Secure Shell (SSH) is a protocol primarily for encrypted shell connections. This tag is also used for questions about sshd and openssh, the two standard applications for using SSH.

learn more… | top users | synonyms (2)

68
votes
15answers
12k views

Hundreds of failed ssh logins

Every night I get hundreds, sometimes thousands, of failed ssh logins on my RedHat 4 server. For firewall reasons from remote sites, I need to run on the standard port. Is there anything I should be ...
18
votes
6answers
10k views

Is there a name based virtual host SSH reverse proxy?

I've grown quite fond of HTTP reverse proxies in our development environment and found the DNS based virtual host reverse proxy quite useful. Having only one port (and the standard one) open on the ...
17
votes
6answers
22k views

Cygwin SSHd Autoblock Failed Logins

I'm running Cygwin with an SSH deamon on a Windows Server 2008 machine. I was looking at the Event Viewer and noticed as much as 5 to 6 failed login attempts per second (brute force) for the last week ...
196
votes
22answers
57k views

Is it normal to get hundreds of break-in attempts per day?

I just checked my server's /var/log/auth.log and found that I'm getting over 500 failed password/break-in attempt notifications per day! My site is small, and its URL is obscure. Is this normal? ...
211
votes
11answers
67k views

Can I nohup/screen an already-started process?

I'm doing some test-runs of long-running data migration scripts, over SSH. Let's say I start running a script around 4 PM; now, 6 PM rolls around, and I'm cursing myself for not doing this all in ...
113
votes
9answers
219k views

What is a good SSH server to use on Windows? [closed]

In my spare time I remotely support my wife's office via VPN into a Windows Server. I am about to purchase a wireless broadband service which doesn't support VPN. I don't want to open up the remote ...
64
votes
2answers
91k views

SFTP logging: is there a way?

I'm wondering if there is a way to log commands received by the server. It can be all SSH commands, as long as it includes information on commands related to file transfer. I'm having issues with an ...
26
votes
8answers
22k views

A system for distributing SSH public keys

We have many different systems that are managed by several people. We have chosen to use SSH public key authentication to access those systems. This works great, as there is no need to manage or share ...
41
votes
14answers
6k views

Preventing brute force attacks against ssh?

What tool or technique do you use to prevent brute force attacks against your ssh port. I noticed in my Security logs, that I have millions of attempts to login as various users through ssh. This is ...
27
votes
8answers
8k views

How do you setup ssh to authenticate using keys instead of a username / password?

How do you setup ssh to authenticate a user using keys instead of a username / password?
33
votes
5answers
4k views

Smoothest workflow to handle SSH host verification errors?

This is a simple issue that we all face and probably resolve manually without giving much thought. As servers change, are re-provisioned, or IP addresses reallocated, we receive the SSH host ...
18
votes
5answers
13k views

How can I chroot ssh connections?

I would like to setup a chroot jail for most (not all) users logging in though SSH. I've heard it's possible with the latest versions of openssh, but I've not been able to find out how to do it. The ...
19
votes
2answers
2k views

Do the SSH or FTP protocols tell the server to which domain I am trying to connect?

When using the ssh or ftp commands from the Bash shell, does the server that I am connecting to learn of the domain name used? I understand that the domain name is locally translated into an IP ...
3
votes
4answers
967 views

ssh delay when connecting

When connecting to one specific server (running Debian Lenny) it always takes about 5 seconds before it prompts me to enter a password. After login there is no noticable delay anymore. There is also ...
73
votes
14answers
5k views

What's wrong with always being root?

I have a feeling this is a stupid question, but this is something I've wondered for awhile. I have a VPS and this is my first big linux venture. I am the only person who has access to it. My question ...
166
votes
6answers
372k views

How to automate SSH login with password?

How to automate SSH login with password? I'm configuring my test VM, so heavy security is not considered. SSH chosen for acceptable security with minimal configuration. ex) echo password | ssh id@...
125
votes
9answers
72k views

Keeping a linux process running after I logout

I'm connecting to a Linux machine through SSH, and I'm trying to run a heavy bash script that makes filesystem operations. It's expected to keep running for hours, but I cannot leave the SSH session ...
28
votes
8answers
35k views

How to setup ssh's umask for all type of connections

I've been searching for a way to setup OpenSSH's umask to 0027 in a consistent way across all connection types. By connection types I'm referring to: sftp scp ssh hostname ssh hostname program ...
44
votes
3answers
15k views

Does getting disconnected from an SSH session kill your programs?

