ssh-add(1) — Linux manual page


SSH-ADD(1)             BSD General Commands Manual            SSH-ADD(1)

NAME         top

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

SYNOPSIS         top

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

DESCRIPTION         top

     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, ~/.ssh/id_ed25519_sk, and ~/.ssh/id_dsa.  After
     loading a private key, ssh-add will try to load corresponding
     certificate information from the filename obtained by appending 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

     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

     -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

     -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.

     -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

     -X      Unlock the agent.

     -x      Lock the agent with a password.

ENVIRONMENT         top

             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.

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

             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         top

             Contains the DSA, 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

EXIT STATUS         top

     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         top

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

AUTHORS         top

     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.

COLOPHON         top

     This page is part of the openssh (Portable OpenSSH) project.
     Information about the project can be found at  If you have a bug report for
     this manual page, see ⟨⟩.  This
     page was obtained from the tarball openssh-9.3p1.tar.gz fetched
     from ⟨⟩ on
     2023-06-23.  If you discover any rendering problems in this HTML
     version of the page, or you believe there is a better or more up-
     to-date source for the page, or you have corrections or
     improvements to the information in this COLOPHON (which is not part
     of the original manual page), send a mail to

BSD                         February 4, 2022                         BSD