NAME

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

SYNOPSIS

     ssh-add [-CcDdKkLlqvXx] [-E fingerprint_hash] [-H hostkey_file] [-h destination_constraint]
             [-S provider] [-t life] [file ...]
     ssh-add -s pkcs11 [-Cv] [certificate ...]
     ssh-add -e pkcs11
     ssh-add -T pubkey ...

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_ecdsa, ~/.ssh/id_ecdsa_sk,
     ~/.ssh/id_ed25519 and ~/.ssh/id_ed25519_sk.  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      When loading keys into or deleting keys from the agent, process certificates only
             and skip plain keys.

     -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.  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.

     -H hostkey_file
             Specifies a known hosts file to look up hostkeys when using destination-constrained
             keys via the -h flag.  This option may be specified multiple times to allow multiple
             files to be searched.  If no files are specified, ssh-add will use the default
             ssh_config(5) known hosts files: ~/.ssh/known_hosts, ~/.ssh/known_hosts2,
             /etc/ssh/ssh_known_hosts, and /etc/ssh/ssh_known_hosts2.

     -h destination_constraint
             When adding keys, constrain them to be usable only through specific hosts or to
             specific destinations.

             Destination constraints of the form ‘[user@]dest-hostname’ permit use of the key
             only from the origin host (the one running ssh-agent(1)) to the listed destination
             host, with optional user name.

             Constraints of the form ‘src-hostname>[user@]dst-hostname’ allow a key available on
             a forwarded ssh-agent(1) to be used through a particular host (as specified by
             ‘src-hostname’) to authenticate to a further host, specified by ‘dst-hostname’.

             Multiple destination constraints may be added when loading keys.  When attempting
             authentication with a key that has destination constraints, the whole connection
             path, including ssh-agent(1) forwarding, is tested against those constraints and
             each hop must be permitted for the attempt to succeed.  For example, if key is
             forwarded to a remote host, ‘host-b’, and is attempting authentication to another
             host, ‘host-c’, then the operation will be successful only if ‘host-b’ was permitted
             from the origin host and the subsequent ‘host-b>host-c’ hop is also permitted by
             destination constraints.

             Hosts are identified by their host keys, and are looked up from known hosts files by
             ssh-add.  Wildcards patterns may be used for hostnames and certificate host keys are
             supported.  By default, keys added by ssh-add are not destination constrained.

             Destination constraints were added in OpenSSH release 8.9.  Support in both the
             remote SSH client and server is required when using destination-constrained keys
             over a forwarded ssh-agent(1) channel.

             It is also important to note that destination constraints can only be enforced by
             ssh-agent(1) when a key is used, or when it is forwarded by a cooperating ssh(1).
             Specifically, it does not prevent an attacker with access to a remote SSH_AUTH_SOCK
             from forwarding it again and using it on a different host (but only to a permitted
             destination).

     -K      Load resident keys from a FIDO authenticator.

     -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.

     -q      Be quiet after a successful operation.

     -S provider
             Specifies a path to a library that will be used when adding FIDO authenticator-
             hosted keys, overriding the default of using the internal USB HID support.

     -s pkcs11
             Add keys provided by the PKCS#11 shared library pkcs11.  Certificate files may
             optionally be listed as command-line arguments.  If these are present, then they
             will be loaded into the agent using any corresponding private keys loaded from the
             PKCS#11 token.

     -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

     DISPLAY, SSH_ASKPASS and SSH_ASKPASS_REQUIRE
             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.

             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.

     SSH_SK_PROVIDER
             Specifies a path to a library that will be used when loading any FIDO authenticator-
             hosted keys, overriding the default of using the built-in USB HID support.

FILES

     ~/.ssh/id_ecdsa
     ~/.ssh/id_ecdsa_sk
     ~/.ssh/id_ed25519
     ~/.ssh/id_ed25519_sk
     ~/.ssh/id_rsa
             Contains the ECDSA, authenticator-hosted ECDSA, Ed25519, authenticator-hosted
             Ed25519 or 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.