OpenSSH is one of the most popular implementations of SSH used today and available by default in many Linux and Unix-like operating systems.

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75
votes
9answers
172k views

Remove key from known_hosts

I built several virtual machines during the last few weeks. The problem is, the .ssh/known_hosts gives me the Man in the middle warning. This happens because another fingerprint is associated with the ...
61
votes
4answers
44k views

How to make ssh tunnel open to public?

Well, referring back to this question, I am running the command ssh -R 8080:localhost:80 -N root@example.com on a Mac. Yet the port that is being tunneled is not working publicly. I am running such ...
54
votes
7answers
18k views

Is there a way for one SSH config file to include another one?

In case it matters: OS: Ubuntu 10.04 SSH: OpenSSH_5.3p1 Debian-3ubuntu5 I'd like one SSH config file to include another one. The use case would be to define whatever I want in my default .ssh/...
42
votes
3answers
9k views

SHA256 ssh fingerprint given by the client but only md5 fingerprint known for server

When connecting to a new/unknown server (with recent OpenSSH) like: ssh example.com You get the fingerprint like that: The authenticity of host 'example.org (192.0.2.42)' can't be established. RSA ...
21
votes
9answers
38k views

Why does the “password” prompt take forever when I SSH into my Ubuntu 9.05 server?

Answer: It was, in fact, performing reverse DNS resolution. Based on the suggestions below and this article, I added "UseDNS no" to my sshd_config, rebooted ssh, and now the password prompt displays ...
20
votes
1answer
8k views

Does the right half of the rsa public key matter?

In a public key file "id_rsa.pub" generated by ssh-keygen, does the part after the == matter? I ask because when I changed "root@somedomain.com" to "root", it seems to still work. More generally, I ...
20
votes
4answers
5k views

how to disable SendEnv variables set in ssh_config from ~/.ssh/config

I couldn't find that anywhere so I'm wondering am I the only one hitting such issue. By default ssh on Red Hat and Debian at least has a ssh_config with SendEnv option passing LC* and LANG variables ...
17
votes
1answer
19k views

What does “key_load_public: no such file or directory” mean?

I've been troubleshooting a PubkeyAuthentication-only issue. When I use verbose mode, I see a lot of "key_load_public: no such file or directory". Obviously, the keys exits on the filesystem, so that ...
16
votes
3answers
116k views

SSH Permission denied on Correct Password Authentication

I could successfully SSH into my machine yesterday with the exact same credentials I am using today. The machine is running Centos 6.3. But now for some reason it is giving me permission denied. Here ...
13
votes
6answers
46k views

How to SSH to localhost without password?

EDIT: Putting exactly what was done. I need to SSH to localhost without a password, the usual way of doing it (with public keys) do not work. user@PC:~$ rm -rf .ssh/* user@PC:~$ ssh-keygen -t rsa &...
12
votes
9answers
27k views

How do I skip the “known_host” question the first time I connect to a machine via SSH with public/private keys? [duplicate]

How do I skip the "known_host" question the first time I connect to a machine via SSH with public/private keys?
12
votes
8answers
42k views

OpenSSH server refuses to accept key authentication

I tried to use public key authentication on my new server, and I came across this problem. $ ssh -v -i .ssh/server 192.168.1.100 OpenSSH_5.6p1, OpenSSL 0.9.8r 8 Feb 2011 debug1: Reading configuration ...
11
votes
3answers
35k views

How to uninstall/reinstall cygwin to use the sshd?

I installed cygwin/sshd without good results. I removed the c:\cygwin directory to reinstall. I removed the sshd Administrator user by hand. I reinstalled the cygwin again, then run the 'ssh-host-...
11
votes
7answers
14k views

How to edit known_hosts when several hosts share the same IP and DNS name?

I regularly ssh into a computer which is a dual-boot OS X / Linux computer. The two OS instance do not share the same host key, so they can be seen as two host sharing the same IP and DNS. Let's say ...
11
votes
3answers
7k views

SSH: completly disabling password authentication

is there a way to disable password authentication completely? The command line is the following: ssh -o KbdInteractiveAuthentication=no -o PasswordAuthentication=no machine" it STILL asks for a ...
11
votes
2answers
2k views

How to determine the port allocated on the server for a dynamically bound openssh reverse tunnel?

When creating reverse tunnels on recent versions of OpenSSH a remote port of 0 can be given to bind any available port: -R [bind_address:]port:host:hostport ... If the port argument is `...
10
votes
4answers
39k views

Can someone explain the 'PasswordAuthentication' in the /etc/ssh/sshd_config file?

