I have a embedded device (Perle IOLAN+, an Ethernet to serial adaptor) that I can administer via SSH. From time to time, I need to log in and execute a command on this device. Logging in via SSH, getting an interactive shell and running the command is all smooth and works well.
However, I wanted to automate the process, and have a script on my server log in and run this command for me periodically. I was testing to see if I could remote-execute via SSH and it seems I can't.
The command I want to run, which works fine via interactive shell, is
kill line *. On my server, I try
ssh user@device_host kill line *. But the expected result does not occur. when I try
ssh user@device_host uptime I don't get any output, even though
uptime on in the device's interactive shell works fine.
The device is not running a full, normal OS - it's some manner of embedded, striped-down *nix, with only very few commands available. I was wondering if its SSH server might not recognise remote command execution. Is there some way to check? Are pared-down SSH servers often lacking this feature?
Might there be another way to remote-execute a command without going in through an interactive shell?
Output of ssh with -vv is:
$ ssh -vv user@remote_host uptime OpenSSH_6.4, OpenSSL 1.0.1e-fips 11 Feb 2013 debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 51: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to remote_host [remote_host] port 22. debug1: Connection established. debug1: identity file /home/raven/.ssh/id_rsa type -1 debug1: identity file /home/raven/.ssh/id_rsa-cert type -1 debug1: identity file /home/raven/.ssh/id_dsa type -1 debug1: identity file /home/raven/.ssh/id_dsa-cert type -1 debug1: identity file /home/raven/.ssh/id_ecdsa type -1 debug1: identity file /home/raven/.ssh/id_ecdsa-cert type -1 debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_6.4 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9 debug1: match: OpenSSH_5.9 pat OpenSSH_5* debug2: fd 3 setting O_NONBLOCK debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug2: kex_parse_kexinit: ---- snipped - lots of kexinit messages ---- debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: mac_setup: found hmac-md5 debug1: kex: server->client aes128-cbc hmac-md5 none debug2: mac_setup: found hmac-md5 debug1: kex: client->server aes128-cbc hmac-md5 none debug1: sending SSH2_MSG_KEX_ECDH_INIT debug1: expecting SSH2_MSG_KEX_ECDH_REPLY debug1: Server host key: RSA 6c:4c:41:a3:d2:04:66:a1:e8:66:2d:35:4c:79:6a:98 debug1: Host 'remote_host' is known and matches the RSA host key. debug1: Found key in /home/raven/.ssh/known_hosts:4 debug1: ssh_rsa_verify: signature correct debug2: kex_derive_keys debug2: set_newkeys: mode 1 debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug2: set_newkeys: mode 0 debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug2: key: /home/raven/.ssh/id_rsa ((nil)), debug2: key: /home/raven/.ssh/id_dsa ((nil)), debug2: key: /home/raven/.ssh/id_ecdsa ((nil)), debug1: Authentications that can continue: publickey,password,keyboard-interactive debug1: Next authentication method: publickey debug1: Trying private key: /home/raven/.ssh/id_rsa debug1: Trying private key: /home/raven/.ssh/id_dsa debug1: Trying private key: /home/raven/.ssh/id_ecdsa debug2: we did not send a packet, disable method debug1: Next authentication method: keyboard-interactive debug2: userauth_kbdint debug2: we sent a keyboard-interactive packet, wait for reply debug2: input_userauth_info_req debug2: input_userauth_info_req: num_prompts 1 Password: debug2: input_userauth_info_req debug2: input_userauth_info_req: num_prompts 0 debug1: Authentication succeeded (keyboard-interactive). Authenticated to remote_host ([remote_host]:22). debug1: channel 0: new [client-session] debug2: channel 0: send open debug1: Requesting firstname.lastname@example.org debug1: Entering interactive session. debug2: callback start debug2: fd 3 setting TCP_NODELAY debug2: client_session2_setup: id 0 debug1: Sending environment. debug1: Sending env LANG = en_GB.UTF-8 debug2: channel 0: request env confirm 0 debug1: Sending command: uptime debug2: channel 0: request exec confirm 1 debug2: callback done debug2: channel 0: open confirm rwindow 0 rmax 32768 debug2: channel 0: rcvd adjust 2097152 debug2: channel_input_status_confirm: type 99 id 0 debug2: exec request accepted on channel 0 debug1: client_input_channel_req: channel 0 rtype exit-status reply 0 debug1: client_input_channel_req: channel 0 rtype email@example.com reply 0 debug2: channel 0: rcvd eow debug2: channel 0: close_read debug2: channel 0: input open -> closed debug2: channel 0: rcvd eof debug2: channel 0: output open -> drain debug2: channel 0: obuf empty debug2: channel 0: close_write debug2: channel 0: output drain -> closed debug2: channel 0: rcvd close debug2: channel 0: almost dead debug2: channel 0: gc: notify user debug2: channel 0: gc: user detached debug2: channel 0: send close debug2: channel 0: is dead debug2: channel 0: garbage collecting debug1: channel 0: free: client-session, nchannels 1 Transferred: sent 2472, received 1816 bytes, in 0.8 seconds Bytes per second: sent 3032.4, received 2227.7 debug1: Exit status 0