My friend turned on remote login and I disabled it, but since he was already logged in, it didn't terminate the session(I knew he did it and we we're having a race).
He created a user account and I deleted the user account which terminated the session. In the future how can I terminate the ssh session?
I was trying to use these to no avail
w
~
ssh
ps -C ssh
ps. grep ssh
ps | grep ssh
pkill 1020
kill -9 1020
netstat -lnpt | awk '$4 ~ /:1234$/ {sub(/\/.*/, "", $7); print $7}'
sudo pkill loginwindow
Figured it out.
w //for established connections, get user name
ps -u <username> //for process id process name is sshd, get process id
sudo kill <process id>
enter password
Related
I am currently developing some work in clients and servers application and my college allows us to use their machines (linux) to host and test the apps.
My problem is that every single time I want to ssh into the machine the server prompts me to insert the password. I managed to use the information here to use a key in order to login but it still asks me for my password into the machine.
Using Putty I can save my password and login straight, is there anyway to do this using this command:
ssh -t (myUser#theSSHLink) -p 22
via Git Bash?
try:
USERHOST="myUser#theSSHLink"
cd ${HOME}
if [ ! -f ".ssh/id_rsa" ]; then
ssh-keygen -t rsa
fi
ssh $USERHOST mkdir -p .ssh
cat .ssh/id_rsa.pub | ssh $USERHOST 'cat >> .ssh/authorized_keys'
Running the above will ask for your password (from the user#host) twice. Afterwards, it shouldn't ask for a password when you try to ssh.
I have 1 server which is behind a NAT and a firewall and I have another in another location that is accessible via a domain. The server behind the NAT and firewall is running on a cloud environment and is designed to be disposable ie if it breaks we can simply redeploy it with a single script, in this case, it is OpenStack using a heat template. When that server fires up it runs the following command to create a reverse SSH tunnel to the server outside the NAT and Firewall to allow us to connect via port 8080 on that server. The issue I am having is it seems if that OpenSSH tunnel gets broken (server goes down maybe) the tunnel remains, meaning when we re-deploy the heat template to launch the server again it will no longer be able to connect to that port unless I kill the ssh process on the server outside the NAT beforehand.
here is the command I am using currently to start the reverse tunnel:
sudo ssh -f -N -T -R 9090:localhost:80 user#example.com
I had a similar issue, and fixed it this way:
First, at the server, I created in the home directory a script called .kill_tunel_ssh.sh with this contents:
#this finds the process that is opening the port 9090, finds its PID and kills it
sudo netstat -ltpun | grep 9090 | grep 127 | awk -F ' ' '{print $7}' | awk -F '/' '{print $1}' | xargs kill -9
Then, at the client, I created a script called connect_ssh.sh with this contents:
#this opens a ssh connection, runs the script .kill_tunnel_ssh.sh and exit
ssh user#remote.com "./.kill_tunel_ssh.sh"
#this opens a ssh connection opening the reverse tunnel
ssh user#remote.com -R 9090:localhost:80
Now, I always use connect_ssh.sh to open the SSH connection, instead of using the ssh command directly.
It requires the user at the remote host to have sudo configured without asking for password when executing the netstat command.
Maybe (probably) there is a better way to accomplish it, but that is working for me.
I'm currently running a bunch of:
sudo ssh -L PORT:IP:PORT root#IP
where IP is the target of a secured machine, and PORT represents the ports I'm forwarding.
This is because I use a lot of applications which I cannot access without this forwarding. After performing this, I can access through localhost:PORT.
The main problem occured now that I actually have 4 of these ports that I have to forward.
My solution is to open 4 shells and constantly search my history backwards to look for exactly which ports need to be forwarded etc, and then run this command - one in each shell (having to fill in passwords etc).
If only I could do something like:
sudo ssh -L PORT1+PORT2+PORT+3:IP:PORT+PORT2+PORT3 root#IP
then that would already really help.
Is there a way to make it easier to do this?
The -L option can be specified multiple times within the same command. Every time with different ports. I.e. ssh -L localPort0:ip:remotePort0 -L localPort1:ip:remotePort1 ...
Exactly what NaN answered, you specify multiple -L arguments. I do this all the time. Here is an example of multi port forwarding:
ssh remote-host -L 8822:REMOTE_IP_1:22 -L 9922:REMOTE_IP_2:22
Note: This is same as -L localhost:8822:REMOTE_IP_1:22 if you don't specify localhost.
Now with this, you can now (from another terminal) do:
ssh localhost -p 8822
to connect to REMOTE_IP_1 on port 22
and similarly
ssh localhost -p 9922
to connect to REMOTE_IP_2 on port 22
Of course, there is nothing stopping you from wrapping this into a script or automate it if you have many different host/ports to forward and to certain specific ones.
