I was trying to setup an SSH connection with Github following this tutorial:
Testing your SSH connection
I came across the following command:
$ ssh -T git#github.com
# Attempts to ssh to github
Curious, I looked at the ssh manual. It said the following:
-T Disable pseudo-tty allocation.
What is tty allocation? What does tty stand for? Why are we disabling it?I earnestly tried to look it up but I was unable to find even a definition.
As explained in "gitolite: PTY allocation request failed on channel 0", it is important to do ssh test connection with -T, because some server could abort the transaction entirely if a text-terminal (tty) is requested.
-T avoids requesting said terminal, since GitHub has no intention of giving you an interactive secure shell, where you could type command.
GitHub only wants to reply to your ssh request, in order to ascertain that the ssh command does work (you have the right public/private keys, and the public one has been registered to your GitHub account)
PuTTy would be an example of a terminal emulator, serial console and network file transfer application. It supports several network protocols, including SCP, SSH, Telnet and rlogin.
The name "PuTTY" has no definitive meaning, though "tty" is the name for a terminal in the Unix tradition, usually held to be short for Teletype.
Other use-cases for -T (beside testing)
Transferring binary files
Execute commands on a remote server
SSH tunneling: ssh -fnT -L port:server:port user#server (-f for background: you don't want to execute command, don't need a TTY and just want to establish a tunnel)
Related
I want to run simulations in parallel in a remote Cluster calling them from matlab.
I manage to run them in my local Ubuntu machine using.
unix('parallel -j4 flow > /dev/null :::: Pool.txt');
But when I want it to run it in a remote cluster I really did not mange to make the parallel command to work.
The first problem was to avoid entering the password.
For that I used the sshpass as this
unix('sshpass -p password ssh user#cluster.example.com')
That get me in to the server but it does not continue to the next command line.
I try so many commands that I do not want to reference here.
But basically can some one that understands well the parallel GNU command usage tell me how can I connect to a cluster. and run the simulations there. is it better just to make a script at the server and run it from matlab?
Any expert advice is highly appreciated.
Your problem is not with GNU Parallel but with configuring ssh. First, you must get ssh set up, then the rest is easy.
So, on your local Ubuntu machine, you need to create your keys:
ssh-keygen -t rsa -b 2048
That will make some files in $HOME/.ssh. You now need to copy the public part of those keys to each and every node of the remote cluster where you want to run your parallel jobs:
ssh-copy-id -i $HOME/.ssh/id_rsa.pub CLUSTERUSERNAME#NODE-0
...
ssh-copy-id -i $HOME/.ssh/id_rsa.pub CLUSTERUSERNAME#NODE-15
e.g.
ssh-copy-id -i $HOME/.ssh/id_rsa.pub fred#192.168.0.100
Now, test you can ssh into each node:
ssh fred#node2
Then, on your local Ubuntu box, set up your config file for ssh, so it will be $HOME/.ssh/config
Host node0
Hostname 192.168.0.100
User fred
...
...
Host node15
Hostname 192.168.0.115
User fred
Now you can just use:
ssh node0
and it will know that means fred#192.168.0.100
Now GNU Parallel will work with:
parallel -S node0,node1,node2
We are trying to build CRAN reposiotry locally in windows using cwrsync. we are using rsync command to download all the packages etc. Since the machine where we are running is behind proxy we are also using RSYNC_PROXY variable. when we execute rsync command we are getting "rsync : did not see server greeting". Can you please help us.
rsync -av --chmod u+rwx -e "ssh -i d:\r-download" "/cygdrive/d/r-download"
rsync -rtlzv --delete cran.r-project.org::CRAN "/cygdrive/d/download"
Not sure whether its because of -e ssh.
Regards...Srini
Yes,
with daemon you cannot use '-e' ('--rsh') option.
From man page:
CONNECTING TO AN RSYNC DAEMON
It is also possible to use rsync without a remote shell as the
transport. In this case you will directly connect to a remote rsync
daemon, typically using TCP port 873. (This obviously requires the
daemon to be running on the remote system, so refer to the STARTING AN
RSYNC DAEMON TO ACCEPT CONNECTIONS section below for information on
that.)
