Create SSH Connection Independent Of Calling Bash Script - linux

I am trying to create a bash script that serves as a wrapper for numerous ssh connection options. Basically the user will run the script and the appropriate ssh command will then be created and executed based on their selections. I am trying to find a way to have the script exit and the ssh connection created, rather than having the script continue to run while the user is working on the remote server. Does anyone know if this is possible or how I could achieve this? Thanks!
Edit
Sorry, I should have posted my code:
display_main_menu(){
while true
do
clear
echo ""
echo " Select A Server:"
echo " -------------------------------"
echo " 1) Server 1"
echo " 2) Server 2"
echo " 3) Server 3"
echo " 4) Quit"
local selection
read -p " Enter choice [1 - 4] " selection
case $selection in
1)
# Open SSH Connection to Server 1
break
;;
2)
# Open SSH Connection to Server 2
break
;;
3)
# Open SSH Connection to Server 3
break
;;
4)
exit 0
break
;;
;;
*)
echo -e "Invalid Selection..." && sleep 2
;;
esac
done
}

Use:
exec ssh <pararameters>
The exec builtin command:
Synopsis
exec [-a NAME] [-cl] [COMMAND] [ARG...] [REDIRECTION...]
Description
The exec builtin command is used to
replace the shell with a given program (executing it, not as new
process)
set redirections for the program to execute or for the
current shell
If only redirections are given, the redirections affect the current shell without executing any program.

Related

`qdbus` command does not apply until scripts exits

I have a script which I use to make it easier for me to connect to the many servers I need to SSH into. It's working well except that the terminal's title (Konsole tab title in my case) is being set to the name of my script, "() ./scripts/ssh". I updated the script and added a call to qdbus to set the Konsole tab title. It works, but only after the SSH session is closed / the script completes.
How do I make the qdbus command take affect immediately?
the script
#!/bin/bash
ENV=$1
HOST=$2
USER=${3:-my_username}
if [ -z ${ENV} ]; then
echo "First parameter must be the environment."
exit -1
fi
if [ -z ${HOST} ]; then
echo "Second parameter must be the host."
exit -1
fi
case "$ENV" in
# cases to determine proper hostname from abbreviated input
*)
echo "Unsupported environment: ${ENV}"
exit -1
esac
HOST="${HOST}.${ENV}.net"
# set tab title
qdbus >/dev/null "${KONSOLE_DBUS_SERVICE}" ${KONSOLE_DBUS_SESSION} setTabTitleFormat 0 "${USER}#${HOST}"
echo "Connecting to ${HOST} as ${USER} ..."
ssh ${USER}#${HOST}
# revert tab title -- COMMENTED OUT FOR TESTING
# qdbus >/dev/null "${KONSOLE_DBUS_SERVICE}" ${KONSOLE_DBUS_SESSION} setTabTitleFormat 0 "%w"
When I run my script ...
tab text is updated to () ./scripts/ssh
"Connecting" echo is displayed
I'm SSH'd in per usual
tab text is not updated
When I exit the SSH session, the tab text is set to "${USER}#${HOST}" as in the command above (before ssh).
I have added / comment out a line which reverts the tab text back to what it was before I ran the script (I think).

