On Linux. I need to write a file containing a script.
My script should connect to a server, create a screen and execute a command. Several times automatically.
Pseudocode of the script:
ssh machine1
cd project_folder
screen -S screenA
python run.py -x
exit
screen -S screenB
python run.py -y
exit
exit
ssh machine2
cd project_folder
screen -S screenA
python run.py -z
exit
screen -S screenB
python run.py -t
exit
exit
ATM I can just connect and run each command manually.
Yes, thanks https://stackoverflow.com/users/9215267/siddharth-dushantha
And for the part of screen the code is
screen -dmS screen0
screen -ls
screen -r screen0 -p 0 -X stuff "the_command1^M"
screen -r screen0 -p 0 -X stuff "the_command2^M"
where ^M types enter at the end of the line.
Using osascript, I'm able to tell the Terminal application to open an ssh connection in a separate terminal window, however, I run into errors when trying to pass bash variables in the script.
This script works just fine:
osascript -e 'tell app "Terminal"
do script "ssh user#hostname -p port -L 9999:localhost:80 -i keyfile"
end tell'
...more commands...
But running a script like this one...
read -p "Port: " prt
read -p "Localhost port: " lhprt
osascript -e 'tell app "Terminal"
do script "ssh user#hostname -p \"$prt\" -L \"$lhprt\":localhost:80 -i keyfile"
end tell'
...more commands...
It doesn't pass the variables, i.e. the command passed in the new terminal window is
ssh user#hostname -p "$prt"
How might I format this to make it so my bash variables get fed through?
Just invert the quote type
Using single quote is preventing the shell to expand your parameters
Edit:
You can close the string just around your variables too.
I.e.
'this is a '$variable' in a "string".'
I'm trying to run a script in a tmux environment on another computer using ssh, but the ssh connection won't terminate until the script has finished. Let me explain this in detail:
This is test_ssh.sh:
#!/bin/bash
name="computername"
ssh $name /bin/bash <<\EOF
cd /scratch
mkdir test
cd test
cp /home/user/test_tmux3.sh .
tmux -c ./test_tmux3.sh &
echo 1 # at this point it waits until test_tmux3.sh is finished, instead of exiting :(
EOF
This is test_tmux3.sh (as a test to see if anything happens):
#!/bin/bash
mkdir 0min
sleep 60
mkdir 1min
sleep 60
mkdir 2min
At the end I would like to loop over multiple computers ($name) to start a script on each of them. The problem I am having right now is that test_ssh.sh waits after the echo 1 and only exits after tmux -c test_tmux3.sh & is finished (after 2 minutes). If I manually enter control-C test_ssh.sh stops and tmux -c test_tmux3.sh & continues running on the computer $name (which is what I want). How can automate that last step and get ssh to exit on its own?
Start the command in a detached tmux session.
#!/bin/bash
name="computername"
ssh $name /bin/bash <<\EOF
mkdir /scratch/test
cd /scratch/test
cp /home/user/test_tmux3.sh .
tmux new-session -d ./test_tmux3.sh
echo 1
EOF
Now, the tmux command will exit as soon as the new session is created and the script is started in that session.
Have you tried to use nohup command to tell to the process keep running after exit?:
#!/bin/bash
name="computername"
ssh $name /bin/bash <<\EOF
cd /scratch
mkdir test
cd test
cp /home/user/test_tmux3.sh .
nohup tmux -c ./test_tmux3.sh &
echo 1 # at this point it waits until test_tmux3.sh is finished, instead of exiting :(
EOF
I try ps aux and ps and pgrep myprocess and pidof myprocess but all say my script is not running (while my script is actually running). I check these command with ssh.
Do you have any idea?
If you use ssh to have to watch the pid you are actually sending
So run pgrep like this, ssh returns the exit status from the command you run:
ssh myserver 'pgrep -u username scriptname'
[ $? -eq 0 ] && echo 'Running' || echo "Not running"
username is the name of the user that started the process ex: root, daniyal, santa, or maybe jim
scriptname the actual name of the script file ex: myscript.sh, fixit.sh, or maybe foo.sh
This is a follow-on question to the How do you use ssh in a shell script? question. If I want to execute a command on the remote machine that runs in the background on that machine, how do I get the ssh command to return? When I try to just include the ampersand (&) at the end of the command it just hangs. The exact form of the command looks like this:
ssh user#target "cd /some/directory; program-to-execute &"
Any ideas? One thing to note is that logins to the target machine always produce a text banner and I have SSH keys set up so no password is required.