Using rsync in this way is the same as using it with a remote shell
except that:
o you either use a double colon :: instead of a single colon to
separate the hostname from the path, or you use an rsync:// URL.
o the first word of the "path" is actually a module name.
o the remote daemon may print a message of the day when you
connect.
o if you specify no path name on the remote daemon then the list
of accessible paths on the daemon will be shown.
o if you specify no local destination then a listing of the
specified files on the remote daemon is provided.
o you must not specify the --rsh (-e) option.
Check last line.
Regards.
I have a Linux machine where I have created a cgi script (JarPatch.cgi), the code of which looks like this:
#!/usr/bin/perl
use warnings;
print "Content-type: text/html\n\n";
system ("sh JarPatch.sh");
The code of JarPatch.sh looks like this:
#!/bin/bash
echo "Inside jar patching tool";
PJS_DEV=app4915#slcai833.us.oracle.com;
ssh -f $PJS_DEV "cd /slot/ems4915/appmgr/tmp; echo stopping server ; ./find_stop_servers.sh;"
echo "Exit jar patching tool";
This script will basically shut down a server running on the remote machine
Problem statement is this:
When I execute this cgi script through Linux terminal. I can see that the ssh commands are getting executed. Server is shut down.
When I access the cgi script through a windows machine in a browser, the shell script is invoked but ssh seems not to be working.
Can any one give me a pointer to resolve this issue please?
I am new to perl/shell integration. So might be missing something small as well.
Thanks
When you ssh from windows machine all connections are made as webuser which is not authorized to ssh into remote machine. On other hand when you ssh from linux terminal you are able to ssh as user there is authorized to do so. This is because linux user has its ssh key on remote server.
You can also try to look into ProxyCommand which might come to rescue but i have no idea how it will work with windows.
Other approach is to create ssh keys for webuser and put them into remomte server which will be security risk.
When you run it as yourself ssh is offering your keys to authenticate you. When you run it through the webserver, the webserver user is trying to run the ssh command, and does not have your ssh keys to offer, so is probably being prompted for a password, and not successfully logging in.
You could fix this by generating ssh keys for the webserver user and sharing that key with the target system as well, which has some security implications to say the least.
I'm stuck in a bit of annoying situation.
There's a chain of machines between my desktop and the production servers. Something like this:
desktop -> firewall 1 -> firewall 2 -> prod_box 1
-> prod_box 2
-> ...
I'm looking for a way to automate deployment to the prod boxes via ssh.
I'm aware there are a number of solutions in general, but my restrictions are:
No changes permitted to firewall 2
No config changes permitted to prod boxes (only content)
firewall 1 has a local user account for me
firewall 2 and prod are accessed as root
port 22 is the only open port between each link
So, in general the command sequence I do to deploy is:
scp archive.tar user#firewall1:archive.tar
ssh user#firewall1
scp archive.tar root#firewall2:/tmp/archive.tar
ssh root#firewall2
scp /tmp/archive.tar root#prod1:/tmp/archive.tar
ssh root#prod1
cd /var/www/
tar xvf /tmp/archive.tar
Its a bit more complex than that in reality, but that's a basic summary of the tasks to do.
I've put my ssh key in firewall1:/home/user/.ssh/authorized_keys, so that's no problem.
However, I can't do this for firewall2 or prod boxes.
It'd be great if I could run this (commands above) from a shell script locally, type my password in 4 times and be done with it. Sadly I cannot figure out how to do that.
I need some way to chain ssh commands. I've spent all afternoon trying to use python to do this and eventually given up because the ssh libraries don't seem to support password-entry-style login.
What can I do here?
There must be some kind of library I can use to:
login via ssh using either a key file OR a dynamically entered password
remote remote shell commands through the chain of ssh tunnels
I'm not really sure what to tag this question, so I've just left it as ssh, deployment for now.