Execute Bash script remotely via cURL

I have a simple Bash script that takes in inputs and prints a few lines out with that inputs
fortinetTest.sh
read -p "Enter SSC IP: $ip " ip && ip=${ip:-1.1.1.1}
printf "\n"
#check IP validation
if [[ $ip =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
echo "SSC IP: $ip"
printf "\n"
else
echo "Enter a valid SSC IP address. Ex. 1.1.1.1"
exit
fi
I tried to upload them into my server, then try to run it via curl
I am not sure why the input prompt never kick in when I use cURL/wget.
Am I missing anything?
With the curl ... | bash form, bash's stdin is reading the script, so stdin is not available for the read command.
Try using a Process Substitution to invoke the remote script like a local file:
bash <( curl -s ... )
Your issue can be simply be reproduced by run the script like below
$ cat test.sh | bash
Enter a valid SSC IP address. Ex. 1.1.1.1
This is because the bash you launch with a pipe is not getting a TTY, when you do a read -p it is read from stdin which is content of the test.sh in this case. So the issue is not with curl. The issue is not reading from the tty
So the fix is to make sure you ready it from tty
read < /dev/tty -p "Enter SSC IP: $ip " ip && ip=${ip:-1.1.1.1}
printf "\n"
#check IP validation
if [[ $ip =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
echo "SSC IP: $ip"
printf "\n"
else
echo "Enter a valid SSC IP address. Ex. 1.1.1.1"
exit
fi
Once you do that even curl will start working
vagrant#vagrant:/var/www/html$ curl -s localhost/test.sh | bash
Enter SSC IP: 2.2.2.2
SSC IP: 2.2.2.2
I personally prefer source <(curl -s localhost/test.sh) option. While it is similar to bash ..., the one significant difference is how processes handled.
bash will result in a new process being spun up, and that process will evoke commands from the script.
source on the other hand will use current process to evoke commands from the script.
In some cases that can play a key role. I admit that is not very often though.
To demonstrate do the following:
### Open Two Terminals
# In the first terminal run:
echo "sleep 5" > ./myTest.sh
bash ./myTest.sh
# Switch to the second terminal and run:
ps -efjh
## Repeat the same with _source_ command
# In the first terminal run:
source ./myTest.sh
# Switch to the second terminal and run:
ps -efjh
Results should look similar to this:
Before execution:
Running bash (main + two subprocesses):
Running source (main + one subprocess):
UPDATE:
Difference in use variable usage by bash and source:
source command will use your current environment. Meaning that upon execution all changes and variable declarations, made by the script, will be available in your prompt.
bash on the other hand will be running in as a different process; therefore, all variables will be discarded when process exits.
I think everyone will agree that there are benefits and drawbacks to each method. You just have to decide which one is better for your use case.
## Test for variables declared by the script:
echo "test_var3='Some Other Value'" > ./myTest3.sh
bash ./myTest3.sh
echo $test_var3
source ./myTest3.sh
echo $test_var3
## Test for usability of current environment variables:
test_var="Some Value" # Setting a variable
echo "echo $test_var" > myTest2.sh # Creating a test script
chmod +x ./myTest2.sh # Adding execute permission
## Executing:
. myTest2.sh
bash ./myTest2.sh
source ./myTest2.sh
./myTest2.sh
## All of the above results should print the variable.
I hope this helps.

How to get exit code of remote command through ssh

I am running a script from remote machine via ssh:
ssh 'some_cmd;my_script'
Now, I want to store exit status of shell script on my local machine.
How can I do it?
Assuming nothing goes wrong with ssh itself, its exit status is the exit status of the last command executed on the remote host. (If something does go wrong, its exit status is 255.)
$ ssh remotehost exit 13
$ echo $?
13
I had same problem. I don't think the previous answers will work (at least, they did not work for me).
This is what worked for me: I ran my command and displayed the exit code and captured it in a variable.
Ensure you protect the $? sign with the escape sequence, \:
# retcode=$(ssh test#1.2.3.4 "grep -q test /etc/passwd ; echo \$? " 2>/dev/null)
# echo $retcode
# 1

Why this Debian-Linux autostart netcat script won't autostart?

