ssh-add man page

ssh-add — adds private key identities to the authentication agent

Synopsis

ssh-add [-cDdkLlXx] [-E fingerprint_hash] [-t life] [file ...]

ssh-add -s pkcs11

ssh-add -e pkcs11

Description

ssh-add adds private key identities to the authentication agent, ssh-agent(1). When run without arguments, it adds the files ~/.ssh/id_rsa, ~/.ssh/id_dsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ed25519 and ~/.ssh/identity. After loading a private key, ssh-add will try to load corresponding certificate information from the filename obtained by appending -cert.pub to the name of the private key file. Alternative file names can be given on the command line.

If any file requires a passphrase, ssh-add asks for the passphrase from the user. The passphrase is read from the user's tty. ssh-add retries the last passphrase if multiple identity files are given.

The authentication agent must be running and the SSH_AUTH_SOCK environment variable must contain the name of its socket for ssh-add to work.

The options are as follows:

-c
Indicates that added identities should be subject to confirmation before being used for authentication. Confirmation is performed by ssh-askpass(1). Successful confirmation is signaled by a zero exit status from ssh-askpass(1), rather than text entered into the requester.
-D
Deletes all identities from the agent.
-d
Instead of adding identities, removes identities from the agent. If ssh-add has been run without arguments, the keys for the default identities and their corresponding certificates will be removed. Otherwise, the argument list will be interpreted as a list of paths to public key files to specify keys and certificates to be removed from the agent. If no public key is found at a given path, ssh-add will append .pub and retry.
-E fingerprint_hash
Specifies the hash algorithm used when displaying key fingerprints. Valid options are: “md5” and “sha256”. The default is “sha256”.
-e pkcs11
Remove keys provided by the PKCS#11 shared library pkcs11.
-k
When loading keys into or deleting keys from the agent, process plain private keys only and skip certificates.
-L
Lists public key parameters of all identities currently represented by the agent.
-l
Lists fingerprints of all identities currently represented by the agent.
-s pkcs11
Add keys provided by the PKCS#11 shared library pkcs11.
-t life
Set a maximum lifetime when adding identities to an agent. The lifetime may be specified in seconds or in a time format specified in sshd_config(5).
-X
Unlock the agent.
-x
Lock the agent with a password.

Environment

DISPLAY and SSH_ASKPASS
If ssh-add needs a passphrase, it will read the passphrase from the current terminal if it was run from a terminal. If ssh-add does not have a terminal associated with it but DISPLAY and SSH_ASKPASS are set, it will execute the program specified by SSH_ASKPASS (by default “ssh-askpass”) and open an X11 window to read the passphrase. This is particularly useful when calling ssh-add from a .xsession or related script. (Note that on some machines it may be necessary to redirect the input from /dev/null to make this work.)
SSH_AUTH_SOCK
Identifies the path of a UNIX-domain socket used to communicate with the agent.
SSH_USE_STRONG_RNG
The reseeding of the OpenSSL random generator is usually done from /dev/urandom. If the SSH_USE_STRONG_RNG environment variable is set to value other than 0 the OpenSSL random generator is reseeded from /dev/random. The number of bytes read is defined by the SSH_USE_STRONG_RNG value. Minimum is 14 bytes. This setting is not recommended on the computers without the hardware random generator because insufficient entropy causes the connection to be blocked until enough entropy is available.

Files

~/.ssh/identity
Contains the protocol version 1 RSA authentication identity of the user.
~/.ssh/id_dsa
Contains the protocol version 2 DSA authentication identity of the user.
~/.ssh/id_ecdsa
Contains the protocol version 2 ECDSA authentication identity of the user.
~/.ssh/id_ed25519
Contains the protocol version 2 Ed25519 authentication identity of the user.
~/.ssh/id_rsa
Contains the protocol version 2 RSA authentication identity of the user.

Identity files should not be readable by anyone but the user. Note that ssh-add ignores identity files if they are accessible by others.

Exit Status

Exit status is 0 on success, 1 if the specified command fails, and 2 if ssh-add is unable to contact the authentication agent.

See Also

ssh(1), ssh-agent(1), ssh-askpass(1), ssh-keygen(1), sshd(8)

Authors

OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0.

Referenced By

agent-transfer(1), amaddclient(8), autossh(1), gsissh(1), gsissh_config(5), gsisshd(8), gsissh-keygen(1), keychain(1), ksshaskpass(1), monkeysphere(1), scp(1), sftp(1), ssh(1), ssh-agent(1), ssh_config(5), ssh-copy-id(1), sshd(8), ssh-keygen(1), ssh-pkcs11-helper(8), x11-ssh-askpass.1x(1).

March 30 2015