1SSH-AGENT(1) General Commands Manual SSH-AGENT(1) 2 3NAME 4 ssh-agent M-bM-^@M-^S authentication agent 5 6SYNOPSIS 7 ssh-agent [-c | -s] [-d] [-a bind_address] [-E fingerprint_hash] 8 [-t life] [command [arg ...]] 9 ssh-agent [-c | -s] -k 10 11DESCRIPTION 12 ssh-agent is a program to hold private keys used for public key 13 authentication (RSA, DSA, ECDSA, Ed25519). ssh-agent is usually started 14 in the beginning of an X-session or a login session, and all other 15 windows or programs are started as clients to the ssh-agent program. 16 Through use of environment variables the agent can be located and 17 automatically used for authentication when logging in to other machines 18 using ssh(1). 19 20 The agent initially does not have any private keys. Keys are added using 21 ssh-add(1). Multiple identities may be stored in ssh-agent concurrently 22 and ssh(1) will automatically use them if present. ssh-add(1) is also 23 used to remove keys from ssh-agent and to query the keys that are held in 24 one. 25 26 The options are as follows: 27 28 -a bind_address 29 Bind the agent to the UNIX-domain socket bind_address. The 30 default is $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>. 31 32 -c Generate C-shell commands on stdout. This is the default if 33 SHELL looks like it's a csh style of shell. 34 35 -d Debug mode. When this option is specified ssh-agent will not 36 fork. 37 38 -E fingerprint_hash 39 Specifies the hash algorithm used when displaying key 40 fingerprints. Valid options are: M-bM-^@M-^\md5M-bM-^@M-^] and M-bM-^@M-^\sha256M-bM-^@M-^]. The 41 default is M-bM-^@M-^\sha256M-bM-^@M-^]. 42 43 -k Kill the current agent (given by the SSH_AGENT_PID environment 44 variable). 45 46 -s Generate Bourne shell commands on stdout. This is the default if 47 SHELL does not look like it's a csh style of shell. 48 49 -t life 50 Set a default value for the maximum lifetime of identities added 51 to the agent. The lifetime may be specified in seconds or in a 52 time format specified in sshd_config(5). A lifetime specified 53 for an identity with ssh-add(1) overrides this value. Without 54 this option the default maximum lifetime is forever. 55 56 If a commandline is given, this is executed as a subprocess of the agent. 57 When the command dies, so does the agent. 58 59 The idea is that the agent is run in the user's local PC, laptop, or 60 terminal. Authentication data need not be stored on any other machine, 61 and authentication passphrases never go over the network. However, the 62 connection to the agent is forwarded over SSH remote logins, and the user 63 can thus use the privileges given by the identities anywhere in the 64 network in a secure way. 65 66 There are two main ways to get an agent set up: The first is that the 67 agent starts a new subcommand into which some environment variables are 68 exported, eg ssh-agent xterm &. The second is that the agent prints the 69 needed shell commands (either sh(1) or csh(1) syntax can be generated) 70 which can be evaluated in the calling shell, eg eval `ssh-agent -s` for 71 Bourne-type shells such as sh(1) or ksh(1) and eval `ssh-agent -c` for 72 csh(1) and derivatives. 73 74 Later ssh(1) looks at these variables and uses them to establish a 75 connection to the agent. 76 77 The agent will never send a private key over its request channel. 78 Instead, operations that require a private key will be performed by the 79 agent, and the result will be returned to the requester. This way, 80 private keys are not exposed to clients using the agent. 81 82 A UNIX-domain socket is created and the name of this socket is stored in 83 the SSH_AUTH_SOCK environment variable. The socket is made accessible 84 only to the current user. This method is easily abused by root or 85 another instance of the same user. 86 87 The SSH_AGENT_PID environment variable holds the agent's process ID. 88 89 The agent exits automatically when the command given on the command line 90 terminates. 91 92FILES 93 $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid> 94 UNIX-domain sockets used to contain the connection to the 95 authentication agent. These sockets should only be readable by 96 the owner. The sockets should get automatically removed when the 97 agent exits. 98 99SEE ALSO 100 ssh(1), ssh-add(1), ssh-keygen(1), sshd(8) 101 102AUTHORS 103 OpenSSH is a derivative of the original and free ssh 1.2.12 release by 104 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo 105 de Raadt and Dug Song removed many bugs, re-added newer features and 106 created OpenSSH. Markus Friedl contributed the support for SSH protocol 107 versions 1.5 and 2.0. 108 109OpenBSD 5.7 December 21, 2014 OpenBSD 5.7 110