I placed a link to my scripts in the rc.local to autostart it on linux debian boot. It starts and then stops at the while loop. It's a netcat script that listens permantently on port 4001.
echo "Start"
while read -r line
do
#some stuff to do
done < <(nc -l -p 4001)
When I start this script as root with command ./myscript it works 100% correctly. Need nc (netcat) root level access or something else?
EDIT:
rc.local
#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
/etc/samba/SQLScripts
exit 0
rc.local starts my script "SQLScripts"
SQLScripts
#! /bin/sh
# The following part always gets executed.
echo "Starting SQL Scripts" >> /var/log/SQLScriptsStart
/etc/samba/PLCCheck >> /var/log/PLCCheck &
"SQLScripts" starts "PLCCheck" (for example only one)
PLCCheck
#!/bin/bash
echo "before SLEEP" >> /var/log/PLCCheck
sleep 5
echo "after SLEEP" >> /var/log/PLCCheck
echo "vor While" >> /var/log/PLCCheck
while read -r line
do
echo "in While" >> /var/log/PLCCheck
done < <(netcat -u -l -p 6001)
In an rc script you have root level access by default. What does "it stops at the while loop" mean? It quits after a while, or so? I guess you need to run your loop in the background in order to achieve functionality usual in autostart scripts:
echo "Starting"
( while read -r line
do
#some stuff to do
done << (nc -l -p 4001) ) &
echo "Started with pid $( jobs -p )"
I have tested yersterday approximatly the same things, and I have discover that you can bypass the system and execute your netcat script with the following crontask. :
(every minute, but you can ajust that as you want.)
* * * * * /home/kali/script-netcat.sh // working for me
#reboot /home/kali/script-netcat.sh // this is blocked by the system.
According to me, I think that by default debian (and maybe others linux distrib) block every script that try to execute a netcat command.

Adding a service startup script for Amazon linux AMI

I am using an Amazon Linux AMI and doing some custom modifications(added an axis2server, etc) on it and saving it as a new AMI. Now what I want to do is when the AMI boots up, start up axis2server(ie.axis2server should automatically start when the instance boots up). For that I used a init script like below and ran the following command:
chkconfig --add axisservice
But when I launch a new instance from my image, the axis2server is not getting started.
I just only need to execute the script /home/ec2-user/axis2-1.6.1/bin/axis2server.sh at startup. Am I missing anything here?
#! /bin/sh
# Basic support for IRIX style chkconfig
###
# chkconfig: 235 98 55
# description: Manages the services you are controlling with the chkconfig command
###
case "$1" in
start)
echo -n "Starting axisservice"
touch ~/temp.txt
cd /home/ec2-user/axis2-1.6.1/bin
./axis2server.sh &
echo "."
;;
stop)
echo -n "Stopping axisservice"
echo "."
;;
*)
echo "Usage: /sbin/service axisservice {start|stop}"
exit 1
esac
exit 0
I went through https://help.ubuntu.com/community/CloudInit as well and it provides a mechanism called User-Data Scripts, where a user can execute a script when launching the script.
$ euca-run-instances --key mykey --user-data-file myscript.sh ami-axxxx
This is a command line option and what I want is something like when I launch the instance through the UI, the script should be started.Therefore, I think the above option can not be used in my case. Please correct me if I am wrong.
Thanks,
H.
I bet the environment is not set(up correctly). This means that I am guessing that your shell script tries to start another program and it's not to be found.
So at first, I'd adjust the start part of your script (current):
echo -n "Starting axisservice"
touch ~/temp.txt
cd /home/ec2-user/axis2-1.6.1/bin
./axis2server.sh &
echo "."
Edited:
echo -n "Starting axisservice"
touch ~/temp.txt
cd /home/ec2-user/axis2-1.6.1/bin
./axis2server.sh
RETVAL=$?
[ $RETVAL -eq 0 ] && echo Success
[ $RETVAL -ne 0 ] && echo Failure
echo "."
So what did I do?
removed & so script waits for your shell script (axis2server.sh) to complete
checked the return status ($?) of your shell script
Further debugging:
Add set -x to your scripts to enable tracing and log both stderr and stdout.
Questions:
Are you are aware that stop (in your service script) doesn't do anything?
touch ~/temp.txt is that supposed to create /root/temp.txt? (I'm guessing root runs this script.)
If none of my suggestions work, can you share axis2server.sh and paste stderr and stdout?

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