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

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237
votes
4answers
840k views

How to copy files from one machine to another using ssh [duplicate]

I'm using Linux (centos) machine, I already connected to the other system using ssh. Now my question is how can I copy files from one system to another system? Suppose, in my environment, I have two ...
183
votes
21answers
258k views

Why am I still getting a password prompt with ssh with public key authentication?

I'm working from the URL I found here: http://jaybyjayfresh.com/2009/02/04/logging-in-without-a-password-certificates-ssh/ My ssh client is Ubuntu 64 bit 11.10 desktop and my server is Centos 6.2 64 ...
165
votes
6answers
337k views

How to forward X over SSH from Ubuntu machine?

I have a machine running Ubuntu which I SSH to from my Fedora 14 machine. I want to forward X from the Ubuntu machine back to Fedora so I can run graphical programs remotely. Both machines are on a ...
160
votes
9answers
154k views

SSH easily copy file to local system

If I'm logged in to a system via SSH, is there a way to copy a file back to my local system without firing up another terminal or screen session and doing scp or something similar or without doing SSH ...
137
votes
5answers
150k 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?
131
votes
3answers
82k views

How does reverse SSH tunneling work?

As I understand this, firewalls (assuming default settings) deny all incoming traffic that has no prior corresponding outgoing traffic. Based on Reversing an ssh connection and SSH Tunneling Made ...
125
votes
7answers
78k views

Keep SSH Sessions running after disconnection

I sometimes have long running processes that I want to kick off before going home, so I create a SSH session to the server to start the process, but then I want to close my laptop and go home and ...
119
votes
6answers
67k views

How to force ssh client to use only password auth?

If I use pubkey auth from e.g.: an Ubuntu 11.04 how can I set the ssh client to use only password auth to a server? (just needed because of testing passwords on a server, where I default log in with ...
113
votes
8answers
63k views

How can I disown a running process and associate it to a new screen shell?

I have a running program on a SSH shell. I want to pause it and be able to unpause its execution when I come back. One way I thought of doing that was to transfer its ownership to a screen shell, ...
105
votes
9answers
119k views

How can I run ssh-add automatically, without password prompt?

I want to communicate between several computers on my network (static ethernet), through ssh. In order to do that I need to run ssh-add every time I login on specific machine, how can I do it so that ...
82
votes
5answers
86k 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 ...
80
votes
19answers
134k views

SSH tunneling error: “channel 1: open failed: administratively prohibited: open failed”

When I open this ssh tunnel: ssh -nXNT -p 22 localhost -L 0.0.0.0:8984:remote:8983 I get this error when trying to access the HTTP server running on localhost:8984: channel 1: open failed: ...
80
votes
8answers
120k views

ssh-add complains: Could not open a connection to your authentication agent

I've been trying to get ssh-add working on a RaspberryPi running Raspbian. I can start ssh-agent, when I do it gives the following output into the terminal: SSH_AUTH_SOCK=/tmp/ssh-06TcpPflMg58/...
75
votes
3answers
29k views

Multiple similar entries in ssh config

Say I want to configure my ssh options for 30 servers with the same setup in my .ssh config file: host XXX HostName XXX.YYY.com User my_username Compression yes Ciphers arcfour,...
73
votes
7answers
33k views

Is it possible to run ssh-copy-id on port other than 22?

I have a server with SSH running on a non-standard port. Instead of 22, it runs on 8129. To log in, I use: ssh -p 8129 hostname Now, whenever I need to set up a key for password-less login, I have ...
71
votes
6answers
71k views

scp without replacing existing files in the destination

How do I copy an entire directory into a directory of the same name without replacing the content in the destination directory? (instead, I would like to add to the contents of the destination folder)
65
votes
3answers
48k 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 ...
65
votes
3answers
157k 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 ...
62
votes
4answers
52k views

Is it possible to find out the hosts in the known_hosts file?

I would like to see what hosts are in my known_hosts file but it doesn't appear to be human readable. Is it possible to read it? More specifically there is a host that I can connect to via several ...
58
votes
1answer
48k views

How to list keys added to ssh-agent with ssh-add?

How and where can I check what keys have been added with ssh-add to my ssh-agent ?
58
votes
1answer
11k views

Kill an unresponsive ssh session without closing the terminal

Is there a way to disconnect from an SSH session that has become unresponsive without killing the whole terminal? Specifically I'm using konsole, and the machine I'm working with sometimes hangs, but ...
56
votes
5answers
47k views

What is the point of sshd “UseDNS” option?

I know what it does, but i don't know why. What attack(s) does it prevent ? Is it relevant for all kind of authentication methods ? (hostbased, password, publickey, keyboard-interactive ...)
56
votes
2answers
8k views

How does SSH connection survive a network restart?

From a Linux SSH shell, type /etc/init.d/network restart to restart the network service. I expect my SSH connection to die since the network service goes down. But it doesn't. Very cool. But how does ...
56
votes
7answers
74k views

What does the Broken pipe message mean in an SSH session?

