How to wire linux shell (sh) script to test with ping if host is reachable?
I guess there could be solution that uses grep but maybe ping provides that option by itself?
I am more into getting a whitelisting a successful ping operation that reached the host then checking if there was any error. I don't care about the reason of ping not succeeding in reaching a host.
I would like to limit ping attempts count and maximum amount of time to reach the host so the script does not waits too long for ping trying to reach a host.
dt=$(date +%d)
cksize=50
echo "Start $(date)"
while IFS= read -r sn
do
echo "*************************************************"
echo "Begin checking NODES client: $sn"
if ping -c 1 "$sn" -i 5 > /dev/null
then
echo "$sn node up"
else
echo "$sn node down"
fi
done < server_list
parallel -j0 --timeout 15 'ping -c 5 -i 0.2 {} >/dev/null 2>&1 && echo {} up || echo {} down' ::: freenetproject.org debian.org no-such.domain {1..254}.2.3.4
You can do it like this. It will do it in parallel for all hosts.
#!/bin/bash
for server in 'google.com' 'github.com' 'fakeserver.com'
do
{ ping -o "$server" &>/dev/null && echo "$server is UP" || echo "$server is DOWN" ; } &
done
wait
Regards!
Related
Im trying to wait for a device to boot up in my code and i dont want to use sleep to wait for him.
my problem is that sometimes the device fail to boot and im stuck in a loop when using:
until ping -c1 www.google.com &>/dev/null; do :; done
while true; do ping -c1 www.google.com > /dev/null && break; done
How can i try to ping to the device for X seconds and print "DEAD" or "ALIVE" using one liner?
You can use this linux utility: https://linux.die.net/man/1/timeout
And your oneliner would be something like this:
timeout 50 bash -c "while true; do if ping -c1 -i1 8.8.8.8 &>/dev/null; then echo "up"; break; fi; done"
You need -W option that keeps ping waiting for a timeout of X seconds.
For Linux (iputils):
$ ping -c1 -W10 <url>
For MacOS X:
$ ping -c1 -t10 <url>
Not a one-liner, but this would wait for 10 seconds before timing out:
if ping -c 1 -W 10 www.google.com 1>/dev/null; then
echo Success;
else
echo Failed;
fi
RHEL 7.1 is the OS this will be used on.
I have two servers which are identical (A and B). Server B needs to monitor a port on Server A and if it's down for 30 seconds, launch a script. I read netcat was replaced with ncat on RHEL 7 so this is what I have so far:
#!/bin/bash
Server=10.0.0.1
Port=123
ncat $Server $Port &> /dev/null; echo $?
If the port is up, the output is 0. If the port is down, the output is 1. I'm just not sure on how to do the next part which would be "if down for 30 seconds, then launch x script"
Any help would be appreciated. Thanks in advance.
If you really want to script this rather than using a dedicated tool like Pacemaker as #CharlesDuffy suggested, then you could do something like this:
Run an infinite loop
Check the port
If up, save the timestamp
Otherwise check the difference from the last saved timestamp
If more time passed then threshold, then run the script
Sleep a bit
For example:
#!/bin/bash
server=10.0.0.1
port=123
seconds=30
seen=$(date +%s)
while :; do
now=$(date +%s)
if ncat $server $port &> /dev/null; then
seen=$now
else
if ((now - seen > seconds)); then
run-script && exit
fi
fi
sleep 1
done
#!/bin/bash
Server=10.0.0.1
Port=123
port_was_down=0
while true; do
sleep 30
if ! ncat $Server $Port &> /dev/null; then
if [[ $port_was_down == "1" ]]; then
run-script
exit
else
port_was_down=1
fi
else
port_was_down=0
fi
done
what about using nmap?
something like:
TIMEOUT=30s;
HOST=10.0.0.1;
PORT=123;
if nmap --max-rtt-timeout $TIMEOUT --min-rtt-timeout $TIMEOUT -p $PORT $HOST | grep "^$PORT.*open"; then
echo 'OPEN';
else
echo 'CLOSED';
fi;
ip="192.168.129."
function addToList(){
list="$list $1"
}
addToList $1
for i in $ip{$list}
do
ping -c 1 $ip$1 > /dev/null
echo "Ping Status of $ip$1 : Success" ||
echo "Ping Status of $ip$1 : Failed"
done
How can i ping more than one host at the same time and show it in a list which ip address is up or down?