NB. It'd be great to use ssh tunnels and a deployment tool to push these changes out, but I'd still have to manually login to each box to setup the tunnel, and that wont work anyway, because of the port blocking.
I am working on Net::OpenSSH::Gateway, an extension for my other Perl module Net::OpenSSH that does just that.
For instance:
use Net::OpenSSH;
use Net::OpenSSH::Gateway;
my $gateway = Net::OpenSSH::Gateway->find_gateway(
proxies => ['ssh://user#firewall1',
'ssh://password:root#firewall2'],
backend => 'perl');
for my $host (#prod_hosts) {
my $ssh = Net::OpenSSH->new($host, gateway => $gateway);
if ($ssh->error) {
warn "unable to connect to $host\n";
next;
}
$ssh->scp_put($file_path, $destination)
or warn "scp for $host failed\n";
}
It requires Perl available in both firewalls, but no write permissions or installing any additional software there.
Unfortunately this isn't possible to do as one shell script. I did try, but ssh's password negotiation requires an interactive terminal, which you don't get with chained ssh commands. You could do it with passwordless keys, but since that's highly insecure and you can't do it anyway, nevermind.
The basic idea is that each server sends a bash script to the next one, which is then activated and sends the next one (and so on) until it reaches the last one, which does the distribution.
However, since this requires an interactive terminal at each stage, you're going to need to follow the payload down the chain manually executing each script as you go, somewhat as you do now but with less typing.
Obviously, you will need to customise them a bit, but try these scripts:
script1.sh
#!/bin/bash
user=doug
firewall1=firewall_1
#Minimise password entries across the board.
tar cf payload1.tar script3.sh archive.tar
tar cf payload2.tar script2.sh payload1.tar
scp payload2.tar ${user}#${firewall1}:payload2.tar
ssh ${user}#${firewall1} "tar xf payload2.tar;chmod +x script2.sh"
echo "Now connect to ${firewall1} and run ./script.sh"
script2.sh
#!/bin/bash
user=root
firewall2=firewall_2
# Minimise password entries
scp payload1.tar ${user}#${firewall2}:/tmp/payload1.tar
ssh ${user}#${firewall2} "cd /tmp;tar xf payload1.tar;chmod +x script3.sh"
echo "Now connect to ${firewall2} and run /tmp/script3.sh"
script3.sh
#!/bin/bash
user=root
hosts="prod1 prod2 prod3 prod4"
for host in $hosts
do
echo scp archive.tar ${user}#${host}:/tmp/archive.tar
echo ssh ${user}#${host} "cd /var/www; tar xvf /tmp/archive.tar"
done
It does require 3 password entries per firewall which is a bit annoying, but such is life.
This do you any good?
I was wondering if anyone has tried using teamcity's command line builder to perform ssh remote login.
Right now, I would like to automate some testing on a QNX neutrino OS which is currently unsupported by teamcity. As a work around, I setup a ssh server on the target qnx machine so i could ssh and sftp the executables in.
Firstly, the source are compiled on Windows XP using qnx's compiler (based on g++). Followed by sftp-ing the executables into qnx neutrino.
Next, using ssh, script the login to remotely start the test apps and send the results back to the remote agent for publishing.
The batch script I created works well standalone, however, after hooking it up on the remote agent, it fails to login ssh and hangs indefinitely at the following command:
ssh -l "./.sh"
Notes:
I have added the remote agent's RSA public key in the QNX .ssh/authorized keys file, automatic login is working.
Is there a need to add the teamcity server's RSA public key in too?
Anyone has any idea on this problem?
I had a few weird problems with key-based SSH logins on QNX related to file permissions for the keys in .ssh. and permissions of parent folders (/home/username and /root).
Add
LogLevel DEBUG3
to /etc/openssh/sshd_config, make sure syslog is configured and is logging sshd output, restart sshd and try again - it will most likely complain about something.
Also, ssh -l "./.sh" makes no sense - -l is used to specify the user name, something is off there.