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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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ssh-agent [options] [command [arguments] ]

Hold private keys used for public key authentication. ssh-agent is usually executed at the beginning of an X or login session; then all other windows or programs given as command are run as clients of ssh-agent. When a command is specified, the command and any arguments are executed. The agent dies when the command completes. Use ssh-add to add keys (identities) to the agent. Operations that require a private key are performed by the agent, which returns the results to the requestor. When using ssh-agent, you must specify a shell—for example:

$ ssh-agent /bin/bash

You can then use ssh-add to add identities.


-a bind_addr

Bind the agent to the socket bind_addr (default is /tmp/ssh-nnnnnnnn/agent, where nnnnnnnn is a generated number).


Write csh commands to standard output. This is the default if the environment variable SHELL looks like a csh-type shell.


Debug mode.


Kill the current agent.


Write Bourne shell commands to standard output. This is the default if the environment variable SHELL does not look like a csh-type command.

-t life

Set a default value for maximum identity lifetime for added identities. May be specified in seconds or in a format specified in sshd(8). This value can be overridden by a lifetime specified for an identity with ssh-add. The default maximum lifetime is forever.

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