Ssh to an array of servers in a for loop

Shell Programming and Scripting
1

There are 4 remote hosts that I have stored in an array. A ssh trust has been created from the local host to each of the remote hosts.
I am trying to ssh to each of the servers in a for loop as shown below.

declare -a host
 host[${#host[@]}]="server1"
 host[${#host[@]}]="server2"
 host[${#host[@]}]="server3"
 host[${#host[@]}]="server4"

for host in "${host[@]}"
do
  ssh -qtt user@${host} "sh -s "${version}""  <  test.sh
done

test.sh is a file on the local server that I am running on the remote host after I ssh to the remote host. But it is terminating after the first iteration. If I use -n switch it prompts me for password in the second iteration.

Please can you guide me on this issue.

Thanks!

2

You cannot double quote double quotes. You could escape them with \, or just use a single quote.

ssh -qtt user@${host} "sh -s '${version}'"  <  test.sh
3 
for host in "${host[@]}"
do
ssh -qtt ohsadm@${host} "sh -s '${version}'"  <  test_steps.sh
done

exits after the first iteration. host array has 4 servers. I want the ssh in the for loop to run through all the 4 servers.

4

Hi,
Try with -n -o BatchMode=yes options:
-n for manage stdin
-o BatchMode=yes for no ask password

Regards.

5

You do not want -n when running a script read from stdin! This is not the usual stdin problem.

Can you show your complete, unmodified script? I think something funny is going on here.

6

I am able to iterate successfully through the array if I specify the commands as mentioned below.

for host in "${host[@]}"
do
  echo $host
  ssh -qtt user@${host} "cd /build && cp -p web.zip web.zip_${version} && rm -rf test && unzip /build/web.zip && cd /bin ";  done;

However, if I try to add the commands in a separate file called test.sh and stream it to ssh as shown below, it exits after the first iteration. Pressing Ctrl-C manually triggers the next iteration.

for host in "${host[@]}"
do
  ssh -qtt user@${host} "sh -s "${version}""  <  test.sh
done
7

I repeat: You cannot put double quotes inside double quotes that way.

This is wrong:

"sh -s "${version}""

This would be more correct:

"sh -s '${version}'"

I just realized, however -- your test.sh probably uses the ${version} variable, which is why you are feeding it into sh, yes? You want it to carry over. But arguments to sh -s don't work that way, you don't get the names, just $1 $2 $3. Not to mention, you need -- if you want it to assume the following are arguments. Try this:

$ sh -s -- a b c
$ echo $1

a

$ echo $2

b

$ echo $3

c

$ exit
$

So I think you actually want:

ssh -qtt user@${host} "sh -s -- '${version}'"  <  test.sh

...and your script should be using $1 and not ${version} .

I suspect you can omit the -tt completely, too. I see no commands in there that actually need a terminal, and throwing one into the mix when not needed seldom helps.

8

A construct I often use:

ssh username@host exec sh -s -- "arg1" "arg2" "arg3" <<"EOF"

# Literal, unescaped script contents to be executed on the remote side.

echo "arg1 is $1"
echo "arg2 is $2"
echo "arg3 is $3"

# The EOF must be at the beginning of the line and not indented.
EOF
9

test.sh contains the commands.

ssh -qtt user@$host "sh -s '${version}'" < test.sh

works absolutely fine. I run into issues only while looping.

10

??? That makes no sense. Why would you feed ssh username@host into ssh username@host ? That instructs the remote host to try and ssh into itself, but will fail because $host and $version are unset and test.sh does not exist. I am extremely suspicious of this ever working, especially since only now have you fixed the syntax errors that I noticed...

This test.sh needs to be a separate file, not the same one, so it can contain this:

cd /build && cp -p web.zip web.zip_${1} && rm -rf test && unzip /build/web.zip && cd /bin

Note the $1 instead of $version, for reasons I gave earlier.

Then you should do

ssh username@host exec /bin/sh -s -- ${version} < test.sh

and have the remote host run the sequence of commands stored in test.sh.

Try it without the -qtt. That may misbehave when you don't have a terminal or want it to be interactive.