So, say I get disconnected from an SSH-session after I've started rsync or cp or any other command that can be long running. Does that command keep running until it's finished after I get disconnected ...
10
votes
5answers
5k views

Is it worth the effort to block failed login attempts

Is it worthwhile running fail2ban, sshdfilter or similar tools, which blacklist IP addresses which attempt and fail to login? I've seen it argued that this is security theatre on a "properly secured"...
11
votes
6answers
3k views

Does disabling root login enhance security?

I have recently found an argument against disabling a root user login in Linux at http://archives.neohapsis.com/archives/openbsd/2005-03/2878.html I assume that, if everybody uses a public key ...
110
votes
7answers
130k views

Can I automatically add a new host to known_hosts?

Here's my situation: I'm setting up a test harness that will, from a central client, launch a number of virtual machine instances and then execute commands on them via ssh. The virtual machines will ...
20
votes
7answers
9k views

How to configure a shortcut for an SSH connection through a SSH tunnel

My company production servers (FOO, BAR...) are located behind two gateway servers (A, B). In order to connect to server FOO, I have to open a ssh connection with server A or B with my username ...
4
votes
4answers
1k views

How to restore remote access to a RHEL system from expanded permissions set over the entire filesystem? [duplicate]

Cause of the problem I intended to add group write permission on hidden files like '.hgignore' with the following: # pwd /opt # sudo chmod -R g+w .* The problem is that '..' matched this pattern, ...
1
vote
5answers
6k views

SSH key exchange is not working

Is there any way to verify why SSH key exchange between 2 servers is not working? In Server A: I did the following steps: ssh-keygen –t rsa cd /.ssh cp id_rsa.pub authorized_keys Then in Server B:...
96
votes
10answers
40k views

ssh-agent forwarding and sudo to another user

If I have a server A into which I can login with my ssh key and I have the ability to "sudo su - otheruser", I lose key forwarding, because the env variables are removed and the socket is only ...
96
votes
14answers
117k views

How to reconnect to a disconnected ssh session

Is there a way to connect to an ssh session that was disconnected? We are having problems with our network connection to a remote site that we are working on separately; however, in the mean time we ...
93
votes
6answers
31k views

SSH keypair generation: RSA or DSA?

SSH supports two signature algorithms for key pairs: RSA and DSA. Which is preferred, if any? For RSA, what is the minimum acceptable key length?
112
votes
4answers
52k views

What's the difference between authorized_keys and authorized_keys2?

Just wanted a quick summary of the differences between them and why there are two? Cheers
17
votes
5answers
39k views

How to put desired umask with SFTP?

I have a SFTP server (openssh/sftp-server) and I would like to set umask 002 for users using this service. I tried setting PAM (pam.d/common-session), and .profile for each user, but no luck. With ...
11
votes
9answers
2k views

SSH to a computer that will then SSH to another computer [duplicate]

Possible Duplicate: How to configure a shortcut for an SSH connection through a SSH tunnel I have a situation where I would like to have SSH/SFTP access from my workstation to a server that is ...
10
votes
12answers
2k views

Securing SSH server against bruteforcing

I have a little SVN server, old dell optiplex running debian. I don't have that high demands on my server, because its just a little SVN server... but do want it to be secure. I just renewed my ...
7
votes
4answers
8k views

SSH relay server with OpenSSH

Is it possible to use OpenSSH to relay to other SSH enabled devices such as routers switches etc.. If is this something that can be done without creating a bespoke application on Linux to do it? ...
35
votes
5answers
44k views

Is it possible to use rsync over sftp (without an ssh shell)?

