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While loop stops reading after the first line in Bash
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My script is working fine butit is not taking next server from the server list
#!/bin/bash
# Read in server names from afile
while read -r server; do
# Check if server is reachable
if ping -c 1 "$server" &> /dev/nul l; then
echo "Server $server is reachable."
# Check if mount point exists
if ssh "$server" "[ -d /path/to/mount/point ]"; then
echo "Mount point exists on server $server."
else
echo "Mount point does not exist on server $server."
fi
else
echo "Server $server is not reachable."
fi
done < servers.txt
For an example 192.168.0.1 and 192.168.0.2 is there in server list file .but it is showing output for 192.168.0.1 . It is not showing output for 192.168.0.2
As pointed out in the comments section, ssh command is consuming your script stdin.
Add -n option to ssh should prevent this (see this).
So change this line:
if ssh "$server" "[ -d /path/to/mount/point ]"; then
To:
if ssh -n "$server" "[ -d /path/to/mount/point ]"; then
Related
This question already has answers here:
How to create a bash script to check the SSH connection?
(14 answers)
Closed 1 year ago.
I am writing a bash script that goes through a number of hosts defined in hosts.list and returns if they are online.
I would like to do the same but with ssh. How to I return a value from ssh like boolean if the connection and login was successful.
#!/bin/bash
File="hosts.list"
Hosts=$(cat $File)
declare -i deadhosts
$deadhosts = 0
declare -i counter
$counter = 0
for Host in $Hosts
do
if ! ping -c 1 -s 1 -W 1 "$Host" 1>/dev/null 2>&1; then
deadhosts=$((deadhosts+1))
else
echo $Host
fi
counter=$((counter+1))
done
echo "Mission success"
echo "Scanned Hosts: $counter Dead Hosts: $deadhosts"
There is a question that was ask for the same thing:
How to create a bash script to check the SSH connection?
And you can also find information there:
https://www.golinuxcloud.com/test-ssh-connection/
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Closed 4 years ago.
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I need to send mail to a particular user from host computer via shell script using command line argument.Mail should go to that particular user only.
Script execution will be like ./tesh.sh user emailid
cat test.sh
#!/bin/sh
export user=$1
export email=$2
list=`echo "$(cat ip.txt)"`
script=$(cat remote_cmds.sh)
for ip in ${list[#]} ; do
echo "***";
echo "IP: $ip"
ssh -o StrictHostKeyChecking=no -l ${user} ${ip} ${script}
done
# cat remote_cmds.sh
source pathto/test.sh
echo "";
echo "****Hostname****";
echo "`hostname`";
echo "";
echo "****Disk Allocated****";
echo "`df -h`";
echo "";
echo "****Ram Allocated****";
echo testmail | mailx -s "Testmail" $email
If I understand you correctly you have N computers with ip addresses saved in ip.txt. Each of these computers has a user named 'user' to which you can login via ssh. Each of these computers has a user named 'emailid' to which you want to send mail. You want to use ssh session to connect to these computers and run mail client on these computers. You want to print some information about hostname, disc space and some other infos from the remote computers on your computer and send simple mail with subject 'Testmail' and content 'testmail' to the local user 'emaillid' on these remote N computers.
These scripts are not good. Doing script=$(cat remote_cmds.sh) and then calling ssh ... ${scripts} is so dangerous... The line list=echo "$(cat ip.txt)" can be just shortened to list=$(cat ip.txt). list variable is not an array, so doing ${list[#]} is the same as $list. remote_cmds.sh has the line source pathto/test.sh, so that means that each of N computers has a test.sh file in the same path?
mailx is giving you arror, cause you are executing (literally) mailx -s Testmail $email and email address can't have $ characters (the email variable is not expanded).
Try smth like this:
test.sh
#!/bin/sh
# export is not needed anywhere here
user=$1
email=$2
# loop through the lines in ip.txt
cat ip.txt | while read ip; do
echo "***";
echo "IP: $ip"
# https://unix.stackexchange.com/questions/87405/how-can-i-execute-local-script-on-remote-machine-and-include-arguments
# login on computer with ip $ip on user $user and execute command on
# remote host 'bash -s', which will read commands from standard input,
# append our remote_cmds.sh script to stdin and pass "$email" as first
# argument to this script
ssh -o StrictHostKeyChecking=no -l "$user" "$ip" bash -c -- < remote_cmds.sh "$email"
done
# this loop is bad and inefficient, but it's safe and simple to write
# see https://stackoverflow.com/questions/1521462/looping-through-the-content-of-a-file-in-bash
remote_cmds.sh
#!/bin/sh
# these lines will be executed on N computers
# email is passed as first argument to this script
email=$1
echo "";
echo "****Hostname****";
hostname
echo "";
echo "****Disk Allocated****";
df -h
echo "";
echo "****Ram Allocated****";
free -h # ;)
echo testmail | mailx -s "Testmail" "$email"
I am using a for loop to connect to a list of servers and perform some simple commands. If the server is not accessible then stderr is written to a file. I then grep that file for the server name. It seems relatively simple and for some reason it isn't working. For troubleshooting purposes I have narrowed my server list to two servers and only run simple commands.
for i in $(cat serverlist)
do
nexec -i $i hostname 2>>errorlog.txt
if grep -q $i errorlog.txt; then echo "error accessing" $i
else echo "was able to connect to" $i
fi
done
So in the serverlist I have defined two incorrect hosts for troubleshooting purposes. Nexec tries to connect to each and perform the hostname command. If it is unable to connect an error message is printed to errorlog.txt
e.g.,
nexec: Error accessing host test1
Since both servers are incorrectly specified I am not able to connect to either. Again for troubleshooting purposes.
When grep runs the first time against $i which is the first server in the list it doen't find any matches in error.txt. However, it should. If I cat the results instead of grepping it is there.
I am actually doing this in bladelogic so the rules are a bit different. It should still work.
while read -r i <&3; do
nexec -i "$i" hostname 2>>"errorlog.$i.txt" || {
echo "nexec for $i exited with status $?" >&2
continue
}
# check for case where it claimed success but actually failed
# if nexec is written correctly, you don't need any of this logic
# ...and can completely remove the rest of the loop.
if grep -q -e "$i" "errorlog.$i.txt"; then
echo "error accessing $i" >&2
else
echo "was able to connect to $i" >&2
fi
done 3<serverlist
# and combine all the individual logs into one file:
cat errorlog.*.txt >errorlog.txt && rm -f -- errorlog.*.txt
Not familiar with nexec, but I imagine something like this is what you are looking for
for i in $(cat serverlist)
do
if [ ! "$(nexec -i $i hostname)" ]
then echo "error accessing" $i
else echo "was able to connect to" $i
fi
done
I am a beginner user of linux, and also quite newbie at ssh and tunnels.
Anyway, my goal is to maintain a ssh tunnel open in background.
In order to do that, I wrote the following batch that I then added into crontab (the batch is automatically processed every 5 minutes during workdays and from 8am to 9pm).
I read in some other thread in stackoverflow that one should use autossh that will ensure the ssh will always be ok through a recurrent check. So did I....
#!/bin/bash
LOGFILE="/root/Tunnel/logBatchRestart.log"
NOW="$(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