Hi I have a list of few hundred hosts. I want to run a command using ssh in a loop, if my ssh keys are set properly, then I execute a command if I get challenge for password I want to skip to the next host
So lets say I have hosta and hostb and hostc. I can do a ssh to hosta & hostc , but hostb is challenging me for password. Is there a way to check if a hosts will challenge me for password or not? So my logic would be
if I get challenge from $host; then
skip host
else
ssh $host 'command'
fi
I hope this makes sense. Thanking you in advance
for host in host1 host2 host3; do
ssh -o PasswordAuthentication=no $host command
done
To make it parallel add &:
for host in host1 host2 host3; do
ssh -o PasswordAuthentication=no $host command &
done
If this is a thing you do regularly, I would suggest looking at dsh.
http://www.tecmint.com/using-dsh-distributed-shell-to-run-linux-commands-across-multiple-machines/
it allows you to make a list of your servers, and run commands against ALL of them, or just subsets(web, db, app, etc)
you can create global files, or create your own personal files.
ssh has an option, called BatchMode.
You can use it like
ssh -o BatchMode ...
and it won't ask you anything, but skip the connection attempt.
Or use rundeck - this can be found at http://rundeck.org
Related
I have a bash script running on a host with IP1. The script does a ssh to a remote host with IP2
ssh ubuntu#IP2 "ls -l ~"
The ssh replies with a
The authenticity of host 'IP2 (IP2)' can't be established.
ECDSA key fingerprint is SHA256:S9ESYzoNs9dv/i/6T0aqXQoSXHM.
Are you sure you want to continue connecting (yes/no)?
I want to automate the response "yes" to the above ssh command. How can I do that from the bash script ?
IP2 is a random IP so I cannot add it to the known hosts list on host IP1.
If you don't want to verify/check the fingerprint you could use something like:
ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no ubuntu#IP2 "ls -l ~"
This is how it works:
-o UserKnownHostsFile=/dev/null
The UserKnownHostsFile parameter specifies the database file to use for storing the user host keys (default is ~/.ssh/known_hosts).
By configuring the null device file as the host key database, SSH is fooled into thinking that the SSH client has never connected to any SSH server before, and so will never run into a mismatched host key.
-o StrictHostKeyChecking=no
The parameter StrictHostKeyChecking specifies if SSH will automatically add new host keys to the host key database file. By setting it to no, the host key is automatically added, without user confirmation, for all first-time connection.
For more details: How to disable SSH host key checking
Have you tested "StrictHostKeyChecking" option:
ssh -o "StrictHostKeyChecking no" root#10.x.x.x
I wonder if there is a way for me to SCP the file from remote2 host directly from my local machine by going through a remote1 host.
The networks only allow connections to remote2 host from remote1 host. Also, neither remote1 host nor remote2 host can scp to my local machine.
Is there something like:
scp user1#remote1:user2#remote2:file .
First window: ssh remote1, then scp remot2:file ..
Second shell: scp remote1:file .
First window: rm file; logout
I could write a script to do all these steps, but if there is a direct way, I would rather use it.
Thanks.
EDIT: I am thinking something like opening SSH tunnels but i'm confused on what value to put where.
At the moment, to access remote1, i have the following in $HOME/.ssh/config on my local machine.
Host remote1
User user1
Hostname localhost
Port 45678
Once on remote1, to access remote2, it's the standard local DNS and port 22. What should I put on remote1 and/or change on localhost?
I don't know of any way to copy the file directly in one single command, but if you can concede to running an SSH instance in the background to just keep a port forwarding tunnel open, then you could copy the file in one command.
Like this:
# First, open the tunnel
ssh -L 1234:remote2:22 -p 45678 user1#remote1
# Then, use the tunnel to copy the file directly from remote2
scp -P 1234 user2#localhost:file .
Note that you connect as user2#localhost in the actual scp command, because it is on port 1234 on localhost that the first ssh instance is listening to forward connections to remote2. Note also that you don't need to run the first command for every subsequent file copy; you can simply leave it running.
Double ssh
Even in your complex case, you can handle file transfer using a single command line, simply with ssh ;-)
And this is useful if remote1 cannot connect to localhost:
ssh user1#remote1 'ssh user2#remote2 "cat file"' > file
tar
But you loose file properties (ownership, permissions...).
However, tar is your friend to keep these file properties:
ssh user1#remote1 'ssh user2#remote2 "cd path2; tar c file"' | tar x
You can also compress to reduce network bandwidth:
ssh user1#remote1 'ssh user2#remote2 "cd path2; tar cj file"' | tar xj
And tar also allows you transferring a recursive directory through basic ssh:
ssh user1#remote1 'ssh user2#remote2 "cd path2; tar cj ."' | tar xj
ionice
If the file is huge and you do not want to disturb other important network applications, you may miss network throughput limitation provided by scp and rsync tools (e.g. scp -l 1024 user#remote:file does not use more than 1 Mbits/second).
But, a workaround is using ionice to keep a single command line:
ionice -c2 -n7 ssh u1#remote1 'ionice -c2 -n7 ssh u2#remote2 "cat file"' > file
Note: ionice may not be available on old distributions.
This will do the trick:
scp -o 'Host remote2' -o 'ProxyCommand ssh user#remote1 nc %h %p' \
user#remote2:path/to/file .
To SCP the file from the host remote2 directly, add the two options (Host and ProxyCommand) to your ~/.ssh/config file (see also this answer on superuser). Then you can run:
scp user#remote2:path/to/file .
from your local machine without having to think about remote1.
With openssh version 7.3 and up it is easy. Use ProxyJump option in the config file.
