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

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What is SSH - the protocol and what is ssh - the utility?

What is SSH - the protocol? What is ssh - the unix utility and how does it work? How is SSH protocol related to SFTP? What is sshd? Does the command su use ssh or sshd?
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What are the pros/cons of the various methods to block brute force SSH attacks?

There are a number of different packages out there to shut out IPs from which brute-force SSH attacks are launched on your system. For example: DenyHosts Sshguard fail2ban What are the pros/cons ...
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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 ...
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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 ...
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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 ...
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How do I copy all files and directories except certain ones over ssh?

Using the Linux command line, I use the scp command to copy up all the files and folders from a certain directory. However, I don't like to consume wasted bandwidth for copying up things I rarely ...
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what's the purpose of ssh-agent?

I've read the official definition: ssh-agent is a program to hold private keys used for public key authentication (RSA, DSA, ECDSA). The idea is that ssh-agent is started in the beginning of an ...
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Execute remote commands, completely detaching from the ssh connection

I have 2 computers, localpc and remoteserver. I need localpc to execute some commands on remoteserver. One of the things it needs to do is start a backup script that runs for a number of hours. I ...
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(SSH) Is it dangerous to close terminal without “exit”?

This happened many times. While the SSH active, I'm so tired and just close the terminal without exit Is it dangerous to doing like that?
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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 ...
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Answer yes in a bash script

I'm trying to do a git clone trough a bash script, but the first time that I run the script and the server is not known yet the script fails. I have something like this: yes | git clone ...
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How can I solve this ssh-agent problem?

I'm using Linux Mint, and have not been able to get gnome-keyring to unlock automatically at login, it seems. A symptom of my problem is as follows: $ ssh-add Identity added: /home/me/.ssh/id_rsa ...
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Which users are allowed to log in via SSH by default?

When I set up my Debian 6, I was wondering, which users apart from root whose password I know can log into my system via SSH? When I install Apache 2 a user called www-data gets created. Does this ...
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Is there ever a reason to use scp instead of rsync?

Is there a reason to use scp instead of rsync? I can see no reason for using scp ever again, rsync does everything that scp does, with more safety (can preserve symlinks etc).
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Understanding SSH tunnels

I have linux (Ubuntu) server which I have root access to through ssh (port 22) only. On that server there is a MySQL database listening on port 3306. Is it possible to use putty (on my machine) and ...
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Why SSH takes a long time to Connect

I have noticed that some Linux Servers in Network takes long time to connect using ssh. Situations:: There are two situations I have faced. 1: On some servers some times it takes a long time to ask ...
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Limits of SSH multiplexing

I have the following entry in my .ssh/config file Host AAA User BBB HostName CCC ControlMaster auto ControlPath ~/.ssh/%r@%h:%p The above allows me to multiplex multiple ssh ...
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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 ...
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Can SSH passwords be sniffed out over Wi-Fi?

When you ssh, can the password you enter to connect, be intercepted if you're using untrusted public Wi-Fi (coffee shop, library, airport, etc).
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Groups differ from the local ones when logging in remotely

We store our users in LDAP, alongside some groups that have meaning across different systems (organizational roles including wheel). There are also groups local to workstations, e.g. audio or video ...
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How do I trigger autocomplete without a tab key?

I'm ssh-ing to my machine using my iPhone with an app called ServerAuditior. It doesn't have tab key. See screenshot. How do I trigger autocomplete without the tab key? I don't want to type a lot of ...
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How do you copy the public key to a ssh-server?

Here is what I have tried, and I got an error: $ cat /home/tim/.ssh/id_rsa.pub | ssh tim@just.some.other.server 'cat >> .ssh/authorized_keys' Password: cat: >>: No such file or directory ...
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SCP from one server to another without password prompt

What is the best way of doing SCP from one box to the other without prompting for password? There are two servers: Server A (10.152.2.10): /home/oracle/export/files.txt Server B (10.152.2.11): ...
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Encrypting file only with SSH -priv-key?

Suppose I want to encrypt a file so that only I can read it, by knowing my SSH private key password. I am sharing a repo where I want to encrypt or obfuscate sensitive information. By that, I mean ...
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How to temporarily switch from ssh to my local shell?

I'm using cygwin. and use it with ssh to login into a ubuntu server. sometimes, I want to switch back to my cygwin and then quickly switch to ubuntu shell. How to do this?
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Does a `scp` transfer close when I close the shell?

I have scp transfer (from one remote server to another), that is quite big. So maybe I want close the computer from which I executed this command, will this end the transfer? I have ssh access to ...
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How to download a file through an SSH server?

