '1'`), so in order to workaround this limitation, we set `MOUNTUTILS_DEBUG` in `lib/child-writer/writer-proxy.js` when spawning the CLI, and we also set `DEBUG='*'` in `lib/start.js`, so it gets picked up by the child writer module, which spawns the writer proxy by inheriting the environment.
Etcher CLI
The Etcher CLI is a command line interface to the Etcher writer backend, and currently the only module in the "Etcher" umbrella that makes use of this backend directly.
This module also has the task of unmounting the drives before and after flashing.
Notice the Etcher CLI is not worried about elevation, and assumes it has enough
permissions to continue, throwing an error otherwise. Consult the
lib/child-writer module to understand how elevation works on
Etcher.
The robot option
Setting the ETCHER_CLI_ROBOT environment variable allows other applications
to easily consume the output of the Etcher CLI in real-time. When using the
ETCHER_CLI_ROBOT option, the --yes option is implicit, therefore you need
to manually specify --drive.
When ETCHER_CLI_ROBOT is used, the program will output JSON lines containing
the progress state and other useful information. For example:
$ sudo ETCHER_CLI_ROBOT=1 etcher image.iso --drive /dev/disk2
{"command":"progress","data":{"type":"write","percentage":1,"eta":130,"speed":1703936}}
...
{"command":"progress","data":{"type":"check","percentage":100,"eta":0,"speed":17180514}}
{"command":"done","data":{"sourceChecksum":"27c39a5d"}}
See documentation about the robot mode at lib/shared/robot.
Exit codes
The Etcher CLI uses certain exit codes to signal the result of the operation.
These are documented in lib/shared/exit-codes.js and are also
printed on the Etcher CLI help page.