NAME

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

SYNOPSIS

DESCRIPTION

ssh-add adds private key identities to the authentication agent, ssh-agent(1).

For RSA, ECDSA, Ed25519, or MLDSA identity may contain X.509 certificate that match private key. This certificate will be loaded as well. Also identity may contain extra X.509 certificates. Agent client uses those extra certificates along with certificates from system default X.509 store to build chain of certificates leading to a trusted certificate authority.

When run without arguments, it adds the files ~/.ssh/id_rsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ed25519, and ~/.ssh/id_mldsa. After loading a private key, ssh-add will try to load corresponding custom 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 (X.509 or custom) 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. If the argument list consists of “-” then ssh-add will read public keys to be removed from standard input.

-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 listing X.509 certificate based identities prints public key instead certificate distinguished name.

When loading keys into or deleting keys from the agent, process plain private keys only and skip custom certificates. In this case it is ignored for X.509 certificate based identities.

-L

Lists public key parameters of all identities currently represented by the agent. X.509 certificates are displayed with their “Distinguished Name”.

-l

Lists fingerprints of all identities currently represented by the agent.

-Q

Query the agent for the list of protocol extensions it supports. Note: not all agents support this query.

-q

Be quiet after a successful operation.

-s pkcs11

Add keys provided by the PKCS#11 shared library pkcs11.

-T pubkey ...

Tests whether the private keys that correspond to the specified pubkey files are usable by performing sign and verify operations on each.

-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).

-v

Verbose mode. Causes ssh-add to print debugging messages about its progress. This is helpful in debugging problems. Multiple -v options increase the verbosity. The maximum is 3.

-X

Unlock the agent.

-x

Lock the agent with a password.

ENVIRONMENT

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 is set, it will execute the program specified by SSH_ASKPASS that may open a X11 window to read the passphrase. Note if SSH_ASKPASS is not set will be executed program ssh-askpass located in “libexec” directory. 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.)

Remark: On Android DISPLAY is ignored.

SSH_ASKPASS_REQUIRE

Allows further control over the use of an askpass program. If this variable is set to “never” then ssh-add will never attempt to use one. If it is set to “prefer”, then ssh-add will prefer to use the askpass program instead of the TTY when requesting passwords. Finally, if the variable is set to “force”, then the askpass program will be used for all passphrase input regardless of whether DISPLAY is set.

SSH_AUTH_SOCK

Identifies the path of a UNIX-domain socket used to communicate with the agent.

FILES

~/.ssh/id_ecdsa

 

~/.ssh/id_ed25519

 

~/.ssh/id_mldsa

 

~/.ssh/id_rsa

Contains the ECDSA, Ed25519, MLDSA, or RSA user authentication identity.

For RSA, ECDSA, Ed25519, or MLDSA identity file may contain X.509 certificate that match private key and extra X.509 certificates.

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

PKIX-SSH 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. Roumen Petrov contributed the support for X.509 certificate based public-key algorithms, rewrite use of cryptography library API, added newer features, and created PKIX-SSH.