SSH (Secure SHell) is a protocol for running commands on a remote computer.

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2
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How can I ssh to a remote server with an automated password and no key?

I have a remote server. I planned to use public keys to connect over ssh without typing the password but the remote system rejects public key authentication. So what is the best way to do it? What ...
72
votes
4answers
72k views

What do the options `ServerAliveInterval` and `ClientAliveInterval` in sshd_config do, precisely?

I found this question, but I'm sorry I don't quite understand the settings on the two variables ServerAliveInterval and ClientAliveInterval mentioned in the accepted response. If my local server is ...
44
votes
3answers
20k views

How can I break away from an SSH session that has crashed?

Many times I have an SSH session that doesn't respond anymore (for example, when I lose internet connection and then reconnect). Ctrl+C, Ctrl+D, Ctrl+Z and a zillion of key presses don't have any ...
39
votes
5answers
47k views

Using while loop to ssh to multiple servers

I have a file servers.txt, with list of servers: server1.mydomain.com server2.mydomain.com server3.mydomain.com when I read the file line by line with while and echo each line, all works as ...
30
votes
3answers
39k views

SSH inside SSH fails with “stdin: is not a tty”

I'm trying to connect to machine one with ssh and then connect to another machine two with ssh, but I get this error. ssh user@computerone.com 'ssh otheruser@computertwo.com' stdin: is not a tty ...
39
votes
1answer
45k views

How does tcp-keepalive work in ssh?

I am trying to code a shell-script that uses a ssh-connection for doing "heartbeats". I want to terminate the client- and server-side of that connection after a certain timeout (after the connection ...
30
votes
4answers
113k views

ssh_exchange_identification: Connection closed by remote host (not using hosts.deny)

I'm not using hosts.allow or hosts.deny, further more SSH works from my windows-machine (same laptop, different hard drive) but not my Linux machine. ssh -vvv root@host -p port gives: OpenSSH_6.6, ...
18
votes
4answers
19k views

Is it possible to set Gnome Terminal's title to “user@host” for whatever host I'm connected to?

I'd like to set the terminal title to user@host so I can easily tell which machine I'm connected to from the window title. Is there a way to do this from SSH or from GNOME Terminal?
13
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3answers
9k views

How to execute a remote command and pass in local file as input?

Is it possible to do this: ssh user@socket command /path/to/file/on/local/machine That is to say, I want to execute a remote command using a local file in one step, without first using scp to copy ...
20
votes
5answers
4k views

Why is Firefox so slow over SSH?

I try to launch Firefox over SSH, using ssh -X user@hostname and then firefox -no-remote but it's very very slow. How can I fix this? Is it a connection problem?
8
votes
1answer
4k views

SSH over Socks proxy without username or password

I have a list of SOCKS proxy servers from this site. I've read about creating a dynamic tunnels with ssh -D and to be honest i've tried that already. Unfortunately for some reason I cannot connect to ...
26
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4answers
12k views

How can I determine if someone's SSH key contains an empty passphrase?

Some of my Linux & FreeBSD systems have dozens of users. Staff will use these "ssh gateway" nodes to SSH into other internal servers. We're concerned that some of these people use an unencrypted ...
18
votes
4answers
12k views

What's the difference between SFTP, SCP and FISH protocols?

I used to think SCP is a tool to copy files over SSH, and copying files over SSH is called SFTP, which is itself a synonym to FISH. But now as I was looking for a Total Commander plugin to do this in ...
11
votes
1answer
4k views

How to use ssh-agent with multiple (valid) keys and yet choose which one to use?

Let's say there are two keys A and B, both of which are valid for user@host public key authentication. Since authorized_keys is configured for different behaviour depending on the key, ~/.ssh/config ...
11
votes
3answers
2k views

Adding a user who can only execute scripts remotely

I would like to create a user who can only do one thing: via ssh specify a script ( and commandline arguments to the script ) that resides in one particular folder ( for the purposes of this question ...
12
votes
1answer
715 views

How to execute an arbitrary simple command over ssh without knowing the login shell of the remote user?

ssh has an annoying feature in that when you run: ssh user@host cmd and "here's" "one arg" Instead of running that cmd with its arguments on host, it concatenates that cmd and arguments with spaces ...
6
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3answers
2k views

Keep running a script via ssh

ssh can use to run remote commands. ssh me@server.com 'long-script.sh' I run a long script that will take a lot of time, but I want to close my computer and keep running the script in the remote ...
10
votes
2answers
7k views

dot file not sourced when running a command via ssh

When I run my program interactively, it works fine: ssh somehost $ ~/some/path/somescript.py When I run my program over ssh directly, it doesn't work. The variable PYTHONPATH is not set, because ...
9
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3answers
25k views

ssh, start a specific shell, and run a command on the remote machine?

