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ssh-agent [-c | -s] [-d] [command [args ...]]
ssh-agent [-c | -s] -k
DESCRIPTION
ssh-agent is a program to hold private keys used for public
key authentiM--
cation (RSA, DSA). The idea is that ssh-agent is started in
the beginM--
ning of an X-session or a login session, and all other win-
dows or proM--
grams are started as clients to the ssh-agent program.
Through use of
environment variables the agent can be located and automati-
cally used for
authentication when logging in to other machines using
ssh(1).
The options are as follows:
-c Generate C-shell commands on stdout. This is the
default if
SHELL looks like it's a csh style of shell.
-s Generate Bourne shell commands on stdout. This is
the default if
SHELL does not look like it's a csh style of shell.
-k Kill the current agent (given by the SSH_AGENT_PID
environment
variable).
-d Debug mode. When this option is specified ssh-agent
will not
fork.
If a commandline is given, this is executed as a subprocess
of the agent.
When the command dies, so does the agent.
The agent initially does not have any private keys. Keys
are added using
ssh-add(1). When executed without arguments, ssh-add(1)
adds the
$HOME/.ssh/identity file. If the identity has a passphrase,
ssh-add(1)
asks for the passphrase (using a small X11 application if
running under
X11, or from the terminal if running without X). It then
sends the idenM--
tity to the agent. Several identities can be stored in the
agent; the
agent can automatically use any of these identities. ssh-
There are two main ways to get an agent setup: Either the
agent starts a
new subcommand into which some environment variables are ex-
ported, or the
agent prints the needed shell commands (either sh(1) or
csh(1) syntax can
be generated) which can be evalled in the calling shell.
Later ssh(1)
looks at these variables and uses them to establish a con-
nection to the
agent.
A unix-domain socket is created (/tmp/ssh-
XXXXXXXX/agent.<pid>), and the
name of this socket is stored in the SSH_AUTH_SOCK environ-
ment variable.
The socket is made accessible only to the current user.
This method is
easily abused by root or another instance of the same user.
The SSH_AGENT_PID environment variable holds the agent's
PID.
The agent exits automatically when the command given on the
command line
terminates.
FILES
$HOME/.ssh/identity
Contains the protocol version 1 RSA authentication
identity of
the user. This file should not be readable by any-
one but the
user. It is possible to specify a passphrase when
generating the
key; that passphrase will be used to encrypt the
private part of
this file. This file is not used by ssh-agent but
is normally
added to the agent using ssh-add(1) at login time.
$HOME/.ssh/id_dsa
Contains the protocol version 2 DSA authentication
identity of
the user.
$HOME/.ssh/id_rsa
Contains the protocol version 2 RSA authentication
identity of
the user.
de Raadt and Dug Song removed many bugs, re-added newer fea-
tures and creM--
ated OpenSSH. Markus Friedl contributed the support for SSH
protocol
versions 1.5 and 2.0.
SEE ALSO
ssh(1), ssh-add(1), ssh-keygen(1), sshd(8)
BSD September 25, 1999
BSD
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