I'm trying to automate the startup (after reboot) of an application that runs on a grid of 12 Linux 7 servers.
The 12 servers get rebooted in random order.
All the servers need to be running before I can start up the application that resides on the 12 servers.
What I'd like to do is to test that all 12 Linux 7 servers are up and then when all 12 are up, I'd proceed with the startup sequence of commands.
All 12 server are set up with ssh keys.
cat serverlist.txt
10.0.0.6
10.0.0.7
10.0.0.8
10.0.0.9
...
10.0.0.18
I want to ping a server and then wait until the ping is successful, then move to the next IP address.
My apologies for my question.
How to code this?
Read in the first line from IP list file.
Ping first IP until success, then ping the other IP addresses (one at a time) until the success of all 12.
Then, run commands to start the application on the grid of 12 servers.
Question: How to code this in the bash shell.
The inner loop can be as simple as
while ! ssh "${connection_string}" -o ConnectTimeout=5 true
do
sleep 0.5
done
This runs a trivial command, and waits for 0.5 seconds between retries.
for i in `cat /home/Startup/serverlist.txt`
do
ssh ${i} -o ConnectTimeout=5 true
while test $? -gt 0
do
ssh ${i} -o ConnectTimeout=5 true
done
done
exit
If ssh works the server is alive, plus the use of the timeout is a better way to speed up the script execution. If the script get finish that means all the servers are up and responding.
Related
My intention is to cycle through my list of ips and poweroff if my ping succeeds first. However the systems seems to hang. After running this script I can't ping the systems anymore and they aren't powered off. If I run ssh 192.168.1.ip "sudo poweroff" through terminal I dont encounter this issue. Any advice?
for ((ip=40, cnt=0; ip<=max; ip++, cnt++))
do
if ping -c 1 192.168.1.$ip &> /dev/null
then
printf "\n${array[$cnt]}: Ping Successful"
ssh 192.168.1.$ip "sudo poweroff"
printf "\n${array[$cnt]}: Power Down Executed\n"
sleep 1
else
printf "\n${array[$cnt]}: Ping Failed\n"
fi
done
After running a single ssh 192.168.1.40 "sudo poweroff" the system is properly powered off. When running my script, I am unable to ping the systems however I can visually see the fans and leds are still on. I think I should use a KVM to take a closer look since ssh doesn't allow allow connection after this script is run. Still at first glance I dont understand how running ssh 192.168.1.40 "sudo poweroff" and running it through my script really makes a difference. Anyways I'll try to add more information tomorrow.
ssh 192.168.1.$ip "(sleep 5; sudo poweroff)&" to put the process in the background on the remote host and sleep for 5 seconds before powering off to give time for the script to complete and exit the remote host before it goes down... – David C. Rankin
This Resolved my Issue.
I'm trying to get a script to run at startup, but does nothing if I've connected to my Raspberry Pi via SSH.
So far I've got the crontab to automatically run the script checkssh.sh via #reboot sleep 30 && sudo bash ./checkssh.sh and './checkssh.sh' contains this:
#!/bin/bash
if [ -n "$SSH_CLIENT" ] || [ -n "$SSH_TTY" ]; then
echo "SSH CONNECTED"
else
./autobackup.sh
fi
Running checkssh.sh from an SSH terminal returns 'SSH CONNECTED' which is expected, and letting it run automatically from the crontab at reboot when SSH isn't connected works correctly. However, when it runs at boot and I connect via SSH as soon as it's available, it still runs the script. I'm not sure where this is going wrong.
I need it to run automatically and if there's no SSH connection run autobackup.sh , but if there is an SSH connection, not to run anything. The device I use for the SSH connection may vary & the network used may also vary, so a script that relies on specific IP's isn't ideal.
Thanks for any help :)
Those environment variables (SSH_CLIENT and SSH_TTY) are only set in the environment of an SSH session. You cannot check them from another process and expect them to fulfill your goals here.
Instead, run the program finger. This is the standard way to see who is logged in.
Probably you need to add some delay before running your script to allow for the SSH service to come up. If cron service comes up before the sshd does, you will have a failure. Try:
#reboot sleep 60 && bash ./checkssh.sh
Also I would substitute the '.' with the full script path.In one scenario I had to add as many as 120 seconds to get the #reboot crontab to work right. But ssh should not need as much. I guess you can trim 60 seconds according to your needs after you get it working.
I've set up a simple init.d script "S3logrotate" to run on shutdown. The "S3logrotate" script works fine when run manually from command line but the script does not function correctly on shut down.
The script uploads logs from my PC to an Amazon S3 bucket and requires wifi to run correctly.
Debugging proved that the script is actually run but the upload process fails.
I found that the problem seems to be that the script seems to run after wifi is terminated.
