az acs kubernetes get-credentials needs appended 'mgmt' to DNS prefix

When using the command from the Kubernetes tutorial to get credentials, it should be mentioned that the DNS prefix you specify when creating the container service and the one you need to specify when doing

az acs kubernetes get-credentials --dns-prefix=<...>

are not the same; it seems you must append mgmt to the latter. E.g., I create a Kubernetes Cluster with DNS prefix mykube, then I need to get the credentials using --dns-prefix=mykubemgmt, which is rather confusing.

Important: I created my Kubernetes cluster using the Portal directly, not via the az command line tooling (including creating my own Service Principal and such). This also means that my acs name was prefixed with containerservice-<what I wrote>.

The error message you get otherwise is just this (here on macOS Sierra):

[Errno 8] nodename nor servname provided, or not known
Traceback (most recent call last):
  File "/Users/myuser/Library/Python/2.7/lib/python/site-packages/azure/cli/main.py", line 34, in main
    cmd_result = APPLICATION.execute(args)
  File "/Users/myuser/Library/Python/2.7/lib/python/site-packages/azure/cli/core/application.py", line 139, in execute
    result = expanded_arg.func(params)
  File "/Users/myuser/Library/Python/2.7/lib/python/site-packages/azure/cli/core/commands/__init__.py", line 275, in _execute_command
    result = op(client, **kwargs) if client else op(**kwargs)
  File "/Users/myuser/Library/Python/2.7/lib/python/site-packages/azure/cli/command_modules/acs/custom.py", line 477, in k8s_get_credentials
    '.kube/config', path_candidate)
  File "/Users/myuser/Library/Python/2.7/lib/python/site-packages/azure/cli/command_modules/acs/acs_client.py", line 21, in SecureCopy
    ssh.connect(host, username=user, key_filename=os.path.join(home, '.ssh', 'id_rsa'))
  File "/Users/myuser/Library/Python/2.7/lib/python/site-packages/paramiko/client.py", line 296, in connect
    to_try = list(self._families_and_addresses(hostname, port))
  File "/Users/myuser/Library/Python/2.7/lib/python/site-packages/paramiko/client.py", line 200, in _families_and_addresses
    addrinfos = socket.getaddrinfo(hostname, port, socket.AF_UNSPEC, socket.SOCK_STREAM)
gaierror: [Errno 8] nodename nor servname provided, or not known

I also tried the client in docker (which uses Python 3.5); there the error message looks like this:

[Errno -2] Name does not resolve
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/site-packages/azure/cli/main.py", line 34, in main
    cmd_result = APPLICATION.execute(args)
  File "/usr/local/lib/python3.5/site-packages/azure/cli/core/application.py", line 142, in execute
    result = expanded_arg.func(params)
  File "/usr/local/lib/python3.5/site-packages/azure/cli/core/commands/__init__.py", line 275, in _execute_command
    result = op(client, **kwargs) if client else op(**kwargs)
  File "/usr/local/lib/python3.5/site-packages/azure/cli/command_modules/acs/custom.py", line 511, in k8s_get_credentials
    '.kube/config', path_candidate)
  File "/usr/local/lib/python3.5/site-packages/azure/cli/command_modules/acs/acs_client.py", line 21, in SecureCopy
    ssh.connect(host, username=user, key_filename=os.path.join(home, '.ssh', 'id_rsa'))
  File "/usr/local/lib/python3.5/site-packages/paramiko/client.py", line 296, in connect
    to_try = list(self._families_and_addresses(hostname, port))
  File "/usr/local/lib/python3.5/site-packages/paramiko/client.py", line 200, in _families_and_addresses
    addrinfos = socket.getaddrinfo(hostname, port, socket.AF_UNSPEC, socket.SOCK_STREAM)
  File "/usr/local/lib/python3.5/socket.py", line 732, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -2] Name does not resolve

So either this is a documentation thing, or the behavior of the az cli tool has changed, or both. Right now, I’d say it’s confusing.

Update: It works (with the changes I made in a PR) if you create the cluster using the az command line; so it seems the Container Services UI in the portal uses a different template than the az command line does.

[alex88]

Oh I see, I’ve

azure-cli (0.1.1b2)
acr (0.1.1b1)
acs (0.1.1b1)

anyway, I’ve downloaded the config file from the master machine and it’s now working, thanks

[jesushernandez]

The confusing part for me was the documentation, so 👍 (disclaimer: I can’t test that command right now, but I believe it just works as stated in the new documentation).