I had this problem in a program I wrote a year ago -- turns out the answer is rather complicated. You'll need to use nohup as well as output redirection, as explained in the wikipedia artcle on nohup, copied here for your convenience.
Nohuping backgrounded jobs is for
example useful when logged in via SSH,
since backgrounded jobs can cause the
shell to hang on logout due to a race
condition [2]. This problem can also
be overcome by redirecting all three
I/O streams:
nohup myprogram > foo.out 2> foo.err < /dev/null &
This has been the cleanest way to do it for me:-
ssh -n -f user#host "sh -c 'cd /whereever; nohup ./whatever > /dev/null 2>&1 &'"
The only thing running after this is the actual command on the remote machine
Redirect fd's
Output needs to be redirected with &>/dev/null which redirects both stderr and stdout to /dev/null and is a synonym of >/dev/null 2>/dev/null or >/dev/null 2>&1.
Parantheses
The best way is to use sh -c '( ( command ) & )' where command is anything.
ssh askapache 'sh -c "( ( nohup chown -R ask:ask /www/askapache.com &>/dev/null ) & )"'
Nohup Shell
You can also use nohup directly to launch the shell:
ssh askapache 'nohup sh -c "( ( chown -R ask:ask /www/askapache.com &>/dev/null ) & )"'
Nice Launch
Another trick is to use nice to launch the command/shell:
ssh askapache 'nice -n 19 sh -c "( ( nohup chown -R ask:ask /www/askapache.com &>/dev/null ) & )"'
If you don't/can't keep the connection open you could use screen, if you have the rights to install it.
user#localhost $ screen -t remote-command
user#localhost $ ssh user#target # now inside of a screen session
user#remotehost $ cd /some/directory; program-to-execute &
To detach the screen session: ctrl-a d
To list screen sessions:
screen -ls
To reattach a session:
screen -d -r remote-command
Note that screen can also create multiple shells within each session. A similar effect can be achieved with tmux.
user#localhost $ tmux
user#localhost $ ssh user#target # now inside of a tmux session
user#remotehost $ cd /some/directory; program-to-execute &
To detach the tmux session: ctrl-b d
To list screen sessions:
tmux list-sessions
To reattach a session:
tmux attach <session number>
The default tmux control key, 'ctrl-b', is somewhat difficult to use but there are several example tmux configs that ship with tmux that you can try.
I just wanted to show a working example that you can cut and paste:
ssh REMOTE "sh -c \"(nohup sleep 30; touch nohup-exit) > /dev/null &\""
You can do this without nohup:
ssh user#host 'myprogram >out.log 2>err.log &'
Quickest and easiest way is to use the 'at' command:
ssh user#target "at now -f /home/foo.sh"
I think you'll have to combine a couple of these answers to get what you want. If you use nohup in conjunction with the semicolon, and wrap the whole thing in quotes, then you get:
ssh user#target "cd /some/directory; nohup myprogram > foo.out 2> foo.err < /dev/null"
which seems to work for me. With nohup, you don't need to append the & to the command to be run. Also, if you don't need to read any of the output of the command, you can use
ssh user#target "cd /some/directory; nohup myprogram > /dev/null 2>&1"
to redirect all output to /dev/null.
This worked for me may times:
ssh -x remoteServer "cd yourRemoteDir; ./yourRemoteScript.sh </dev/null >/dev/null 2>&1 & "
You can do it like this...
sudo /home/script.sh -opt1 > /tmp/script.out &
It appeared quite convenient for me to have a remote tmux session using the tmux new -d <shell cmd> syntax like this:
ssh someone#elsewhere 'tmux new -d sleep 600'
This will launch new session on elsewhere host and ssh command on local machine will return to shell almost instantly. You can then ssh to the remote host and tmux attach to that session. Note that there's nothing about local tmux running, only remote!