For people who are forwarding multiple port through the same host can setup something like this in their ~/.ssh/config
Host all-port-forwards
Hostname 10.122.0.3
User username
LocalForward PORT_1 IP:PORT_1
LocalForward PORT_2 IP:PORT_2
LocalForward PORT_3 IP:PORT_3
LocalForward PORT_4 IP:PORT_4
and it becomes a simple ssh all-port-forwards away.
You can use the following bash function (just add it to your ~/.bashrc):
function pfwd {
for i in ${#:2}
do
echo Forwarding port $i
ssh -N -L $i:localhost:$i $1 &
done
}
Usage example:
pfwd hostname {6000..6009}
jbchichoko and yuval have given viable solutions. But jbchichoko's answer isn't a flexible answer as a function, and the opened tunnels by yuval's answer cannot be shut down by ctrl+c because it runs in the background. I give my solution below solving both the two flaws:
Defing a function in ~/.bashrc or ~/.zshrc:
# fsshmap multiple ports
function fsshmap() {
echo -n "-L 1$1:127.0.0.1:$1 " > $HOME/sh/sshports.txt
for ((i=($1+1);i<$2;i++))
do
echo -n "-L 1$i:127.0.0.1:$i " >> $HOME/sh/sshports.txt
done
line=$(head -n 1 $HOME/sh/sshports.txt)
cline="ssh "$3" "$line
echo $cline
eval $cline
}
A example of running the function:
fsshmap 6000 6010 hostname
Result of this example:
You can access 127.0.0.1:16000~16009 the same as hostname:6000~6009
In my company both me and my team members need access to 3 ports of a non-reachable "target" server so I created a permanent tunnel (that is a tunnel that can run in background indefinitely, see params -f and -N) from a reachable server to the target one. On the command line of the reachable server I executed:
ssh root#reachableIP -f -N -L *:8822:targetIP:22 -L *:9006:targetIP:9006 -L *:9100:targetIP:9100
I used user root but your own user will work. You will have to enter the password of the chosen user (even if you are already connected to the reachable server with that user).
Now port 8822 of the reachable machine corresponds to port 22 of the target one (for ssh/PuTTY/WinSCP) and ports 9006 and 9100 on the reachable machine correspond to the same ports of the target one (they host two web services in my case).
Another one liner that I use and works on debian:
ssh user#192.168.1.10 $(for j in $(seq 20000 1 20100 ) ; do echo " -L$j:127.0.0.1:$j " ; done | tr -d "\n")
One of the benefits of logging into a server with port forwarding is facilitating the use of Jupyter Notebook. This link provides an excellent description of how to it. Here I would like to do some summary and expansion for all of you guys to refer.
Situation 1. Login from a local machine named Host-A (e.g. your own laptop) to a remote work machine named Host-B.
ssh user#Host-B -L port_A:localhost:port_B
jupyter notebook --NotebookApp.token='' --no-browser --port=port_B
Then you can open a browser and enter: http://localhost:port_A/ to do your work on Host-B but see it in Host-A.
Situation 2. Login from a local machine named Host-A (e.g. your own laptop) to a remote login machine named Host-B and from there login to the remote work machine named Host-C. This is usually the case for most analytical servers within universities and can be achieved by using two ssh -L connected with -t.
ssh -L port_A:localhost:port_B user#Host-B -t ssh -L port_B:localhost:port_C user#Host-C
jupyter notebook --NotebookApp.token='' --no-browser --port=port_C
Then you can open a browser and enter: http://localhost:port_A/ to do your work on Host-C but see it in Host-A.
Situation 3. Login from a local machine named Host-A (e.g. your own laptop) to a remote login machine named Host-B and from there login to the remote work machine named Host-C and finally login to the remote work machine Host-D. This is not usually the case but might happen sometime. It's an extension of Situation 2 and the same logic can be applied on more machines.
ssh -L port_A:localhost:port_B user#Host-B -t ssh -L port_B:localhost:port_C user#Host-C -t ssh -L port_C:localhost:port_D user#Host-D
jupyter notebook --NotebookApp.token='' --no-browser --port=port_D
Then you can open a browser and enter: http://localhost:port_A/ to do your work on Host-D but see it in Host-A.
Note that port_A, port_B, port_C, port_D can be random numbers except common port numbers listed here. In Situation 1, port_A and port_B can be the same to simplify the procedure.
Here is a solution inspired from the one from Yuval Atzmon.
