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Top Forums Shell Programming and Scripting Linux: Writing a tricky script to check connectivity Post 302284991 by fimblo on Friday 6th of February 2009 05:58:30 PM
Old 02-06-2009
I had some similar code at home, heres a slightly modified version for you.

Note that there are two reset functions included, depending on if you will ssh or telnet. And you'll prolly need to read a few man-pages to get things right.

---------------------------------------
#!/usr/bin/env bash

MY_MODEM_IP=123.12.1.1
HOST_TO_CHECK=www.comcast.net
SOME_TIME=$(( 5 * 60 )) # seconds

ping_fails () {
# check your ping manpage for flags so that it
# o sends one ping then quits
# o waits only a second or so for the pong
! ping -XXX $HOST_TO_CHECK > /dev/null 2>&1
}

reset_modem_ssh () {
# Make sure you've made a public and private key if you're going
# with ssh.
{
echo 'reset';
} | ssh $MY_MODEM_IP
}

reset_modem_telnet () {
# If you go with telnet, dont forget to echo your password. I've
# noticed that some applications are a little slow, adding sleeps
# is a simple workaround.
{
sleep 0.2
echo "yourpassword"
sleep 0.2
echo "reset"
} | telnet $MY_MODEM_IP
}


while sleep $SOME_TIME ; do
ping_fails && reset_modem_ssh
done

------------------------------------
And to be on the safe side, specify the ping host with its ip address, not its hostname.
 

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SSH-KEYSIGN(8)						    BSD System Manager's Manual 					    SSH-KEYSIGN(8)

NAME
ssh-keysign -- ssh helper program for host-based authentication SYNOPSIS
ssh-keysign DESCRIPTION
ssh-keysign is used by ssh(1) to access the local host keys and generate the digital signature required during host-based authentication with SSH protocol version 2. ssh-keysign is disabled by default and can only be enabled in the global client configuration file /etc/ssh/ssh_config by setting EnableSSHKeysign to ``yes''. ssh-keysign is not intended to be invoked by the user, but from ssh(1). See ssh(1) and sshd(8) for more information about host-based authen- tication. FILES
/etc/ssh/ssh_config Controls whether ssh-keysign is enabled. /etc/ssh/ssh_host_dsa_key /etc/ssh/ssh_host_ecdsa_key /etc/ssh/ssh_host_ed25519_key /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys used to generate the digital signature. They should be owned by root, read- able only by root, and not accessible to others. Since they are readable only by root, ssh-keysign must be set-uid root if host- based authentication is used. /etc/ssh/ssh_host_dsa_key-cert.pub /etc/ssh/ssh_host_ecdsa_key-cert.pub /etc/ssh/ssh_host_ed25519_key-cert.pub /etc/ssh/ssh_host_rsa_key-cert.pub If these files exist they are assumed to contain public certificate information corresponding with the private keys above. SEE ALSO
ssh(1), ssh-keygen(1), ssh_config(5), sshd(8) HISTORY
ssh-keysign first appeared in OpenBSD 3.2. AUTHORS
Markus Friedl <markus@openbsd.org> BSD
December 7, 2013 BSD
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