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bash script to execute a command remote servers using ssh

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Top Forums Shell Programming and Scripting bash script to execute a command remote servers using ssh
# 1  
Old 04-03-2012
bash script to execute a command remote servers using ssh
Hello,

I am running into few issues, please suggest me what I am missing.

I am running this script on a linux host.

Main idea of this script is to, login to each host via ssh and get uid of user, service user that I trying to run this script, has already deployed ssh keys and provide sudo access to root with password less on all the server.

issue: /tmp/hostname.txt file contains list of IP addresses line by line, when I execute this script, I get the o/p of the first host successfully and stops executing right from that point.

Code:
# more userid
#!/bin/bash
while read line
do
        ssh $line '(echo "`hostname` UID for User v7866 is `getent passwd v7866 | cut -f3 -d:`")' >> /tmp/output
done < /tmp/hostname.txt
#
#more /tmp/hostname.txt
10.10.7.182
10.10.7.173
10.10.7.143
#

Thanks,
# 2  
Old 04-03-2012
ssh tries to read from the same standard input as your while loop, 'eating' your entire datafile.

Also, you don't need to re-open the same logfile 9,000 times to write 9,000 lines.

Also, the braces aren't necessary.

Code:
#!/bin/bash
while read line
do
        ssh $line 'echo "`hostname` UID for User v7866 is `getent passwd v7866 | cut -f3 -d:`"' </dev/null
done < /tmp/hostname.txt > /tmp/output

Last edited by Corona688; 04-04-2012 at 11:13 AM..
# 3  
Old 04-03-2012
A better way to accomplish this is to invoke the script which contains the commands that you want to be executed at the remote server
Code:
for ip_addr in $(cat hostname.txt); do
     ssh ${ip_addr} "bash -s" < script_to_be_invoked
done

As you'll see that, this way
Code:
ssh ip_addr "commands"

won't work properly while the "commands" is getting longer!
Look at this https://www.unix.com/shell-programmin...te-server.html
The reason why your commands will only be run on the first host connected to is detailed explained here
http://72.14.189.113/howto/shell/while-ssh/
Last edited by complex.invoke; 04-03-2012 at 11:31 PM..
This User Gave Thanks to complex.invoke For This Post:
bobby320
# 4  
Old 04-05-2012
Thanks for the help,

I was able to run the script as suggested works fine !!!!
Code:
for ip_addr in $(cat hostname.txt); do
     ssh ${ip_addr} "bash -s" < script_to_be_invoked
done

The only annoying part is, once the user ssh into the each server, I see banner is being displayed on the terminal, how do we remove that from the output.

Thanks,
# 5  
Old 04-06-2012
Quote:
Originally Posted by bobby320
The only annoying part is, once the user ssh into the each server, I see banner is being displayed on the terminal, how do we remove that from the output.

Thanks,
Just map the ip addresses of your remote servers' with a unique name one by one and line by line in your /etc/hosts on the master server which can manage all your remote servers
Code:
192.168.0.17 node0
192.168.0.18 node1
192.168.0.19 node2

A more convenient way to perform your tasks with ssh at the remote servers is to invoke another script ssh.sh
Code:
ssh ${0##*/} "${@}"

just locate the script ssh.sh in /usr/local/sbin, then make some soft links:
Code:
# cd /usr/local/sbin
# ln -s ssh.sh node0
# ln -s ssh.sh node1
# ln -s ssh.sh node2

after you have done this, you can login to remote server,say, login to node1, you can just execute
Code:
# node1

instead of
Code:
# ssh node1

or
Code:
# ssh 192.168.0.18

and the same way to execute your commands
Code:
# node1 "commands"

instead of
Code:
# ssh node1 "commands"

and so
Code:
for node in node1 node2 node3; do
     ${node} "bash -s" < script_to_be_invoked
done

The script below is detailed explained what you can do with no-ssh needed remote commands execution
Code:
#!/bin/bash
#
# ssh.sh
# node1 "echo '${local_variable}'"
# node1 "cat local_big_archive.tar.bz2" | tar -jxpvf -
# tar -jcpvf - /path/to/data | node1 "cat > /dev/tape"
# node1 "cd /path/to/dir; tar -jxpvf -" < local_big_archive.tar.bz2
# node1 "dd if=/dev/sda bs=512 count=1" | node2 "cd /usr; dd of=mbr.bin"
# node1 "dd <  /dev/sda bs=512 count=1" | node2 "cd /usr; dd >  mbr.bin"
# node1 "mysqldump" | mysql
# node1 "mysqldump" > backup.sql
# node1 
# node1 "uptime"
# node1 "uptime" > local_file  
# node1 "uptime  > remote_file"
# node1 "bash -s" < script_to_run
# node1 "bash -s" < script_to_run > local_file
# node1 "bash -s  > remote_file" < script_to_run
# tar -jcpvf - /path/to/data | node1 "cd /target/dir; tar -jxpvf -"
# cd /target/dir; node1 "tar -jcpvf - /path/to/data" |  tar -jxpvf -
# rsync -Pvzrtopg /path/to/data/ node1:/root/
# rsync -Pvzrtopg node1:/path/to/data /root/

ssh ${0##*/} "${@}"

Last edited by complex.invoke; 04-06-2012 at 12:32 PM..
# 6  
Old 04-10-2012
When I tried to include sudo command in the place script to be executed I am getting this error messages, any idea how can I overcome !!!!
Code:
#!/bin/bash
for ip_addr in $(cat ipaddress.txt); do
ssh -t ${ip_addr} "bash -s" < /uploadscript.txt
done
#
#more /uploadscript.txt
sudo echo xy12ls1 | passwd --stdin martin

when I run this script I am getting this error message

$ ./remotescript
Pseudo-terminal will not be allocated because stdin is not a terminal.

Thanks,
# 7  
Old 04-10-2012
Try
Code:
-t -t

to force it to allocate a tty even though there's no local tty.
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