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I'm having trouble checking out a private git repository hosted on GitHub during a Docker image build. The error from SSH in verbose mode is:

OpenSSH_6.6.1, OpenSSL 1.0.1f 6 Jan 2014
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to github.com [192.30.252.130] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
debug1: Remote protocol version 2.0, remote software version libssh-0.6.0
debug1: no match: libssh-0.6.0
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-sha1 none
debug1: kex: client->server aes128-ctr hmac-sha1 none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: RSA 16:27:ac:a5:76:28:2d:36:63:1b:56:4d:eb:df:a6:48
debug1: read_passphrase: can't open /dev/tty: No such device or address
Host key verification failed.

The /dev/tty device does seem to be present:

total 4
drwxr-xr-x   4 root root     340 Jul 22 17:12 .
drwxr-xr-x 130 root root    4096 Jul 22 17:12 ..
lrwxrwxrwx   1 root root      13 Jul 22 17:12 fd -> /proc/self/fd
crw-rw-rw-   1 root root  1,   7 Jul 22 17:12 full
c---------   1 root root 10, 229 Jul 22 17:12 fuse
lrwxrwxrwx   1 root root      11 Jul 22 17:12 kcore -> /proc/kcore
crw-rw-rw-   1 root root  1,   3 Jul 22 17:12 null
lrwxrwxrwx   1 root root       8 Jul 22 17:12 ptmx -> pts/ptmx
drwxr-xr-x   2 root root       0 Jul 22 17:12 pts
crw-rw-rw-   1 root root  1,   8 Jul 22 17:12 random
drwxrwxrwt   2 root root      40 Jul 22 17:12 shm
lrwxrwxrwx   1 root root      15 Jul 22 17:12 stderr -> /proc/self/fd/2
lrwxrwxrwx   1 root root      15 Jul 22 17:12 stdin -> /proc/self/fd/0
lrwxrwxrwx   1 root root      15 Jul 22 17:12 stdout -> /proc/self/fd/1
crw-rw-rw-   1 root root  5,   0 Jul 22 17:12 tty
crw-rw-rw-   1 root root  1,   9 Jul 22 17:12 urandom
crw-rw-rw-   1 root root  1,   5 Jul 22 17:12 zero

Here is a stripped down version of my Dockerfile illustrating my test:

FROM ubuntu:trusty

ADD . /my_app
ADD ./config/ssh/docker_ssh_key /root/.ssh/id_rsa

RUN ls -al /dev
RUN ssh -t -t -v [email protected]

CMD bundle exec thin -p $PORT -R config.ru start

I have tested the build and know that the key does work. I can access the git repository just fine if I build the image without the RUN commands and start a container with an interactive shell.

I have found some other questions with similar errors messages. But they are for missing /dev/tty which doesn't seem to be the case here. Any ideas?

1
  • Does the private key (on either client or server) have a passphrase? If so, maybe try a test to see if using an unencrypted private key causes the same issue. It's not the most secure setup, but it might help you isolate the issue. Commented Jul 22, 2014 at 17:32

1 Answer 1

11

You need to accept the Github host key. Use ssh-keyscan:

ssh-keyscan -t rsa github.com 2>&1 >> /root/.ssh/known_hosts
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3 Comments

Thanks! I finally figured it was the prompt coming up to accept the host key. Accepting it manually suppresses this prompt and SSH continues.
Thank you. Necessary to realize git clone in a container docker without copy ~/.ssh/know_hosts.

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