One way is to use a more powerful ping tool like fping.
The other approach is to run the pings in the background:
for ip in $*; do
if [[ "$ip" =~ "^[0-9]+$" ]]; then
ip="192.168.129.$ip"
fi
(
ping -c 1 $ip > /dev/null
if [ $? -eq 0 ]; then
echo "node $ip is up"
else
echo "node $ip is down"
fi
)&
done
(...)& runs a script in the background.
Here is a script I wrote after reading a similar post.
https://bitbucket.org/kurtjensen/nettest/src/master/
It can use multiple text files as possible configs and the config files give you a chance to name the ip address more descriptively. The example config files are
home.txt - Which is the default
momdad.txt - This is for my parents network
etc.
So I can run the script at home and just hit enter at the prompt or enter something like "momdad" to switch to a different config fo a different network.
I am a beginner user of linux, and also quite newbie at ssh and tunnels.
Anyway, my goal is to maintain a ssh tunnel open in background.
In order to do that, I wrote the following batch that I then added into crontab (the batch is automatically processed every 5 minutes during workdays and from 8am to 9pm).
I read in some other thread in stackoverflow that one should use autossh that will ensure the ssh will always be ok through a recurrent check. So did I....
#!/bin/bash
LOGFILE="/root/Tunnel/logBatchRestart.log"
NOW="$(date +%d/%m/%Y' - '%H:%M)" # date & time of log
if ! ps ax | grep ssh | grep tunnelToto &> /dev/null
then
echo "[$NOW] ssh tunnel not running : restarting it" >> $LOGFILE
autossh -f -N -L pppp:tunnelToto:nnnnn nom-prenom#193.xxx.yyy.zzz -p qqqq
if ! ps ax | grep ssh | grep toto &> /dev/null
then
echo "[$NOW] failed starting tunnel" >> $LOGFILE
else
echo "[$NOW] restart successfull" >> $LOGFILE
fi
fi
My problem is that sometimes the tunnel stops working, although every thing looks ok (ps ax | grep ssh > the result shows the two expected tasks : autossh main task and the ssh tunnel itself). I actually know about the problem cause the tunnel is used by a third party software that triggers an error as soon as the tunnel is no more responding.
SO I am wondering how I should improve my batch in order It will be able to check the tunnel and restart it if it happens to be dead. I saw some ideas in there, but it was concluded by the "autossh" hint... which I already use. Thus, I am out of ideas... If any of you have, I'd gladly have a look at them!
Thanks for taking interest in my question, and for your (maybe) suggestions!
Instead of checking the ssh process with ps you can do the following trick
create script, that does the following and add it to your crontab via crontab -e
#!/bin/sh
REMOTEUSER=username
REMOTEHOST=remotehost
SSH_REMOTEPORT=22
SSH_LOCALPORT=10022
TUNNEL_REMOTEPORT=8080
TUNNEL_LOCALPORT=8080
createTunnel() {
/usr/bin/ssh -f -N -L$SSH_LOCALPORT:$REMOTEHOST:SSH_REMOTEPORT -L$TUNNEL_LOCALPORT:$REMOTEHOST:TUNNEL_REMOTEPORT $REMOTEUSER#$REMOTEHOST
if [[ $? -eq 0 ]]; then
echo Tunnel to $REMOTEHOST created successfully
else
echo An error occurred creating a tunnel to $REMOTEHOST RC was $?