It has a few benefits over the initial solution:
first it creates a single background process and not one per port
it generates the alias that allows you to kill your tunnels
it binds only to 127.0.0.1 which is a little more secure
You may use it as:
tnl your.remote.com 1234
tnl your.remote.com {1234,1235}
tnl your.remote.com {1234..1236}
And finally kill them all with tnlkill.
function tnl {
TUNNEL="ssh -N "
echo Port forwarding for ports:
for i in ${#:2}
do
echo " - $i"
TUNNEL="$TUNNEL -L 127.0.0.1:$i:localhost:$i"
done
TUNNEL="$TUNNEL $1"
$TUNNEL &
PID=$!
alias tnlkill="kill $PID && unalias tnlkill"
}
An alternative approach is to tell ssh to work as a SOCKS proxy using the -D flag.
That way you would be able to connect to any remote network address/port accesible through the ssh server as long as the client applications are able to go through a SOCKS proxy (or work with something like socksify).
If you want a simple solution that runs in the background and is easy to kill - use a control socket
# start
$ ssh -f -N -M -S $SOCKET -L localhost:9200:localhost:9200 $HOST
# stop
$ ssh -S $SOCKET -O exit $HOST
I've developed loco for help with ssh forwarding. It can be used to share ports 5000 and 7000 on remote locally at the same ports:
pip install loco
loco listen SSHINFO -r 5000 -r 7000
First It can be done using Parallel Execution by xargs -P 0.
Create a file for binding the ports e.g.
localhost:8080:localhost:8080
localhost:9090:localhost:8080
then run
xargs -P 0 -I xxx ssh -vNTCL xxx <REMOTE> < port-forward
or you can do a one-liner
echo localhost:{8080,9090} | tr ' ' '\n' | sed 's/.*/&:&/' | xargs -P 0 -I xxx ssh -vNTCL xxx <REMOTE>
pros independent ssh port-forwarding, they are independent == avoiding Single Point of Failure
cons each ssh port-forwarding is forked separately, somehow not efficient
second it can be done using curly brackets expansion feature in bash
echo "ssh -vNTC $(echo localhost:{10,20,30,40,50} | perl -lpe 's/[^ ]+/-L $&:$&/g') <REMOTE>"
# output
ssh -vNTC -L localhost:10:localhost:10 -L localhost:20:localhost:20 -L localhost:30:localhost:30 -L localhost:40:localhost:40 -L localhost:50:localhost:50 <REMOTE>
real example
echo "-vNTC $(echo localhost:{8080,9090} | perl -lpe 's/[^ ]+/-L $&:$&/g') gitlab" | xargs ssh
Forwarding 8080 and 9090 to gitlab server.
pros one single fork == efficient
cons by closing this process (ssh) all forwarding are closed == Single Point of Failure
You can use this zsh function (probably works with bash, too)(Put it in ~/.zshrc):
ashL () {
local a=() i
for i in "$#[2,-1]"
do
a+=(-L "${i}:localhost:${i}")
done
autossh -M 0 -o "ServerAliveInterval 30" -o "ServerAliveCountMax 3" -NT "$1" "$a[#]"
}
Examples:
ashL db#114.39.161.24 6480 7690 7477
ashL db#114.39.161.24 {6000..6050} # Forwards the whole range. This is simply shell syntax sugar.
Im trying to setup the passwordless SSh Login like the one stated here
I was able to generate the SSH Key Successfully
ssh-keygen
But when I'm doing this
cat ~/.ssh/id_dsa.pub | ssh user#xxx.xxx.xxx.xxx 'cat >>
~/.ssh/authorized_keys'
it gave me this error
Pseudo-terminal will not be allocated because stdin is not a terminal
ssh : xxx.xxx.xxx.xxxcat >> ~/.ssh/id_rsa.pub | ssh
user#xxx.xxx.xxx.xxx 'cat >>> ~/.ssh/authorized_keys'
I tried to setup passwordless SSH without getting this kind of error but its not working because it is still asking for password. And according to the author of this article, SSH-copy-id has 3 issues which most probably the reason why It still asking for password.
Any ideas?
Note: machines are running on CentOS
Try:
cat ~/.ssh/id_dsa.pub | ssh -t -t user#xxx.xxx.xxx.xxx 'cat >> ~/.ssh/authorized_keys'
-t -t option to force pseudo-tty allocation even if stdin isn't a terminal.
I have written a small bash script which needs an ssh tunnel to draw data from a remote server, so it prompts the user:
echo "Please open an ssh tunnel using 'ssh -L 6000:localhost:5432 example.com'"
I would like to check whether the user had opened this tunnel, and exit with an error message if no tunnel exist. Is there any way to query the ssh tunnel, i.e. check if the local port 6000 is really tunneled to that server?