Rsync over ssh, works great every time. However, trying to rsync to a host which allows only sftp logins, but not ssh logins, provides the following error: rsync -av /source ssh user@remotehost:/...
10
votes
9answers
33k views

Amazon EC2 - No SSH After Reboot, Connection Refused

I've replicated this two or three times, so I'm guessing there's something wrong with what I'm doing. Here are my steps: Launch new instance via EC2 Management console using: Ubuntu Server 13.10 - ...
12
votes
6answers
42k views

SSH issues: Read from socket failed: Connection reset by peer

I compiled OpenSSH_6.6p1 on one of our server. I am able login via SSH to the upgraded server. But I am not able to connect to other servers running OpenSSH_6.6p1 or OpenSSH_5.8 from this. While ...
8
votes
2answers
1k views

SSH port forwarding

I want to connect to my computer(local) behind NAT through a public accessible server(public). On local: ssh -g -R 8000:localhost:22 user@public Then on public: ssh -p 8000 user@public But I ...
7
votes
1answer
6k views

Does OpenSSH SFTP server use umask or preserve client side permissions after put command (chrooted environment)?

I know this question has been already discussed, but by reading the posts I could not figure the answers, because some said "yes umask can work", and others say "OpenSSH put command always preserve ...
3
votes
1answer
2k views

SFTP user can't edit or create files

Server: Ubuntu 12.04 LTS I am using openSSH and have created an SFTP user called bob who belongs to group sftponly. I have chrooted bob to his home directory which is /usr/share/nginx/www/bob/. bob ...
2
votes
1answer
239 views

fatal: bad ownership or modes for chroot directory component “/” in SFTP

I've been trying to configure sftp in a debian server.sshd_config: Subsystem sftp internal-sftp UsePAM no Match User sftpUser ChrootDirectory /users/sftp/sftpUser ForceCommand internal-sftp ...
-1
votes
4answers
4k views

Dump all databases with SSH access

I would like to know how to dump all databases into a folder. I'm using a Linux/Debian Afer connecting on the server with root access I make $ mysql -u admin -p To connect on mysql. Then which ...
10
votes
3answers
2k views

How to tell if a public SSH key has a passphrase

This is probably a noob question, but how can I determine if the public SSH key someone gives me has a passphrase or not? We have a situation where I am not generating the SSH keys for users, but I ...
169
votes
15answers
457k views

Why do I get “Permission denied (publickey)” when trying to SSH from local Ubuntu to a Amazon EC2 server?

I have an instance of an application running in the cloud on Amazon EC2 instance, and I need to connect it from my local Ubuntu. It works fine on one of local ubuntu and also laptop. I got message "...
34
votes
5answers
10k views

Best system for managing ssh keys? [closed]

I've got several client computers (i.e. laptops, desktops, etc.), and I connect to several server machines that I manage, and I log into them all via SSH. I can imagine several schemes of managing ...
27
votes
2answers
23k views

SSH key authentication using LDAP

In short: Would like a way to do SSH key authentication via LDAP. Problem: We use LDAP (slapd) for directory services and we've recently moved to using our own AMI for building instances. The ...
24
votes
8answers
22k views

What is a good modern parallel SSH tool? [duplicate]

I have heard that pssh and clusterssh are two popular ones, but I thought I would open it to discussion here and see what the community's experiences with these tools were? What are the gotchas? Any ...
44
votes
6answers
24k views

How do I do Multihop SCP transfers?

I want to copy a file from my machine A to server C, but only have access to server C through server B. Instead of first transferring to server B, log in and then transfer to server C, Is is possible ...
24
votes
4answers
8k views

How do I sudo over sshfs?

On my local host alpha I have a directory foo that is mapped via sshfs to host bravo as follows: $ sshfs charlie@bravo:/home/charlie ~/foo However, on host bravo there is another user, delta, that ...
10
votes
4answers
10k views

How can I create a user only for sftp?

I have added a user to the system via the adduser tool. Then, in /etc/passwd, I tried changing the /bin/bash to /sbin/nologin or to /dev/null, but neither of these worked. I would like the user not ...
5
votes
3answers
4k views

How do I setup ssh with both private key and password?

How do I setup ssh with both private key and password? In /etc/ssh/sshd_config, I currently have: RSAAuthentication yes PubkeyAuthentication yes PasswordAuthentication yes But apparently this ...