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I am trying to get some information from a Nokia router over ssh from a Linux machine.

The ssh works fine if I do this:

ssh admin@10.0.0.1

I can enter the password, log in, run commands.

However when I do the following, it disconnects me immediately:

ssh -v admin@10.0.0.1 'show time'

Verbose output:
debug1: Next authentication method: password
admin@10.0.0.1's password: 
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: Sending environment.
debug1: Sending env LC_PAPER = en_US.UTF-8
debug1: Sending env LC_ADDRESS = en_US.UTF-8
debug1: Sending env LC_MONETARY = en_US.UTF-8
debug1: Sending env LC_NUMERIC = en_US.UTF-8
debug1: Sending env LC_TELEPHONE = en_US.UTF-8
debug1: Sending env LC_IDENTIFICATION = en_US.UTF-8
debug1: Sending env LANG = en_US.UTF-8
debug1: Sending env LC_MEASUREMENT = en_US.UTF-8
debug1: Sending env LC_TIME = en_US.UTF-8
debug1: Sending env LC_NAME = en_US.UTF-8
debug1: Sending command: show time
debug1: channel 0: free: client-session, nchannels 1
Connection to 10.0.0.1 closed by remote host.
Transferred: sent 2088, received 1840 bytes, in 0.0 seconds
Bytes per second: sent 488193.7, received 430209.0
debug1: Exit status -1

It works fine if I use an expect script to connect, send password, and then send the command.

What could be wrong?

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  • It really depends on what ssh server that router is running, also whether it successfully sets path etc for non-interactive sessions. My suspicion is that it runs an old version of dropbear which is known to have similar issues. You'll have to give a bit more info on the make, model and OS version to get to the bottom of it, if it's at all possible. dropbear.ucc.asn.narkive.com/LsaFu4PH/non-interactive-commands suggests others have similar issues with old dropbear.
    – Alex Berry
    Jun 8 '17 at 11:02
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    alcatelunleashed.com/viewtopic.php?t=21551 A bit of googling shows an known issue and a workaround using a perl script, supplied by a third party. (Code review first to make sure it's not doing anything funky like sending your credentials off elsewhere).
    – Alex Berry
    Jun 8 '17 at 11:04
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Thanks for all the comments.

In the end I ended up using expect as I am using a bash script to connect and pull the information.

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