Environment variables

ssh typically sets or uses the following environment variables:

_ZOS_OPENSSH_DEBUG

Contains z/OS-specific debug information. This environment variable is only used internally and is not for external specification.

_ZOS_OPENSSH_DEBUG_TIMESTAMP

If this variable is specified to YES, it will contain the timestamp in the debug information. If it is specified to CPU, the CPU time will be used as the timestamp.

_ZOS_OPENSSH_MSGCAT

Identifies the OpenSSH message catalog to be used when sending OpenSSH error messages.

_ZOS_SMF_FD

Set to the file descriptor number used for interprocess communication during SMF-related processing. This environment variable is only used internally and is not for external specification.

_ZOS_USER_SSH_CONFIG

Specifies the path name of the z/OS-specific per-user OpenSSH client configuration file. The system-wide default is /etc/ssh/zos_ssh_config and the user's default is ~/.ssh/zos_user_ssh_config. If this variable is specified, it replaces the user's default file but not the system-wide default file. See zos_ssh_config and zos_user_ssh_config for the available keywords. The recommended permissions of the specified file are read/write for the user and not writable by others.

DISPLAY

Indicates the location of the X11 server. It is automatically set by ssh to point to a value of the form hostname:n where hostname indicates the host where the shell runs, and n is an integer greater than or equal to 1. ssh uses this special value to forward X11 connections over the secure channel. The user should normally not set DISPLAY explicitly, as that will render the X11 connection insecure (and require the user to manually copy any required authorization cookies).

HOME

Set to the path for the user's home directory.

LOGNAME

Synonym for USER.

MAIL

Set to the path of the user's mailbox.

PATH

Set to the default PATH, as compiled into ssh.

SSH_ASKPASS

If ssh needs a passphrase, it reads the passphrase from the current terminal if it was run from a terminal. If ssh does not have a terminal associated with it, but DISPLAY and SSH_ASKPASS are set, it executes the program specified by SSH_ASKPASS and opens an X11 window to read the passphrase. This is particularly useful when calling ssh from an .Xsession or related script. It is necessary to redirect the input from /dev/null to make this work.

SSH_AUTH_SOCK

Identifies the path of a UNIX-domain socket used to communicate with the agent.

SSH_CONNECTION

Identifies the client and server ends of the connection. The variable contains four space-separated values: client ip-address, client port number, server ip-address and server port number.

SSH_ORIGINAL_COMMAND

Contains the original command line if a forced command is executed. It can be used to extract the original arguments.

SSH_TTY

Set to the name of the tty (path to the device) associated with the current shell or command. If the current session has no tty, this variable is not set.

TZ

Set to indicate the present time zone if it was set when the daemon was started (the daemon passes the value on to new connections).

USER

Set to the name of the user logging in.

Additionally, ssh reads ~/.ssh/environment and adds lines of the format VARNAME=value to the environment if the file exists and if users are allowed to change their environment. For more information, see PermitUserEnvironment.