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SSH File Transfer Protocol

SFTP is a protocol that works over SSH to transfer and manage files over the network. Is not the same as FTP or FTPS, but its similar. Most servers have enabled the SFTP mode if they have a SSH server. OpenSSH implementation have the SFTP module and can be enabled if desired.

In order to connect to a SFTP server and use it as provider, the host and user must be defined, and use one of the following authentication methods.

The backupPath must exist in the server, and the user must have write permissions on it.

The authentication is attempted using the following order:

  • If privateKey or privateKeyFile is defined, then this method will be used. If the private key is cyphered, use password as the passphrase of the key.
  • If allowAgent is true, then will use the SSH Agent to connect to the server.
  • Any key found in ~/.ssh.
  • If the password is defined, then the classic username/password login will be used (discouraged).

The known-hosts list is loaded by default from the default location ~/.ssh/known_hosts. If hostKeysFilePath is defined, then this file will be used instead. If enableHostKeys is set to false, then no known-hosts will be loaded.

The knownHostsPolicy will set the policy that will be used when the SSH connection is set, but the host is being checked as a known or not-known host. The following policies are allowed:

  • reject will close the connection if the host is not-known (default behaviour).
  • auto-add will add to the list of known-hosts if the host is not-known.
  • ignore will print a warning if the host is not-known.

Note: if the knownHostsPolicy is auto-add and hostKeysFilePath is defined, then the new host will be saved into the file.


In order to use SFTP, you must install the following python packages:

  • paramiko

Configuration schema

  "type": "sftp",
  "backupsPath": "Path in the SFTP where the backups will be located",
  "maxBackupsKept": "Indicates how many backups to keep in this storage, or set to null to keep them all",
  "host": "Host where the SFTP server is located",
  "port": "(optional) Port of the SFTP server (by default 22)",
  "user": "User to connect to the SFTP server",
  "password": "(optional) Password for the user",
  "privateKey": "(optional) Private Key in base64",
  "privateKeyPath": "(optional) Private Key file path",
  "allowAgent": "(optional) if true, then the connection will interact with the SSH Agent, false if this behaviour is not desired (false by default)",
  "compress": "(optional) if true, then the connection is compressed (false by default)",
  "knownHostsPolicy": "(optional) Changes the Known Hosts Policy. 'reject' will reject any connection to a server that is not known (default behaviour), 'auto-add' will add to the known-hosts list this server, 'ignore' will print a warning but it will let you connect.",
  "hostKeysFilePath": "(optional) Path to the known-hosts file",
  "enableHostKeys": "(optional) If set to false, it won't load any known-hosts file (by default is true)"