fi
}
## Run the 'ls' command remotely. If it returns non-zero, then create a new connection
/usr/bin/ssh -p $SSH_LOCALPORT $REMOTEUSER#localhost ls >/dev/null 2>&1
if [[ $? -ne 0 ]]; then
echo Creating new tunnel connection
createTunnel
fi
In fact, this script will open two ports
port 22 which will be used to check if the tunnel is still alive
port 8080 which is the port you might want to use
Please check and send me further questions via comments
(I add this as an answer since there is not enough room for it un a comment)
Ok, I managed to make the batch run to launch the ssh tunnel (I had to specify my hostname instead of localhost in order it could be triggered) :
#!/bin/bash
LOGFILE="/root/Tunnel/logBatchRedemarrage.log"
NOW="$(date +%d/%m/%Y' - '%H:%M)" # date et heure du log
REMOTEUSER=username
REMOTEHOST=remoteHost
SSH_REMOTEPORT=22
SSH_LOCALPORT=10022
TUNNEL_REMOTEPORT=12081
TUNNEL_SPECIFIC_REMOTE_PORT=22223
TUNNEL_LOCALPORT=8082
createTunnel() {
/usr/bin/ssh -f -N -L$SSH_LOCALPORT:$REMOTEHOST:$SSH_REMOTEPORT -L$TUNNEL_LOCALPORT:$REMOTEHOST:$TUNNEL_REMOTEPORT $REMOTEUSER#193.abc.def.ghi -p $TUNNEL_SPECIFIC_REMOTE_PORT
if [[ $? -eq 0 ]]; then
echo [$NOW] Tunnel to $REMOTEHOST created successfully >> $LOGFILE
else
echo [$NOW] An error occurred creating a tunnel to $REMOTEHOST RC was $? >> $LOGFILE
fi
}
## Run the 'ls' command remotely. If it returns non-zero, then create a new connection
/usr/bin/ssh -p $SSH_LOCALPORT $REMOTEUSER#193.abc.def.ghi ls >/dev/null 2>&1
if [[ $? -ne 0 ]]; then
echo [$NOW] Creating new tunnel connection >> $LOGFILE
createTunnel
fi
However, I got some immediate message (below) when the tunnel is running and when cron tries to lauch the batch again... sounds like it cannot listen to it. Also since I need some time to get a proof , I can't say yet it will successfully restart if the tunnel is out.
Here's the response to the second start of the batch.
bind: Address already in use channel_setup_fwd_listener: cannot listen
to port: 10022 bind: Address already in use
channel_setup_fwd_listener: cannot listen to port: 8082 Could not
request local forwarding.
Every night I go through the same process of checking failover systems for our T1's. I essentially go through the following process:
Start the failover process.
traceroute $server;
Once I see it's failed over, I verify that connections work by SSHing into a server.
ssh $server;
Then once I see it works, I take it off of failover.
So what I want to do is to continually run a traceroute until I get a certain result, then run a SSH command.
Put your list of successful messages in a file (omit the variable lines and fractions of the line, and use a ^ to identify the start of the line, as such:)
patterns.list:
^ 7 4.68.63.165
^ 8 4.68.17.133
^ 9 4.79.168.210
^10 216.239.48.108
^11 66.249.94.46
^12 72.14.204.99
Then a simple while loop:
while ! traceroute -n ${TARGET} | grep -f patterns.list
do
sleep 5 # 5 second delay between traceroutes, for niceness.
done
ssh ${DESTINATION}
Use traceroute -n to generate the output so you don't get an IP address that resolves one time, but and a name the next, resulting in a false positive.
I think you could be better off using ping command to verify server's accessability than traceroute.
It is easy to check for return status of ping command without using any grep at all:
if [ ping -c 4 -n -q 10.10.10.10 >/dev/null 2>& ]; then
echo "Server is ok"
else
echo "Server is down"
fi
If you want to do it continually in a loop, try this:
function check_ssh {
# do your ssh stuff here
echo "performing ssh test"
}
while : ; do
if [ ping -c 4 -n -q 10.10.10.10 >/dev/null 2>& ]; then
echo "Server is ok"
check_ssh
else
echo "Server is down"
fi
sleep 60
done