The Setting up public key authentication Generate an SSH Key Copy the key to a server Test the new key Troubleshooting How ssh-copy-id works Some best practices for SSH keys Use a passphrase when possible Add a command restriction when possible Managing SSH keys Command-line options Ssh-copy-id on Mac Installation using Homebrew Installation from MacPorts Installation using Curl Key based authentication in SSH is called public key authentication. The purpose of With OpenSSH, an SSH key is created using ssh-keygen. In the simplest form, just run Creating a key pair (public key and private key) only takes a minute. The key files are usually stored in the Once an SSH key has been created, the Use a command like the following to copy SSH key: This logs into the server host, and copies keys to the server, and configures them to grant access by adding them to the authorized_keys file. The copying may ask for a password or other authentication for the server. Only the public key is copied to the server. The private key should never be copied to another machine. Once the key has been copied, it is best to test it: The login should now complete without asking for a password. Note, however, that the command might ask for the passphrase you specified for the key. There are a number of reasons why the test might fail: The server might not be configured to accept public key authentication. Make sure /etc/ssh/sshd_config on the server contains If trying to login as root, the server might not be configured to allow root logins. Make sure Make sure the client allows public key authentication. Check that /etc/ssh/config includes Try adding OpenSSH only allows a maximum of five keys to be tried authomatically. If you have more keys, you must specify which key to use using the It also checks if the key already exists on the server. Unless the It further ensures that the key files have appropriate permissions. Generally, the user's home directory or any file or directory containing keys files should not be writable by anyone else. Otherwise someone else could add new authorized keys for the user and gain access. Private key files should not be readable by anyone else. SSH keys are very useful, but can lead to problems if they are not properly managed. They are access credentials just like user names and passwords. If they are not properly removed when people leave or systems are decommissioned, no-one may any longer know who really has access to which systems and data. Many large organizations have ended up having millions of SSH keys. It is recommended that keys used for single sign-on have a passphrase to prevent use of the key if it is stolen or inadvertantlyleaked. The ssh-agent and ssh-add programs can be used to avoid having to enter the passphrase every time the key is used. Generally all keys used for interactive access should have a passphrase. Keys without a passphrase are useful for fully automated processes. They allow shell scripts, programs, and management tools to log into servers unattended. This is often used for backups and data transfers between information systems. The Anyone having more than a few dozen servers is strongly recommended to manage SSH keys. Not managing the keys exposes the organization to substantial risks, including loss of confidentiality, insertion of fraudulent transactions, and outright destruction of systems. The The Universal SSH Key Manager is a widely used product for managing SSH keys. The sample below presents ssh-copy-id command line syntax: The options have the following meaning: -f Don't check if the key is already configured as an authorized key on the server. Just add it. This can result in multiple copies of the key in -i Specifies the identity file that is to be copied (default is -n Just print the key(s) that would be installed, without actually installing them. -o ssh_option Pass -p port Connect to the specifed SSH port on the server, instead of the default port 22. -h or -? Print usage summary. While MacOS includes SSH, it does not include You can test whether your Mac has it by opening a terminal window (Finder / Go / Utilities / Terminal) and typing If your system does not have it, there are many ways to install ssh-copy-id Mac version. To install it using Homebrew, use the following command. You need to have the The following command will install it using MacPorts. You need to have the The following command can be used to install a Mac version directly. Note that as a general rule we do not recommend piping any commands from the network to the shell, like this does. Only use this method if you fully trust the source. The advantage of this method is that it does not need any special software - ssh-copy-id