Sometimes my SSH session disconnects with a Write failed: Broken pipe message. What does it mean? And how can I keep my session open? I know about screen, but that's not the answer I'm looking for. I ...
55
votes
4answers
14k 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 ...
53
votes
2answers
25k views

ssh-add is not persistent between reboots

I add a ssh key to the agent by $ ssh-add ~/.ssh/id_rsa_mac Identity added: /Users/alex/.ssh/id_rsa_mac (/Users/alex/.ssh/id_rsa_mac) After reboot I don't have this key added anymore: $ ssh-add -l ...
52
votes
7answers
81k views

Uploading directories with sftp?

I'm having some trouble uploading directories(which contain other directories a few levels deep) by sftp. I realize I could work around this by gzipping, but I don't see why that's necessary. Anyway, ...
52
votes
5answers
41k 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 ...
49
votes
4answers
85k views

Open a window on a remote X display (why “Cannot open display”)?

Once upon a time, DISPLAY=:0.0 totem /path/to/movie.avi after ssh 'ing into my desktop from my laptop would cause totem to play movie.avi on my desktop. Now it gives the error: No protocol ...
49
votes
3answers
22k 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 ...
46
votes
1answer
51k 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 ...
45
votes
6answers
63k 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 ...
43
votes
4answers
40k views

How to avoid being asked passphrase each time I push to Bitbucket

I set up my ssh stuff with the help of this guide, and it used to work well (I could run hg push without being asked for a passphrase). What could have happened between then and now, considering that ...
42
votes
8answers
28k views

SSH to decrypt encrypted LVM during headless server boot?

When I installed Ubuntu 10.04 and, now, 10.10, I was offered the option of enabling "encrypted LVM" for my hard drive. After choosing that option, I am prompted for my password during boot to decrypt ...
41
votes
5answers
24k views

How can I tell what version of OS X I'm on from the command line?

I frequently find myself SSHing into various OS X machines, and it'd be useful if I could tell what version of OS X I was on when I'm doing that. uname -a doesn't quite work, since Darwin kernel ...
40
votes
6answers
43k views

rsync all files of remote machine over SSH without root user?

I have this command to backup a remote machine. The problem is that I need root rights to read and copy all files. I have no root user enabled for security reasons and use sudo the Ubuntu way. Would I ...
40
votes
2answers
7k views

Is it safe to give out my SSH public key for work?

I currently work remotely for a number of organizations which need me to access their servers regularly for maintenance and upgrades. Is it safe for me to add my RSA public SSH key to the .ssh/...
40
votes
4answers
18k views

What is a better way to deal with server disconnects of sshfs mounts?

I have several directories mounted through sshfs. I sometimes get disconnects from the server (not configurable by me). I usually mount the directories like this sshfs user@server.example.com:/home/...
39
votes
4answers
50k views

Specify identity file (id_rsa) with rsync

I need to make periodic backups of a directory on a remote server which is a virtual machine hosted by a research organisation. They mandate that access to VMs is through ssh keys, which is all good, ...
39
votes
6answers
43k views

How to speed my too-slow ssh login?

Running ssh user@hostname takes ~30s. Here's the scenario: this is a VM on the local LAN Windows and Mac machines get instant login am using Debian and I could reproduce with an Ubuntu machine ...
38
votes
5answers
15k views

How can I detect if the shell is controlled from SSH?

I want to detect from a shell script (more specifically .zshrc) if it is controlled through SSH. I tried the HOST variable but it's always the name of the computer which is running the shell. Can I ...
37
votes
4answers
63k views

Is there a command to list all open displays on a machine?

When SSH'd locally into my computer (don't ask, it's a workaround), I can't start graphical applications without running: export DISPLAY=:0.0 If I run this first and then run a graphical ...
37
votes
9answers
169k views

ssh_exchange_identification: read: Connection reset by peer

I am on OS X trying to ssh into a ubuntu 12.04 server. I was able to SSH in -- until abruptly stuff stopped working. I've read online to use the -v to debug this. Output is shown below. If I ssh into ...
36
votes
3answers
132k views

SSH login with clear text password as a parameter? [duplicate]

I need to login to a user that I've created on a remote host running Ubuntu. I can't use an ssh key because the ssh login will happen from a bash script ran within a server that I won't have access to ...
36
votes
5answers
133k 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, ...
36
votes
1answer
7k views

redirect sound (microphone) via ssh, how to telephone via ssh?

How can I redirect the microphone of one computer to listen to it on another computer via ssh? Which is the right device or which is the right command line? Some years ago it was easy and fun to ...
35
votes
7answers
20k 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 ...
35
votes
4answers
14k views

Can mouse wheel scrolling work in a Screen session?

Is there any way to use the mouse wheel to scroll through the output of a screen session? I can use the keypad scroll through previous output in screen after pressing ctrl+a [. Is it possible to do ...
34
votes
4answers
9k views

How do I remotely edit files via ssh?

I have to edit some files placed on some server I could reach via ssh. I would prefer to edit these files in customized vim on my workstation (I have not rights to change vim settings on remote server)...
34
votes
3answers
60k views

Can I connect to Windows machine from Linux shell?

I can connect to Linux machines from Windows using PuTTY/SSH. I want to do the other way round - connect to a Windows machine from Linux. Is this possible?