I am in a situation where several users are sharing the same user account on a remote machine. I have a "personal" directory where I wrote my own .zshrc file, and I would like to have a way to: ...
7
votes
1answer
11k views

X11 forwarding an OpenGL application from a machine running an NVIDIA card to a machine with an AMD card

I'm interested in forwarding an X11 session over SSH, in order to launch a remote process that utilizes OpenGL (specifically, gazebo for anyone familiar.) The problem that I seem to be running into ...
5
votes
2answers
359 views

Why are rules not combining in an ssh config file?

It seems like the following would work as expected, i.e., that the second rule, having a hostname that matches the first rule, would apply it. Host *.hostname.com User myuser IdentityFile ...
7
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2answers
5k views

How can I set up SSH on Linux to log in password-less?

My Raspberry Pi is running the default Debian image and has SSH enabled. I log into my Pi as follows: ssh pi@<IP-address-of-my-Pi> I have to enter my password every time. Can I somehow make ...
7
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4answers
3k views

How to debug SSH port forwarding

This is an extension to ssh port forward to access my home machine from anywhere I tried things mentioned there but I am not able to ssh to my machine. Netgear router settings for port forwarding: ...
1
vote
1answer
1k views

SFTP over reverse SSH tunnel?

I want to SFTP to a remote computer that is behind NAT. I can't modify the NAT router, so I have set up a reverse SSH tunnel using a middleman server. Here's what my SSH tunnel looks like: ...
11
votes
3answers
18k views

Why does my X11 forwarding attempt fail with “connect /tmp/.X11-unix/X0: No such file or directory”?

On my local machine, I run: ssh -X me@remotemachine.com (For completeness, I have also tested all of the following using -Y with identical results). As expected, this accesses remotemachine.com ...
5
votes
1answer
385 views

Automated ssh login with passphrase?

Logging onto a machine over ssh typically requires a password to be entered before access is granted. Alternatively, a key/certificate (without a passphrase) can be installed onto the remote machine ...
3
votes
1answer
3k views

ssh into an account which has no home directory

As a follow up to my previous question, I have decided to create the local user accounts as below. adduser --system --no-create-home USERNAME Now, I would like the local users to be able to access ...
3
votes
1answer
918 views

Route SSH to host through interface

Is it possible to route all outgoing requests for SSH (port 22) to mydynamicdns.afraid.org via wlan0 instead of eth0 when both are connected? Since my IP is dynamic, I would like to use a name ...
2
votes
1answer
470 views

SSH Connection into LAN without port forwarding?

I'm living inside a study union for the next few month. the organisation has its own network and gateways where the students are connected to the internet. problem: I don't have access to the routers ...
101
votes
3answers
111k views

Why do I need a tty to run sudo if I can sudo without a password?

I have configured sudo to run without a password, but when I try to ssh 'sudo Foo", I still get sudo: sorry, you must have a tty to run sudo. Why does this happen and how can I work around it?
61
votes
3answers
45k views

how can shellshock be exploited over SSH?

Apparently, the shellshock Bash exploit CVE-2014-6271 can be exploited over the network via SSH. I can imagine how the exploit would work via Apache/CGI, but I cannot imagine how that would work over ...
50
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4answers
11k views

Why is root login via SSH so bad that everyone advises to disable it?

Everybody on the Internet advises to disable root login via SSH as it is a bad practice and a security hole in the system, but nobody explains why it is so. What is so dangerous in enabling root ...
47
votes
2answers
117k views

List all connected SSH sessions?