These are the blocks I used to test my internet connection in the script.
if ping -q -c 1 -W 1 8.8.8.8 >/dev/null; then
echo "IPv4 is up" >> *x.txt*
else
echo "IPv4 is down" >> *x.txt*
fi
if ping -q -c 1 -W 1 google.com >/dev/null; then
echo "The network is up" >> *x.txt*
else
echo "The network is down" >> *x.txt*
fi
The output for this block is:
IPv4 is down
The network is down
Is there any way to set the priority of an init.d script? As in, can I make my script run before the network connection is terminated? If not, is there any alternative to init.d?
I use Ubuntu 16.04 and have dual booted with Windows 10 if that's significant.
Thanks,
sganesan7
You should place you scrip in:
/etc/NetworkManager/dispatcher.d/pre-down.d
change group and owner to root
chown root:root S3logrotate
and it should work. If you need to do this for separate interface place script in
create a script inside
/etc/NetworkManager/dispatcher.d/
and name it (for example):
wlan0-down
and should work too.
I don't have a powerful hardware so I can't run multiple ssh tunnels at the same time or it'll make the CPU load go way too high, my goal is to run a ssh tunnel after another one is connected, and reconnect if one of my ssh gets disconnected, so basically it's like this:
while true; do
if (1st ssh isn't connected); then
connect the first ssh
elif (1st ssh is finally connected); then
run the second ssh
elif (2nd ssh is finally connected); then
run the 3rd ssh
fi
sleep 1
done
The problem is that the amount of ssh tunnels keeps changing, sometimes a user wants to run 3 ssh tunnels and sometimes 5, it looks like this to run the script:
mytunnel.sh -a [number of tunnels they wanna run]
I'm thinking of for loop but I just can't figure out how to write it inside a for loop. Please help me.
Here is a for loop you can use:
#!/usr/local/bin/bash
LOOP=$1
for (( c=1; c<=$LOOP; c++ ))
do
echo "$c "
done
Replace echo with your commands and LOOP with whatever command-line arg you'll be using. This example reads command-line arg 1 (i.e. $1).
Example execution:
Tricky. Unfortunately I don't think ssh returns anything when it connects a tunnel, nor does it exit immediately when the connection is broken.
Instead what you probably want to do is make a port monitor that periodically checks that the port is accepting connections and spawns a new ssh tunnel (possibly killing the old ssh process) if it isn't.
I am an R user. I always run programs on multiple computers of campus. For example, I need to run 10 different programs. I need to open PuTTY 10 times to log into the 10 different computers. And submit each of programs to each of 10 computers (their OS is Linux). Is there a way to log in 10 different computers and send them command at same time? I use following command to submit program
nohup Rscript L_1_cc.R > L_1_sh.txt
nohup Rscript L_2_cc.R > L_2_sh.txt
nohup Rscript L_3_cc.R > L_3_sh.txt
First set up ssh so that you can login without entering a password (google for that if you don't know how). Then write a script to ssh to each remote host to run the command. Below is an example.
#!/bin/bash
host_list="host1 host2 host3 host4 host5 host6 host7 host8 host9 host10"
for h in $host_list
do
case $h in
host1)
ssh $h nohup Rscript L_1_cc.R > L_1_sh.txt
;;
host2)
ssh $h nohup Rscript L_2_cc.R > L_2_sh.txt
;;
esac
done
This is a very simplistic example. You can do much better than this (for example, you can put the ".R" and the ".txt" file names into a variable and use that rather than explicitly listing every option in the case).
Based on your topic tags I am assuming you are using ssh to log into the remote machines. Hopefully the machine you are using is *nix based so you can use the following script. If you are on Windows consider cygwin.
First, read this article to set up public key authentication on each remote target: http://www.cyberciti.biz/tips/ssh-public-key-based-authentication-how-to.html
This will prevent ssh from prompting you to input a password each time you log into every target. You can then script the command execution on each target with something like the following:
#!/bin/bash
#kill script if we throw an error code during execution
set -e
#define hosts
hosts=( 127.0.0.1 127.0.0.1 127.0.0.1)
#define associated user names for each host
users=( joe bob steve )
#counter to track iteration for correct user name
j=0
#iterate through each host and ssh into each with user#host combo
for i in ${hosts[*]}
do
#modify ssh command string as necessary to get your script to execute properly
#you could even add commands to transfer the file into which you seem to be dumping your results
ssh ${users[$j]}#$i 'nohup Rscript L_1_cc.R > L_1_sh.txt'
let "j=j+1"
done
#exit no error
exit 0
If you set up the public key authentication, you should just have to execute your script to make every remote host do their thing. You could even look into loading the users/hosts data from file to avoid having to hard code that information into the arrays.