ssh-copy-id hanging sometimes

Question

This is a "follow up" to my question from last week. Basically I am seeing that some python code that ssh-copy-id using pexpect occasionally hangs.

I thought it might be a pexect problem, but I am not so sure any more after I was able to collect a "stacktrace" from such a hang. Here you can see some traces from my application; followed by the stack trace after running into the timeout:

2016-07-01 13:23:32 DEBUG           copy command: ssh-copy-id -i /yyy/.ssh/id_rsa.pub [email protected]
2016-07-01 13:23:33 DEBUG           first expect: 1
2016-07-01 13:23:33 DEBUG           sending PASSW0RD
2016-07-01 13:23:33 DEBUG           consuming output from remote side ... 
2016-07-01 13:24:03 INFO            Timeout occured ... stack trace information ...

2016-07-01 13:24:03 INFO            Traceback (most recent call last):


File "/usr/local/lib/python3.5/site-packages/pexpect-3.3-py3.5.egg/pexpect/__init__.py", line 1535, in expect_loop
c = self.read_nonblocking(self.maxread, timeout)
File "/usr/local/lib/python3.5/site-packages/pexpect-3.3-py3.5.egg/pexpect/__init__.py", line 968, in read_nonblocking
raise TIMEOUT('Timeout exceeded.')
pexpect.TIMEOUT: Timeout exceeded.

During handling of the above exception, another exception occurred:
Traceback (most recent call last):
 File "xxx/PrepareSsh.py", line 28, in execute
   self.copy_keys(context, user, timeout)
 File "xxx/PrepareSsh.py", line 83, in copy_keys
   child.expect('[#\$]')
 File "/usr/local/lib/python3.5/site-packages/pexpect-3.3-py3.5.egg/pexpect/__init__.py", line 1451, in expect
timeout, searchwindowsize)
 File "/usr/local/lib/python3.5/site-packages/pexpect-3.3-py3.5.egg/pexpect/__init__.py", line 1466, in expect_list
timeout, searchwindowsize)
 File "/usr/local/lib/python3.5/site-packages/pexpect-3.3-py3.5.egg/pexpect/__init__.py", line 1568, in expect_loop
raise TIMEOUT(str(err) + '\n' + str(self))
pexpect.TIMEOUT: Timeout exceeded.
<pexpect.spawn object at 0x2b74694995c0>
version: 3.3
command: /usr/bin/ssh-copy-id
args: ['/usr/bin/ssh-copy-id', '-i', '/yyy/.ssh/id_rsa.pub', '[email protected]']
searcher: <pexpect.searcher_re object at 0x2b746ae1c748>
buffer (last 100 chars): b'\r\n/usr/bin/xauth:  creating new authorityy file /home/hmcmanager/.Xauthority\r\n'
before (last 100 chars): b'\r\n/usr/bin/xauth:  creating new authority file /home/hmcmanager/.Xauthority\r\n'
after: <class 'pexpect.TIMEOUT'>

So, what I find kinda strange: xauth showing up in the messages that pexpect received.

You see, today, I created another VM for testing; and did all the setup manually. This is what I see when doing so:

> ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected]

 /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/xxx/.ssh/id_rsa.pub"
The authenticity of host 'some.ip (some.ip)' can't be established.
ECDSA key fingerprint is SHA256:7...
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
[email protected]'s password: 
Number of key(s) added: 1
Now try logging into the machine, with:   ....

So, lets recap:

• when I run ssh-copy-id manually ... everything works; and the string "xauth" doesn't show up in the output coming back
• when I run ssh-copy-id programmatically, it works most of the time; but sometimes there are timeouts ... and that message about xauth is send to my client

This is driving me crazy. Any ideas are welcome.

Answer 1

xauth reference smells like you are requesting X11 Forwarding. It will be configured in your ~/.ssh/config. That might be the difference in your configuration that can cause the hangs.