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NAME | SYNOPSIS | DESCRIPTION | ENVIRONMENT | FILES | EXIT STATUS | SEE ALSO | AUTHORS | COLOPHON |
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SSH-ADD(1) General Commands Manual SSH-ADD(1)
ssh-add — adds private key identities to the OpenSSH
authentication agent
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 ...
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.
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.
~/.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 is 0 on success, 1 if the specified command fails, and
2 if ssh-add is unable to contact the authentication agent.
ssh(1), ssh-agent(1), ssh-askpass(1), ssh-keygen(1), sshd(8)
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.
This page is part of the openssh (Portable OpenSSH) project.
Information about the project can be found at
http://www.openssh.com/portable.html. If you have a bug report
for this manual page, see ⟨http://www.openssh.com/report.html⟩.
This page was obtained from the tarball openssh-9.9p2.tar.gz
fetched from
⟨http://ftp.eu.openbsd.org/pub/OpenBSD/OpenSSH/portable/⟩ on
2025-08-11. 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
[email protected]
GNU June 17, 2024 SSH-ADD(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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