Also, if you want your session to persist after the job is done, simply add a shell launcher after your command, but don't forget to enclose in quotes:
ssh someone#elsewhere 'tmux new -d "~/myscript.sh; bash"'
Actually, whenever I need to run a command on a remote machine that's complicated, I like to put the command in a script on the destination machine, and just run that script using ssh.
For example:
# simple_script.sh (located on remote server)
#!/bin/bash
cat /var/log/messages | grep <some value> | awk -F " " '{print $8}'
And then I just run this command on the source machine:
ssh user#ip "/path/to/simple_script.sh"
If you run remote command without allocating tty, redirect stdout/stderr works, nohup is not necessary.
ssh user#host 'background command &>/dev/null &'
If you use -t to allocate tty to run interactive command along with background command, and background command is the last command, like this:
ssh -t user#host 'bash -c "interactive command; nohup backgroud command &>/dev/null &"'
It's possible that background command doesn't actually start. There's race here:
bash exits after nohup starts. As a session leader, bash exit results in HUP signal sent to nohup process.
nohup ignores HUP signal.
If 1 completes before 2, the nohup process will exit and won't start the background command at all. We need to wait nohup start the background command. A simple workaroung is to just add a sleep:
ssh -t user#host 'bash -c "interactive command; nohup backgroud command &>/dev/null & sleep 1"'
The question was asked and answered years ago, I don't know if openssh behavior changed since then. I was testing on:
OpenSSH_8.6p1, OpenSSL 1.1.1g FIPS 21 Apr 2020
I was trying to do the same thing, but with the added complexity that I was trying to do it from Java. So on one machine running java, I was trying to run a script on another machine, in the background (with nohup).
From the command line, here is what worked: (you may not need the "-i keyFile" if you don't need it to ssh to the host)
ssh -i keyFile user#host bash -c "\"nohup ./script arg1 arg2 > output.txt 2>&1 &\""
Note that to my command line, there is one argument after the "-c", which is all in quotes. But for it to work on the other end, it still needs the quotes, so I had to put escaped quotes within it.
From java, here is what worked:
ProcessBuilder b = new ProcessBuilder("ssh", "-i", "keyFile", "bash", "-c",
"\"nohup ./script arg1 arg2 > output.txt 2>&1 &\"");
Process process = b.start();
// then read from process.getInputStream() and close it.
It took a bit of trial & error to get this working, but it seems to work well now.
YOUR-COMMAND &> YOUR-LOG.log &
This should run the command and assign a process id you can simply tail -f YOUR-LOG.log to see results written to it as they happen. you can log out anytime and the process will carry on
If you are using zsh then use program-to-execute &! is a zsh-specific shortcut to both background and disown the process, such that exiting the shell will leave it running.
A follow-on to #cmcginty's concise working example which also shows how to alternatively wrap the outer command in double quotes. This is how the template would look if invoked from within a PowerShell script (which can only interpolate variables from within double-quotes and ignores any variable expansion when wrapped in single quotes):
ssh user#server "sh -c `"($cmd) &>/dev/null </dev/null &`""
Inner double-quotes are escaped with back-tick instead of backslash. This allows $cmd to be composed by the PowerShell script, e.g. for deployment scripts and automation and the like. $cmd can even contain a multi-line heredoc if composed with unix LF.
First follow this procedure:
Log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:
a#A:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa):
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a#A
Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):
a#A:~> ssh b#B mkdir -p .ssh
b#B's password:
Finally append a's new public key to b#B:.ssh/authorized_keys and enter b's password one last time:
a#A:~> cat .ssh/id_rsa.pub | ssh b#B 'cat >> .ssh/authorized_keys'
b#B's password:
From now on you can log into B as b from A as a without password:
a#A:~> ssh b#B
then this will work without entering a password
ssh b#B "cd /some/directory; program-to-execute &"
I think this is what you need:
At first you need to install sshpass on your machine.
then you can write your own script:
while read pass port user ip; do
sshpass -p$pass ssh -p $port $user#$ip <<ENDSSH1
COMMAND 1
.
.
.
COMMAND n
ENDSSH1
done <<____HERE
PASS PORT USER IP
. . . .
. . . .
. . . .
PASS PORT USER IP
____HERE