# ssh-add

## 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.
    


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