installs an SSH key on a server as an authorized key. Its purpose is to provide access without requiring a password for each login. This facilitates automated, passwordless logins and single sign-on using the SSH protocol.ssh-copy-id
tool is part of OpenSSH.Contents
Setting up public key authentication
ssh-copy-id
is to make setting up public key authentication easier. The process is as follows.Generate an SSH Key
ssh-keygen
and answer the questions. The following example illustates this.# ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/home/ylo/.ssh/id_rsa): mykey Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in mykey. Your public key has been saved in mykey.pub. The key fingerprint is: SHA256:GKW7yzA1J1qkr1Cr9MhUwAbHbF2NrIPEgZXeOUOz3Us ylo@klar The key's randomart image is: +---[RSA 2048]----+ |.*++ o.o. | |.+B + oo. | | +++ *+. | | .o.Oo.+E | | ++B.S. | | o * =. | | + = o | | + = = . | | + o o | +----[SHA256]-----+ #
~/.ssh
directory.Copy the key to a server
ssh-copy-id
command can be used to install it as an authorized key on the server. Once the key has been authorized for SSH, it grants access to the server without a password.ssh-copy-id -i ~/.ssh/mykey user@host
Test the new key
ssh -i ~/.ssh/mykey user@host
Troubleshooting
PubkeyAuthentication yes
. Remember to restart the sshd process on the server./etc/sshd_config
includes PermitRootLogin yes
, PermitRootLogin prohibit-password
, or without-password
. If it is set to forced-commands-only
, the key must be manually configured to use a forced command (see command=
option in ~/.ssh/authorized_keys
.PubkeyAuthentication yes
.-v
option to the ssh
command used for the test. Read the output to see what it says about whether the key is tried and what authentication methods the server is willing to accept.-i
option to ssh
.How ssh-copy-id works
ssh-copy-id
uses the SSH protocol to connect to the target host and upload the SSH user key. The command edits the authorized_keys
file on the server. It creates the .ssh
directory if it doesn't exist. It creates the authorized keys file if it doesn't exist. Effectively, ssh key copied to server.-f
option is given, each key is only added to the authorized keys file once.Some best practices for SSH keys
Use a passphrase when possible
Add a command restriction when possible
copy-id
tool does not automatically add command restrictions to keys. Using command restrictions is highly recommended when the key is used for automating operations, such as running a report for fetching some files. A command restriction is basically a command="<permitted command>"
option added to the beginning of the line in the server's authorized_keys file.Managing SSH keys
copy-id
tool can be dangerous. It can easily accidentally install multiple keys or unintended keys as authorized. The logic for choosing which key to install is convoluted. Extra authorized keys grant permanent access. They can later be used to spread attacks host-to-host, and the more keys there are, the higher the risk. It also violates all regulatory compliance requirements.Command-line options
ssh-copy-id [-f] [-n] [-i identity file] [-p port] [-o ssh_option] [user@]hostname
authorized_keys
files.~/.ssh/id_rsa
). If this option is not provided, this adds all keys listed by ssh-add -L
. Note: it can be multiple keys and adding extra authorized keys can easily happen accidentally! If ssh-add -L
returns no keys, then the most recently modified key matching ~/.ssh/id*.pub
, excluding those matching ~/.ssh/*-cert.pub
, will be used.-o ssh_option
to the SSH client when making the connection. This can be used for overriding configuration settings for the client. See ssh command line options and the possible configuration options in ssh_config.Ssh-copy-id on Mac
ssh-copy-id
out of the port. However, according to some sources MacOS 10.12.4 includes it, and presumably newever versions include it as well.ssh-copy-id
.Installation using Homebrew
brew
command installed.brew install ssh-copy-id
Installation from MacPorts
port
command installed.sudo port install openssh +ssh-copy-id
Installation using Curl
curl
comes preinstalled.curl -L https://raw.githubusercontent.com/beautifulcode/ssh-copy-id-for-OSX/master/install.sh | sh
FAQs
What is ssh-copy-id? How ssh-copy-id works? ›
ssh-copy-id is a useful tool for SSH connections to a remote host without using a password. Basically, it copies the SSH key into the remote host's authorized_keys file, which is by default in the $HOME/. ssh directory.
What is SSH id? ›An identity key is a private key that is used in SSH for granting access to servers. They are a kind of SSH key, used for public key authentication. In OpenSSH, new identity keys can be created using the ssh-keygen tool. The tool generates both a private key and a public key.