# Add to ~/.ssh/config
Host bastion
Hostname bastion.client.com
User userForBastion
IdentityFile ~/.ssh/bastion.pem
Host appMachine
Hostname appMachine.internal.com
User bastion
ProxyJump bastion # openssh 7.3 version new feature ProxyJump
IdentityFile ~/.ssh/appMachine.pem. #no need to copy pem file to bastion host
Commands to run to login or copy
ssh appMachine # no need to specify any tunnel.
scp helloWorld.txt appMachine:. # copy without intermediate jumphost/bastion host copy.**
ofcourse you can specify bastion Jump host using option "-J" to ssh command, if not configured in config file.
Note scp does not seems to support "-J" flag as of now. (i could not find in man pages. However above scp works with config file setting)
There is a new option in scp that add recently for exactly this same job that is very convenient, it is -3.
TL;DR For the current host that has authentication already set up in ssh config files, just do:
scp -3 remote1:file remote2:file
Your scp must be from recent versions.
All other mentioned technique requires you to set up authentication from remote1 to remote2 or vice versa, which not always is a good idea.
Argument -3 means you want to move files from two remote hosts by using current host as intermediary, and this host actually does the authentication to both remote hosts, so they don't have to have access to each other.
You just have to setup authentication in ssh config files, which is fairly easy and well documented, and then just run the command in TL;DR
The source for this answer is https://superuser.com/a/686527/713762
This configuration works nice for me:
Host jump
User username
Hostname jumphost.yourorg.intranet
Host production
User username
Hostname production.yourorg.intranet
ProxyCommand ssh -q -W %h:%p jump
Then the command
scp myfile production:~
Copies myfile to production machine.
a simpler way:
scp -o 'ProxyJump your.jump.host' /local/dir/myfile.txt remote.internal.host:/remote/dir
Is there a way I can create a alias for this command and have it ask for the host.
ssh -i .ssh/name.pem root#
Thx
Something like the following should work (not tested)
sshfunction(){
echo "Specify your hostname:"
read host
ssh -i .ssh/name.pem root#"$host"
}
Then:
$ sshfunction
Though if it was me, I'd just provide the hostname as a variable and cut-out the middle man.
Better yet, populate your ~/.ssh/config file (if it doesn't exist you can just create it):
host MyHostName
Hostname 123.456.7.89
User username
Then:
$ ssh MyHostName
I am writing an SSH config file and want to perform a bit of logic. For example:
Host myhost1
ProxyCommand ssh -A {choose randomly between [bastion_host1] and [bastion_host2]} -W %h:%p
Is it possible to achieve the above using (bash?) variables? Thanks!
Your ProxyCommand can be a shell script.
host myhost1
ProxyCommand $HOME/bin/selecthost %h %p
And then in ~/bin/selecthost:
#!/usr/bin/env bash
hosts=(bastion1 bastion2)
onehost=${hosts[$RANDOM % ${#hosts[#]}]}
ssh -x -a -q ${2:+-W $1:$2} $onehost
Untested. Your mileage may vary. May contain nuts.
Per comments, I've also tested the following, and it works nicely:
host myhost1 myhost2
ProxyCommand bash -c 'hosts=(bastion1 bastion2); ssh -xaqW%h:22 ${hosts[$RANDOM % ${#hosts[#]}]}'
Of course, this method doesn't allow you to specify a custom port per host. You could add that to the logic of a separate shell script if your SSH config matches multiple hosts in the same host entry.
In ~/.ssh/config you cannot have much logic, and no Bash. The manual for this file is in man ssh_config, and it makes no mention of such feature.
What you can do is create a script that will have the logic you need, and make you ssh configuration call that script.
Something along the lines of:
ProxyCommand sudo /root/bin/ssh-randomly.sh [bastion_host1] [bastion_host2]
And write a Bash script /root/bin/ssh-randomly.sh to take two hostname parameters, select one of them randomly, and run the real ssh command with the appropriate parameters.
No; .ssh/config is not processed by any outside program. You'll need a shell function along the lines of
ssh () {
(( $RANDOM % 2 )) && bastion=bastion_host1 || bastion=bastion_host2
command ssh -A "$bastion" "$#"
}
This can be handled within ssh config by using a helper app. For example,
Host myhost match exec "randprog"
hostname host1
Host myhost
hostname host2
and then randprog will randomly return 1 or 0 (0 will match the first line, giving host1).
The scenario is like:
SERVER_A="servera.com"
SERVER_A_UNAME="usera"
SERVER_B="serverb.com"
SERVER_B_UNAME="userb"
I want to write a shell script which will fist connect to server A, and then only it would be connected to server B. Like:
#!/bin/sh
ssh $SERVER_A_UNAME#$SERVER_A ...and then
ssh $SERVER_B_UNAME#$SERVER_B
But I am not able to do it. It does connect to server A only. How can I achieve it?
You may be able to find some help with this previous question:
How to use bash/expect to check if an SSH login works
Depending on your situation you might also to execute an remote ssh command and wait for positive feedback.
See:
How to use SSH to run a shell script on a remote machine?
you should have a look at ssh ProxyCommands that lets you do indirect connects automatically. basically you put the following in you .ssh/config
Host gateway1
# nichts
Host gateway2
ProxyCommand ssh -q gateway1 nc -q0 gateway2 22
Host targethost
ProxyCommand ssh -q gateway2 nc -q0 targethost 22
and then you can run ssh targethost successfully even if targethost is not reachable directly. you can read more about this e.g. here http://sshmenu.sourceforge.net/articles/transparent-mulithop.html