On this page, the explanation given is: The option PasswordAuthentication specifies whether we should use password-based authentication. For strong security, this option must always be set ...
10
votes
2answers
11k views

git pull does nothing / git push just hangs / debug1: expecting SSH2_MSG_KEX_ECDH_REPLY

I had an issue in ubuntu 13.10 and 12.10 where attempting to connect to github (git clone / pull / push or anything) would fail with no output. I checked my /.ssh directory for config and any ssh ...
10
votes
3answers
10k views

ssh config under cygwin

I have Cygwin installed on Windows 7. I made default install. I would like to use ssh config file (~/.ssh/config) to set host and options for connecting. Normal ssh command is not able to find the ...
10
votes
1answer
9k views

PubkeyAcceptedKeyTypes and ssh-dsa key type

I'm trying to test the order in which keys are tried. One of the system's users is using DSA, so I'm trying to test it as an option. I'm getting a Bad key types. $ ssh -vv -p 1522 jwalton@192.168.1....
10
votes
1answer
5k views

How to add pointers to filesystems outside the chrooted environment - using chrooted SFTP via OpenSSH

So, I'm pretty sure this is true, but I haven't found a specifically detailed independent reference that directly answers my question. Question being: How can I add access to a resource that is ...
9
votes
4answers
3k views

Multiple SSH connections to the same system - is it possible?

I have a linux computer acting as a server which can accept incoming SSH connections. Is it possible to reliably connect multiple devices at the same time, such as my phone and laptop, as well as ...
9
votes
2answers
17k views

change default username when ssh to another pc [duplicate]

When I ssh between different pcs I can omit my username (tom) and just type ssh pc_name instead of ssh tom@pc_name I like this feature, and have got into the habit of using it. Unfortunately, ...
8
votes
1answer
9k views

How can I find a list of MACs, Ciphers, and KexAlgorithms that my openssh client supports?

Is there a way to make ssh output what MACs, Ciphers, and KexAlgorithms that it supports? I'd like to find out dynamically instead of having to look at the source.
8
votes
1answer
5k views

Can I change the filename of my ssh public/private key pair?

I created a public/private key pair: ssh-keygen -t rsa -C "me@example.com" I gave a different key file name than id_rsa since I wanted to create a new separate key from my normal identity. I gave ...
8
votes
1answer
4k views

Checking ssh keys have passphrases

I have a bunch of users, who with SSH keys have access to accounts on other servers. Currently I have a script which collects up the ssh public keys and distributes them to the correct account on the ...
8
votes
1answer
2k views

Is OpenSSH sending an email to no-more-sessions@openssh.com every time I connect?

When I try to connect to my EC2 (Ubuntu 14.04.3) server with ssh -v server, I see this at the end of the log: debug1: read PEM private key done: type RSA debug1: Authentication succeeded (publickey). ...
8
votes
1answer
3k views

OpenSSH ~/.ssh/config host-specific overrides not working

I've tried setting up my ~/.ssh/config file with the help of this guide. However, the host-specific User override has no effect and ssh tries to connect using the global username instead of the host-...
8
votes
1answer
8k views

Denyhosts keeps adding my IP address to hosts.deny

I have setup Denyhosts to run on my server, and have been using it succesfully for the last few weeks, to allow me to ssh into my server from my home dev machine. This morning, I accidentally typed ...
8
votes
1answer
29k views

How can I setup the openSSH SFTP server on Linux?

I want to configure sftp-server to share a directory but I don't know how to modify /etc/ssh/sshd_config. My requirements are: 1) Login shall not use certificates, only password (i.e. authorization ...
7
votes
2answers
3k views

How to make ssh log in as the right user?

I use ssh on a variety of machines, mainly linux. Accounts on these machines vary in naming scheme: if my name is First Last, then I have accounts: first, flast, last_f, lastf, and sometimes I need to ...
7
votes
1answer
3k views

ssh -o PreferredAuthentications: What's the difference between “password” and “keyboard-interactive”?