Does SSH-copy-ID work for Windows? ›The Windows version of OpenSSH client doesn't include a ssh-copy-id command. I don't know why. If it does one day, then this can be ignored. NOTE If you have Windows Subsystem for Linux (WSL) installed, you can use the linux version of ssh-copy-id instead.
How to generate SSH ID? ›- Run the ssh-keygen command. You can use the -t option to specify the type of key to create. ...
- The command prompts you to enter the path to the file in which you want to save the key. ...
- The command prompts you to enter a passphrase. ...
- When prompted, enter the passphrase again to confirm it.
The commands which you would need to use are mv (short from move) and cp (short from copy). By executing the above command you will move (rename) the file original_file to new_name. This will move all files (and folders) from the includes/ directory to the current working directory.
What is SSH-copy-id? ›Overview. ssh-copy-id is a useful tool for SSH connections to a remote host without using a password. Basically, it copies the SSH key into the remote host's authorized_keys file, which is by default in the $HOME/. ssh directory.
How does SSH work? ›Remote encrypted connections: SSH sets up a connection between a user's device and a faraway machine, often a server. It uses encryption to scramble the data that traverses the connection. An intercepting party would only find something like static — random data that means nothing unless it is decrypted.
Can two computers have the same SSH key? ›SSH Keys on Multiple Machines
You can only upload and use one SSH key at a time at the SDCC. If you own multiple machines (e.g., a desktop and a laptop), then you can generate a public/private key pair on one machine, upload the public key to the LDAP server, and copy the private key to your other machines.
- Use the ssh-copy-id command to append the public key in the local ~/.ssh/id_rsa.pub file to the ~/.ssh/authorized_keys file on the remote system, for example: ssh-copy-id remote_user@host.
- When prompted, enter the password for the remote system.
- Press the Windows key or open up the Start Menu. Type “cmd”.
- Under “Best Match”, click “Command Prompt”.
- In the command prompt, use the ssh-keygen command: ...
- The system will now generate the key pair and display the key fingerprint and a randomart image. ...
- Open your file explorer.
How does a SSH key look like? ›
SSH keys come in pairs, a public key that gets shared with services like GitHub, and a private key that is stored only on your computer. If the keys match, you're granted access. The cryptography behind SSH keys ensures that no one can reverse engineer your private key from the public one.
How do I get an SSH connection? ›- Go to System Settings.
- Click General in the left menu.
- Locate and open Sharing.
- Enable Remote Login to allow SSH access to the device.
- Open a Command prompt window on your technician PC.
- Connect to the device: To connect using a username and password: ssh [email protected]. ...
- Enter the password for your user if you're connecting with a username and password, or if you configured your key to require a password.
- Open the terminal on your computer.
- Type ssh, followed by a space. ...
- If you see a message stating “Are you sure you want to continue connecting” type yes, then click the Enter key.
- You will then be prompted to enter your password.
The public key can be shared freely with any SSH server to which the user wishes to connect. These keys are normally managed by an organization's IT team, or better yet, with the help of a trusted Certificate Authority (CA) to ensure they are stored safely.
How do I get my SSH? ›- Press the Windows key or open up the Start Menu. Type “cmd”.
- Under “Best Match”, click “Command Prompt”.
- In the command prompt, use the ssh-keygen command: ...
- The system will now generate the key pair and display the key fingerprint and a randomart image. ...
- Open your file explorer.
SSH or Secure Shell is a network communication protocol that enables two computers to communicate (c.f http or hypertext transfer protocol, which is the protocol used to transfer hypertext such as web pages) and share data.
How do I find my SSH username and password? ›1 Answer. The Login is the "username@ipaddress" of the remote computer.It prompts for password automatically when you connect. This username and password are system wide basically. For more specific details about enabling ssh in cPanel and connecting refer here.
How do I access SSH? ›- Open a Terminal session.
- Run the following command: ssh -p port user@IP where port represents the port number, user represents your username, and IP represents your IP address. For example: user@workstation:~$ ssh -p 22 [email protected].
- Enter your password.