Create passwordless.md

docs/compute/passwordless.md

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+## Transferring data to CURC without a password (_command line only_)
+
+_Note: you must be logged in to [campus VPN](https://oit.colorado.edu/services/network-internet-services/vpn) to do a passwordless data transfer to CURC_
+
+### generate an ssh keypair on your local laptop/desktop
+
+You only need to perform this step once. From a local terminal run:
+
+```
+ssh-keygen -t ed25519
+``` 
+
+This will create ~/.ssh/id_ed25519 and ~/.ssh/id_ed25519.pub on your local machine (_note: the "~" denotes your home directory). 
+
+### Copy the public key to ~/.ssh/authorized_keys on a CURC login node 
+
+You only need to perform this step once. From a local terminal run:
+
+```
+cat ~/.ssh/id_ed25519.pub | ssh ralphie@login.rc.colorado.edu -T "cat >> ~/.ssh/authorized_keys"
+```
+...where you should substitute your CURC username for "ralphie"; you will be required to enter your password and accept a Duo push in order to transfer the key.
+
+_Note: If you have trouble running the command above, you can also just login to a CURC login node, open `~/.ssh/authorized_keys` and paste the text from `~/.ssh/id_ed25519.pub` that resides on your local machine.
+
+### Use `rsync` or `scp` to transfer files without a password
+
+Now you are ready to transfer files.  Make sure you are logged on campus or logged into CU VPN. 
+
+For example, to tranfer a `myfile.txt` from your local machine to your `/projects/$USER` directory on CURC
+
+```
+rsync -av ./myfile.txt dtn-new-data.rc.int.colorado.edu:/projects/ralphie/myfile.txt
+```
+
+or, you can use scp.  Here user `ralphie` transfers to a PetaLibrary allocation called "crdds" that Ralphie has access to:
+
+```
+scp ./myfile.txt dtn-new-data.rc.int.colorado.edu:/pl/active/crdds/myfile.txt
+```