Debugging Secure File Transfer

The secure file transfer process (sft-server-g3) is debugged together with the Tectia Server, and the same debug level that is set for Tectia Server (ssh-server-g3) is used for both processes.

By default, the sft-server-g3 debug messages are sent to the standard error, that goes also to the SFTP client. If you want to forward the sft-server-g3 debug messages into a file and not to the client, you can add the following two environment variables affecting the secure file transfer user into the /etc/environment file on Unix and into the user-specific environment variables on Windows:

SSH_SFTP_DEBUG defines the debug level that controls the messages that the sft-server-g3 process will be showing while executing. This variable can be used when no debug level has been set for the sft-server-g3 process. The value can be for example:
```
SSH_SFTP_DEBUG=SftpLibServer=80,SftpLibStageFsFile=80
```
If debug level is set for ssh-server-g3 this variable will be ignored.
SSH_SFTP_DEBUG_FILE defines the file where the debug messages from the sft-server-g3 will be printed. This variable can be used when no debug level has been set for the sft-server-g3 process. The value can be for example:
```
SSH_SFTP_DEBUG_FILE=/tmp/sft_debug.txt
```
If this variable is not defined, the messages will be sent to standard error as normally, and the SFTP client will receive them.
If debug level is set for ssh-server-g3 this variable will be ignored.