I just SSH'd into root, and then SSH'd again into root on the same machine. So I have two windows open both SSH'd into root on my remote machine. From the shell, how can I see a list of these two ...
12
votes
4answers
9k views

Autocomplete server names for SSH and SCP

I have a few servers configured in ~/.ssh/config, such as alpha and beta. How might I configure Bash such that the commands ssh al<tab> and scp file.tgz al<tab> autocomplete the names of ...
46
votes
5answers
34k views

How can I tell what version of Linux I'm using?

Often times I will ssh into a new client's box to make changes to their website configuration without knowing much about the server configuration. I have seen a few ways to get information about the ...
18
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3answers
24k views

What difference between openssh key and putty key?

I've found that ssh-keygen ("ssh" package) produces different keys from puttygen ("putty" package). If I create public and private keys with ssh-keygen some ssh-servers will not accept my keys. If I ...
20
votes
3answers
10k views

How do I know if my ssh tunnel is created successfully?

I rely on the following script tunnel.sh written by others to keep a ssh tunnel alive: #!/bin/bash export SSH_HOST=tim@server if [ ! -f /tmp/.tunnel ] then echo "Creat SSH tunnel" ssh -f -D 9999 ...
20
votes
3answers
21k views

Tell SSH to use a graphical prompt for key passphrase

How can I force SSH to request passphrases using a graphical prompt (GTK, for example) instead of the standard one that uses the terminal? I tried setting SSH_ASKPASS=/usr/bin/ssh-askpass but it ...
32
votes
7answers
16k views

Can I find out which ssh key was used to access an account?

Is it possible to find out which ssh key was used to access an account? I have an account on a server that I let several (trusted!) people have access to via ssh. I'd find it useful to be able to ...
8
votes
2answers
5k views

How can I make ssh ignore .ssh/config?

I have the following in my ~/.ssh/config. HOST 10.2.192.* USER foo PreferredAuthentications publickey IdentityFile ~/.ssh/foo/id_rsa The above configuration lets me connect ...
23
votes
2answers
4k views

SSH output isn't line buffered?

I'm running a script on a remote machine like this: ssh $host "pip install -r /path/to/requirements.txt" But the output isn't line buffered; instead of seeing one line returned at a time, all the ...
20
votes
2answers
2k views

Why is this binary file transfered over “ssh -t” being changed?

I am trying to copy files over SSH, but cannot use scp due to not knowing the exact filename that I need. Although small binary files and text files transfer fine, large binary files get altered. Here ...
13
votes
3answers
13k views

Differences between VNC and ssh -X

Why would you use VNC (or for that matter NX) instead of just using ssh -X (-Y). I read that VNC uses less bandwidth, but is there any other differences/advantages with respective tool?
12
votes
3answers
8k views

Get ssh server key fingerprint

Is there a way to programmatically obtain a SSH server key fingerprint without authenticating to it? I'm trying ssh -v user@host false 2>&1 | grep "Server host key", but this hangs waiting for ...
11
votes
2answers
3k views

Detach/reattach an application run on X over SSH?

I have a development server that I leave running all the time, and a development laptop that I turn off/on everyday. I have a GUI application on the server that I'd like to run over SSH -X, and I'd ...
6
votes
4answers
28k views

Pseudo-terminal will not be allocated because stdin is not a terminal

I'm trying to set up automatic SSH hopping through a server which doesn't have nc. This works from the command line: ssh -A gateway ssh steve@target (I have added my public key to the SSH agent). ...
13
votes
3answers
22k views

ssh remote server on some port other than 22 without password

I am usually connecting to the remote server with ssh user@server.com -p 11000 and then giving the password each time for user. How should I avoid entering the password each time I connect ...
8
votes
1answer
1k views

Can I move a running application to a different X server?

Is there any way to open a graphical program (for instance, gedit) while using X11 forwarding over SSH and transfer the X server connection back to the X server on the SSH host?
7
votes
4answers
24k views

Set some firewall ports to only accept local network connections?

Basic firewall question: How do I set up the firewall on a system in a LAN so that some ports are only open to connections from the local area network, and not from the outside world? For instance, ...
5
votes
1answer
5k views

Compress a directory using tar/gz over SSH to local computer?

I'd like to essentially tar/gz a directory on a remote machine and save the file to my local computer without having to connect back into my local machine from the remote one. Is there a way to do ...