i'm also seeing this, and the solution was to comment out the (identity ...) field of my machine-ssh-configuration.
maybe my id_ed25519 key is not supported? it seems to be able to talk to the target and even installed some stuff into its store, and only dies when it's already deep into the process. BTW, the configuration field names and doc are somewhat confusing. e.g. the identity field expects a file path as a string; i.e. a file-like GEXP object doesn't work, and neither does a copy-pasted public key as a scheme string. also, should it be the .pub part, or the private part? maybe a pitfall pointer could be added to the manual until the error message is made more edifying? - attila PS: my output when it failed for me: $ guix deploy lendvai.scm The following 1 machine will be deployed: lendvai guix deploy: deploying to lendvai... guix deploy: sending 0 store items (0 MiB) to 'lendvai.name'... guix deploy: sending 0 store items (0 MiB) to 'lendvai.name'... guix deploy: sending 0 store items (0 MiB) to 'lendvai.name'... guix deploy: sending 0 store items (0 MiB) to 'lendvai.name'... ;;; [2022/12/21 22:16:19.061054, 0] [GSSH ERROR] Channel opening failure: channel 63 error (2) open failed: #<input-output: channel (closed) 7ff538de42e0> Backtrace: In guix/store.scm: 1382:11 19 (map/accumulate-builds #<store-connection 256.99 7ff53be77a50> …) 1300:8 18 (call-with-build-handler #<procedure 7ff5387f3a20 at guix/sto…> …) In ice-9/boot-9.scm: 1752:10 17 (with-exception-handler _ _ #:unwind? _ #:unwind-for-type _) In guix/scripts/deploy.scm: 167:6 16 (_) In guix/store.scm: 2170:25 15 (run-with-store #<store-connection 256.99 7ff53be77a50> _ # _ # …) In gnu/machine/ssh.scm: 538:12 14 (_ _) 539:41 13 (_ _) In ice-9/boot-9.scm: 1752:10 12 (with-exception-handler _ _ #:unwind? _ #:unwind-for-type _) In gnu/machine/ssh.scm: 539:41 11 (_) In guix/store.scm: 2170:25 10 (run-with-store #<store-connection 256.99 7ff53823e910> #<pro…> …) In guix/remote.scm: 138:10 9 (_ _) In guix/store.scm: 2042:38 8 (_ #<store-connection 256.99 7ff53823e910>) In guix/ssh.scm: 376:2 7 (send-files #<store-connection 256.99 7ff53823e910> _ #<store…> …) 222:5 6 (remote-run (begin (use-modules (guix) (srfi srfi-34) (…) …) …) …) In ssh/popen.scm: 64:4 5 (open-remote-pipe* _ "r+" _ . _) In unknown file: 4 (channel-open-session #<input-output: channel (closed) 7ff538d…>) In ice-9/boot-9.scm: 1685:16 3 (raise-exception _ #:continuable? _) 1683:16 2 (raise-exception _ #:continuable? _) 1685:16 1 (raise-exception _ #:continuable? _) 1685:16 0 (raise-exception _ #:continuable? _) ice-9/boot-9.scm:1685:16: In procedure raise-exception: Throw to key `guile-ssh-error' with args `("channel-open-session" "Channel opening failure: channel 63 error (2) open failed" #<input-output: channel (closed) 7ff538de42e0> #f)'.