Both PreferredAuthentications=password and PreferredAuthentications=keyboard-interactive would prompt for the password, so what's the difference between them? I Google'd with the keywords ssh ...
7
votes
1answer
3k views

Nohup over ssh won't return

I am trying to do [me@myPc]$ ssh me@server "nohup myBashScript.sh &" My goal is to launch the process on the server, and then immediately return. It is not working: The job is started on ...
7
votes
1answer
2k views

SSHD Consuming 100% of CPU (Hundreds of processes) - Will not die

Recently I've noticed that SSHd on a few systems I administrate will start spawning unstoppable processes which will consume huge amounts of CPU. The syscall shows that the processes are all 'running'...
7
votes
4answers
5k views

Secure remote editing of root-accessible files over SSH

As per security best practices one should not allow root login over SSH with password or keys. Instead, sudo should be used. However, if one wants to use SSH (SFTP) for remote editing of server ...
6
votes
4answers
6k views

Configure OSX Firewall to Allow SSH Server?

If I turn on my OSX firewall, ssh is disallowed. If I turn it off, ssh can connect just fine. These are the settings from the ssh host: while I don't know what I'm doing, I figured that giving /usr/...
6
votes
3answers
14k views

One user can use SSHFS, other user gets “remote host has disconnected”

I have two users with valid SSH accounts on a server. Both users can login via ssh successfully. When trying to mount SSHFS, usera can mount with no problems, while userb gets the error: remote host ...
6
votes
1answer
808 views

How are Ciphers, MACs and Key exchange algorithms negotiated by OpenSSH?

Looking at the man page for sshd_config I see the default list of algorithms for Ciphers, Key Exchange (KEX) and MACs. In my set up, I have selected a subset of these algorithms for use (i.e. I don't ...
5
votes
2answers
1k views

How to stop adding IP from EC2 to known_hosts for ssh?

I start/stop lots of new instances as I'm learning to use Amazon EC2. Every temporary instance is added to the known_hosts file. Is this ever a problem for others who use EC2 a lot? I'd like to tell ...
5
votes
6answers
10k views

How to tunnel port 25565 through SSH?

I want to play a game which is hosted on port 25565 (minecraft!), but my university firewall does not allow this port. I have a dedicated server running linux not too far from uni, so I think there's ...
5
votes
2answers
5k views

1and1 ssh - connection refused

I'm having troubles connecting through SSH to my 1&1 account. When I try to connect with command userXXX@host -p22 -vv I have the following output: OpenSSH_5.8p1 Debian-7ubuntu1, OpenSSL 1.0....
5
votes
1answer
2k views

SSH DSA keys no longer work for password-less authentication

After upgrading to Fedora 23, passwordless (public-key-based) authentication no longer works in SSH: when trying to SSH to some host, it prompts for my password at the remote host. I can't get it to ...
5
votes
2answers
1k views

cygwin ssh shortcut on windows desktop

I have multiple servers that I need to remote into. I prefer Cygwin over Putty to do so. Anyhows - the process of opening my cool Mintty window and then typing the following commands takes too long. ...
5
votes
1answer
3k views

What is a GPG with “authenticate” capability used for?

GnuPG subkeys can be flagged with three kind of capabilities: Sign, Encrypt and Authenticate. While the first two actions are widely used and documented, the authenticate action is somehow mysterious....
4
votes
1answer
3k views

Can I access a remote web server over an SSH connection?

I recently set up a remote server, which I have running the bare minimums currently. I set up OpenSSH and can access the machine through one of my domain names (using an A-type DNS record). I also ...
4
votes
1answer
2k views

OpenSSH public key structure

Let's say that my username is user and my computername is cmp. I notice they are also part of my SSH public key: (they are last, scroll right) user@cmp:~/.ssh$ ls config id_rsa id_rsa.pub ...
4
votes
1answer
759 views

Howto force ssh to use a specific private key?

With ssh -i <private key filename> you can instruct ssh to use an extra private key to try authentication. The documentation is not clear on how to explicitly use only that key.
4
votes
4answers
9k views

Cygwin sshd did not start due to a logon failure

After a cygwin sshd install, sshd service fails with: Error 1069: The service did not start due to a logon failure I try to give cyg_server standard user and admin access. The error is the same ...
4
votes
1answer
2k views

Why would anyone install openssh-client instead of openssh-server? [closed]

I installed openssh-server on two pc's. I can connect from both from the one to the other. So if openssh-server sends as well as receives ssh, why would you install the openssh-client, just to make ...
4
votes
2answers
810 views

Automatically reconnect interactive SSH session

What's the best way to automatically reconnect an interactive SSH session to re-establish the shells on terminals? I looked at autossh but that seems to be dedicated to port forwards (which I do not ...