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_CONNECTION Identifies the client and server ends of the con‐
nection. The variable contains four space‐sepa‐
rated values: client IP address, client port num‐
ber, server IP address, and server port number.
SSH_ORIGINAL_COMMAND This variable contains the original command line
if a forced command is executed. It can be used
to extract the original arguments.
SSH_TTY This is set to the name of the tty (path to the
device) associated with the current shell or com‐
mand. If the current session has no tty, this
variable is not set.
SSH_TUNNEL Optionally set by sshd(8) to contain the interface
names assigned if tunnel forwarding was requested
by the client.
SSH_USER_AUTH Optionally set by sshd(8), this variable may con‐
tain a pathname to a file that lists the authenti‐
cation methods successfully used when the session
was established, including any public keys that
were used.
TZ This variable is set to indicate the present time
zone if it was set when the daemon was started
(i.e. the daemon passes the value on to new con‐
nections).
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 users are al‐
lowed to change their environment. For more information, see the
PermitUserEnvironment option in sshd_config(5).
FILES
~/.rhosts
This file is used for host‐based authentication (see above). On
some machines this file may need to be world‐readable if the
user’s home directory is on an NFS partition, because sshd(8)
reads it as root. Additionally, this file must be owned by the
user, and must not have write permissions for anyone else. The
recommended permission for most machines is read/write for the
user, and not accessible by others.
~/.shosts
This file is used in exactly the same way as .rhosts, but allows
host‐based authentication without permitting login with
rlogin/rsh.
~/.ssh/
This directory is the default location for all user‐specific
configuration and authentication information. There is no gen‐
eral requirement to keep the entire contents of this directory
secret, but the recommended permissions are read/write/execute
for the user, and not accessible by others.
~/.ssh/authorized_keys
Lists the public keys (DSA, ECDSA, Ed25519, RSA) that can be
used for logging in as this user. The format of this file is
described in the sshd(8) manual page. This file is not highly
sensitive, but the recommended permissions are read/write for
the user, and not accessible