I have a server in USA (Linux box B), and my home PC (Linux box A), and I need download a file from website C, The issue is, it is very slow to download a file direct from A, so I need download the ...
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How to close (kill) ssh ControlMaster connections manually

With the following .ssh/config configuration: ControlMaster auto ControlPath /tmp/ssh_mux_%h_%p_%r ControlPersist 4h How to close the persisting connection before the 4 hours? I know you can make ...
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Is my SSH key paired with me as a human, or with my user account on one machine?

In the past few days, I have been trying to acquaint myself with SSH, and I hope that I've understood it. One question remains, however -- is my key associated with me (as the user) or my user ...
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How to copy a file that is still being written over ssh?

Here is the situation: I am uploading a large file from client A to a server using sftp. I also need to download this file from the server to client B over ssh. What I would like to do is start ...
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Is there an easy way to update information in known_hosts when you know that a hosts key has changed?

If a host's operating system has been re-installed and had its public key regenerated sshing to it will of course fail because the new key doesn't match the old one. Is there an easier way to tell ...
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How can I lock my own account from remote ssh login with password?

I don't want to disable remote login with password altogether, but I want to make it so that my account is only accessible with key pair authentication (there are other users who wants to use ...
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OS X: how to keep the computer from sleeping during a ssh session

When I ssh into a OS X computer on my network the session lasts until the OS X goes into sleep mode. Is there a way to prevent this from happening during my SSH session, apart from physically bumping ...
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How can I configure a reverse SSH connection to the connecting computer?

I'm going to be deploying a number of machines in the near future which will be behind routers. It won't be feasible to set up dynamic DNS on each router and port forwarding, so is there a way I can ...
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How to SSH into a specific directory?

I frequently login to a server, then cd into a specific directory. Is it possible to simplify these two commands into one? ssh bob@foo cd /home/guest I'd like to avoid changing anything on 'foo' ...
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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 ...
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How to delete a file on remote machine via SSH by using a Shell Script?

I am writing a Shell Script where I have to delete a file on a remote machine via a Shell Script. Flow manually: ssh username@domain.com .. then at domain: cd ./some/where rm ...
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How do I work with GUI tools over a remote server?

I have an Ubuntu server running on EC2 (which I didn't install myself, just picked up an AMI). So far I'm using putty to work with it, but I am wondering how to work on it with GUI tools (I'm not ...
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Is an SSH connection faster if I lower the RSA key size?

I have a very slow connection, and I need to use SSH on it. How can I increase "the speed"? I mean is using big RSA keypairs a large overhead? Would lowering the key size increase the effective ...
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SSH automatic remote back ups

I have two machines, A and B. Machine A can ssh into B. A has a lot of free space. B's data is in a sort of risky situation. How do I back up all of B's data to A automatically. It does not have to ...
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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 ...
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Given keys in ~/.ssh/authorized_keys format, can you determine key strength easily?

~/.ssh/authorized_keys[2] contains the list of public keys. Unfortunately, each public key does not specify the key strength ( number of bits ). Is there a utility that can process this file line by ...
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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?
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Can I unfreeze bash or vim when SSH session freezes from timeout? [duplicate]

When my SSH session times out, the whole terminal freezes. Is there any way to break out of that connection? CTRL+C doesn't cut it.
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Copy input to clipboard over SSH?

Here's my usage case: I'm often connected to other computers over SSH for work and I often need to copy and paste documents/text from the server to locally running editors for writing examples and ...
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Advice for managing SSH keys

What is the best practice you have found for managing lots of SSH keypairs? I use SSH to connect to several systems, both at home and at work. I currently have a fairly small, manageable collection ...
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Can I pipe /dev/video over ssh

I have two computers, a desktop in my office ( with a webcam attached ) and a laptop somewhere else on the network. Usually I take a look at my office through my webcam by running ssh Office -Y ...
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How to open a port early in boot process to unlock LUKS via SSH

I have a fully encrypted server running Debian 7 and have set up dropbear and busybox to unlock the LUKS container via SSH (as described in this tutorial and in this U&L answer). Unfortunately, ...
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sudo over ssh: no tty present and no askpass program specified

I keep getting this error and have tried several ways discussed online to fix this and none are working for me. I have setup SSH keys so when I run 'ssh newton@host.com' it automatically logs me in, I ...
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GVim compiled from source opened via SSH -X does not copy paste on selection

I'm using SSH (with -X specified) from a Ubuntu box to a RHEL4 box and running GVim. It opens as expected in my local X, but the copy and paste via select doesn't work. I cannot select text in GVim ...