Can't pull anything with ADB = can't make backup

[garsnarge]

I want to back up my Nexus 5 install of 15.04 (installed last year by the UBports installer) so I can use Android for a couple weeks. I've got a lot of data that I'll want to restore.

running "$ adb pull /home" while logged in with dev mode on in the phone results in adb building the file list and then returning an error "failed to copy" a random file due to "no such device or address."

I reset to the ubports recovery and "$ adb pull /data/system-data" gets it building the file list and then error "failed to copy /data/system-data/var/log/installer/media-info" because "no such file or directory."

I jump into shell and navigate to ./installer and verify that media-info is in fact there. Try to pull it with the whole path specified, adb still insists it isn't there.

There is not apparently any way to make a backup directly from the ubports recovery. How can I back up my data?