Netcat is your friend:
nc -z localhost 6000 || echo "no tunnel open"
This is my test. Hope it is useful.
# $COMMAND is the command used to create the reverse ssh tunnel
COMMAND="ssh -p $SSH_PORT -q -N -R $REMOTE_HOST:$REMOTE_HTTP_PORT:localhost:80 $USER_NAME#$REMOTE_HOST"
# Is the tunnel up? Perform two tests:
# 1. Check for relevant process ($COMMAND)
pgrep -f -x "$COMMAND" > /dev/null 2>&1 || $COMMAND
# 2. Test tunnel by looking at "netstat" output on $REMOTE_HOST
ssh -p $SSH_PORT $USER_NAME#$REMOTE_HOST netstat -an | egrep "tcp.*:$REMOTE_HTTP_PORT.*LISTEN" \
> /dev/null 2>&1
if [ $? -ne 0 ] ; then
pkill -f -x "$COMMAND"
$COMMAND
fi
Autossh is best option - checking process is not working in all cases (e.g. zombie process, network related problems)
example:
autossh -M 2323 -c arcfour -f -N -L 8088:localhost:80 host2
This is really more of a serverfault-type question, but you can use netstat.
something like:
# netstat -lpnt | grep 6000 | grep ssh
This will tell you if there's an ssh process listening on the specified port. it will also tell you the PID of the process.
If you really want to double-check that the ssh process was started with the right options, you can then look up the process by PID in something like
# ps aux | grep PID
Use autossh. It's the tool that's meant for monitoring the ssh connection.
We can check using ps command
# ps -aux | grep ssh
Will show all shh service running and we can find the tunnel service listed
These are more detailed steps to test or troubleshoot an SSH tunnel. You can use some of them in a script. I'm adding this answer because I had to troubleshoot the link between two applications after they stopped working. Just grepping for the ssh process wasn't enough, as it was still there. And I couldn't use nc -z because that option wasn't available on my incantation of netcat.
Let's start from the beginning. Assume there is a machine, which will be called local with IP address 10.0.0.1 and another, called remote, at 10.0.3.12. I will prepend these hostnames, to the commands below, so it's obvious where they're being executed.
The goal is to create a tunnel that will forward TCP traffic from the loopback address on the remote machine on port 123 to the local machine on port 456. This can be done with the following command, on the local machine:
local:~# ssh -N -R 123:127.0.0.1:456 10.0.3.12
To check that the process is running, we can do:
local:~# ps aux | grep ssh
If you see the command in the output, we can proceed. Otherwise, check that the SSH key is installed in the remote. Note that excluding the username before the remote IP, makes ssh use the current username.
Next, we want to check that the tunnel is open on the remote:
remote:~# netstat | grep 10.0.0.1
We should get an output similar to this:
tcp 0 0 10.0.3.12:ssh 10.0.0.1:45988 ESTABLISHED
Would be nice to actually see some data going through from the remote to the host. This is where netcat comes in. On CentOS it can be installed with yum install nc.
First, open a listening port on the local machine:
local:~# nc -l 127.0.0.1:456
Then make a connection on the remote:
remote:~# nc 127.0.0.1 123
If you open a second terminal to the local machine, you can see the connection. Something like this:
local:~# netstat | grep 456
tcp 0 0 localhost.localdom:456 localhost.localdo:33826 ESTABLISHED
tcp 0 0 localhost.localdo:33826 localhost.localdom:456 ESTABLISHED
Better still, go ahead and type something on the remote:
remote:~# nc 127.0.0.1 8888
Hallo?
anyone there?
You should see this being mirrored on the local terminal:
local:~# nc -l 127.0.0.1:456
Hallo?
anyone there?
The tunnel is working! But what if you have an application, called appname, which is supposed to be listening on port 456 on the local machine? Terminate nc on both sides then run your application. You can check that it's listening on the correct port with this:
local:~# netstat -tulpn | grep LISTEN | grep appname
tcp 0 0 127.0.0.1:456 0.0.0.0:* LISTEN 2964/appname
By the way, running the same command on the remote should show sshd listening on port 127.0.0.1:123.
#!/bin/bash
# Check do we have tunnel to example.com server
lsof -i tcp#localhost:6000 > /dev/null
# If exit code wasn't 0 then tunnel doesn't exist.
if [ $? -eq 1 ]
then
echo ' > You missing ssh tunnel. Creating one..'
ssh -L 6000:localhost:5432 example.com
fi
echo ' > DO YOUR STUFF < '
stunnel is a good tool to make semi-permanent connections between hosts.
http://www.stunnel.org/
If you are using ssh in background, use this:
sudo lsof -i -n | egrep '\<ssh\>'