Impossible to get output of remote ssh commands via cron

[Iván_García_Díe]

Hello,

I have made a bash script to get ipstats of several devices, and i have a problem with my X450a-48t, the script works fine if i execute it manually, but in crontab no output, i think because in cron no tty is allocated.

Example script:

#!/bin/bash

ssh -o "StrictHostKeyChecking no" admin@10.26.196.189 "show ipstats"

i have checked ssh with -t and -tt option, but doesn't work.

¿Any idea how to solve it? ¿another possibility to get this stats remotely?

Regards,

Ivan

[Erik_Auerswald]

Hm, I have just tested this with an X460-G2, EXOS 21.1.1.4, OpenSSH_6.6.1p1, and ISC cron 3.0pl1-124ubuntu2 on Ubuntu 14.04. The original command works fine, both from the command line and from cron (crontab of an unprivileged user). I have tested both from inside a BASH script and the ssh command directly in the crontab entry. No "-t" options needed.

[Erik_Auerswald]

Hi,

the script started by cron probably has no SSH agent available. You could try to specify the identity (key) file to use with the option -i.
ssh -i /path/to/key_file -o "StrictHostKeyChecking no" admin@10.26.196.189 "show ipstats"Regards,
Erik

[Erik_Auerswald]

Hello Ivan,

did you try to use two -t options?
ssh -o "StrictHostKeyChecking no" -t -t admin@10.26.196.189 "show ipstats"As I understand it more than one -t option is needed to really force pseudo-tty allocation.

Erik

Edit: Just re-read your first post, you wrote that you already tried -tt...

[Iván_García_Díe]

Hi Erik,

No difference with -i option. There is no problem with authentication. I share debug output, you can see "Authentication succeeded". The problem i think is this line "debug2: channel 0: read failed"

OpenSSH_5.1p1, OpenSSL 0.9.8j-fips 07 Jan 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to 10.26.196.189 [10.26.196.189] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug2: key_type_from_name: unknown key type '-----END'
debug1: identity file /root/.ssh/id_rsa type 1
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug2: key_type_from_name: unknown key type '-----END'
debug1: identity file /root/.ssh/id_dsa type 2
debug1: Remote protocol version 2.0, remote software version 4.1.2 SSH Secure Shell Toolkit
debug1: no match: 4.1.2 SSH Secure Shell Toolkit
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.1
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes256-ctr,arcfour256,arcfour,aes128-cbc,aes256-cbc
debug2: kex_parse_kexinit: aes128-ctr,aes256-ctr,arcfour256,arcfour,aes128-cbc,aes256-cbc
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-dss
debug2: kex_parse_kexinit: aes256-cbc,aes192-cbc,aes128-cbc,twofish256-cbc,twofish-cbc,twofish192-cbc,twofish128-cbc,blowfish-cbc,3des-cbc
debug2: kex_parse_kexinit: aes256-cbc,aes192-cbc,aes128-cbc,twofish256-cbc,twofish-cbc,twofish192-cbc,twofish128-cbc,blowfish-cbc,3des-cbc
debug2: kex_parse_kexinit: hmac-sha1,hmac-md5,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-sha1,hmac-md5,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none
debug2: kex_parse_kexinit: none
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
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
debug2: dh_gen_key: priv key bits set: 123/256
debug2: bits set: 494/1024
debug1: sending SSH2_MSG_KEXDH_INIT
debug1: expecting SSH2_MSG_KEXDH_REPLY
debug1: Host '10.26.196.189' is known and matches the DSA host key.
debug1: Found key in /root/.ssh/known_hosts:4
debug2: bits set: 525/1024
debug1: ssh_dss_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: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /root/.ssh/id_rsa (0x7f2e3b150be0)
debug2: key: /root/.ssh/id_dsa (0x7f2e3b150b30)
debug1: Authentications that can continue: publickey,keyboard-interactive,password
debug1: Next authentication method: publickey
debug1: Offering public key: /root/.ssh/id_rsa
debug2: we sent a publickey packet, wait for reply
debug1: Server accepts key: pkalg ssh-rsa blen 277
debug2: input_userauth_pk_ok: fp 2a:f5:57:63:32:81:62:57:31:e9:de:46:7e:49:eb:ca
debug1: read PEM private key done: type RSA
debug1: Authentication succeeded (publickey).
debug2: fd 4 setting O_NONBLOCK
debug2: fd 5 setting O_NONBLOCK
debug2: fd 6 setting O_NONBLOCK
debug1: channel 0: new [client-session]
debug2: channel 0: send open
debug1: Entering interactive session.
debug2: callback start
debug2: client_session2_setup: id 0
debug1: Sending environment.
debug1: Sending command: show ipstats
debug2: channel 0: request exec confirm 1
debug2: fd 3 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 16384 rmax 32768
debug2: channel 0: read<=0 rfd 4 len 0
debug2: channel 0: read failed
debug2: channel 0: close_read
debug2: channel 0: input open -> drain
debug2: channel 0: ibuf empty
debug2: channel 0: send eof
debug2: channel 0: input drain -> closed
debug2: channel_input_confirm: type 99 id 0
debug2: exec request accepted on channel 0
debug2: channel 0: rcvd eof
debug2: channel 0: output open -> drain
debug2: channel 0: rcvd close
debug2: channel 0: obuf empty
debug2: channel 0: close_write
debug2: channel 0: output drain -> closed
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
debug1: fd 0 clearing O_NONBLOCK
debug1: fd 1 clearing O_NONBLOCK
debug1: fd 2 clearing O_NONBLOCK
Transferred: sent 1960, received 2008 bytes, in 0.1 seconds
Bytes per second: sent 21000.3, received 21514.6
debug1: Exit status -1