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SSH Tectia 
PreviousNextUp[Contents] [Index]

    About This Document >>
    Installing SSH Tectia Server for IBM z/OS >>
    Getting Started with SSH Tectia Server for IBM z/OS >>
    Configuring the Server >>
    Configuring the Client >>
    Authentication >>
    Transferring Files >>
    Tunneling >>
    Troubleshooting SSH Tectia Server for IBM z/OS >>
    Advanced Information >>
    Man Pages >>
        scp2
        sftp2
        ssh-add2
        ssh-agent2
        ssh-certd
        ssh_certd_config
        ssh-certview >>
        ssh-cmpclient >>
        ssh-dummy-shell
        ssh-ekview
        ssh-externalkeys
        ssh-keygen2
        ssh-probe2
        ssh-scepclient >>
        ssh-sft-stage
        ssh2
        ssh2_config
        sshd-check-conf
        sshd2
        sshd2_config
        sshd2_subconfig
        sshregex
    Log Messages >>

ssh2

SSH2(1)                        SSH2                       SSH2(1)


NAME
       ssh2 - Secure Shell client (remote login program) on z/OS


SYNOPSIS
       ssh2  [-l username]  [-n]  [+a]  [-a]  [-i file] [-K file]
       [-F file] [-t] [--verbose] [-v]  [-d debug_level]  [--ver-
       sion]  [-V]  [-q]  [-f[o]]  [-e char] [-c cipher] [-m MAC]
       [-p port]   [-S]   [-L [protocol/][listen-address:]listen-
       port:dst-host:dst-port] [-L socks/listen-port] [-R [proto-
       col/][listen-address:]listen-port:dst-host:dst-port]  [-g]
       [+g]  [+C]  [-C]  [-E provider]  [-I initstring] [-4] [-6]
       [-1 [ti]]    [-o options]     [-h]     [--help]     [user-
       name@]host[#port] [command]


DESCRIPTION
       ssh2  (Secure  Shell)  is  a  program  for logging in on a
       remote machine and executing commands on a remote machine.
       It is intended for replacing rlogin and rsh, and providing
       secure, encrypted communication channels between two hosts
       over  an unsecured network.  X11 connections and arbitrary
       TCP/IP ports can also be forwarded over such secure  chan-
       nels.

       ssh2  connects  to and logs in on the specified host.  The
       users must prove their identities to  the  remote  machine
       using some authentication method.

       Public-key  authentication  is based on the use of digital
       signatures.  Each user creates a public/private  key  pair
       for  authentication purposes.  The server knows the user's
       public key, and only the user has the  private  key.   The
       filenames  of private keys that are used in authentication
       are set in $HOME/.ssh2/identification. When the user tries
       to  authenticate, the server checks $HOME/.ssh2/authoriza-
       tion for filenames of matching public  keys  and  sends  a
       challenge  to  the user end.  The user is authenticated by
       signing the challenge with the private key.  See the FILES
       section  below  for more information on identification and
       authorization files.

       Private/public key pairs  can  be  created  with  ssh-key-
       gen2(1).  See  ssh-agent2(1) for information on how to use
       public-key authentication in conjunction with an authenti-
       cation agent.

       If other authentication methods fail, ssh2 will prompt for
       a password.  Since all  communication  is  encrypted,  the
       password will not be available for eavesdroppers.

       When  the user's identity has been accepted by the server,
       the server either executes the given command, or  logs  in
       on  the  machine  and  gives the user a normal shell.  All
       communication with the remote command  or  shell  will  be
       automatically encrypted.

       If no pseudo-tty has been allocated, the session is trans-
       parent and can be used to reliably transfer binary data.

       The session terminates when the command or  shell  on  the
       remote  machine  exits  and all X11 and TCP/IP connections
       have been closed.  The exit status of the  remote  program
       is returned as the exit status of ssh2.

       If the user is using X11 (the DISPLAY environment variable
       is set), the connection to the X11  display  is  automati-
       cally  forwarded to the remote side in such a way that any
       X11 programs started from the shell (or command)  will  go
       through  the  encrypted channel, and the connection to the
       real X server will be made from  the  local  machine.  The
       user  should not manually set DISPLAY. Forwarding X11 con-
       nections can be configured on the command line or in  con-
       figuration files.

       The  DISPLAY  value  set  by ssh2 will point to the server
       machine, but with a  display  number  greater  than  zero.
       This is normal, and happens because ssh2 creates a "proxy"
       X server on the server machine for forwarding the  connec-
       tions over the encrypted channel.

       ssh2 will also automatically set up the Xauthority data on
       the server machine. For this purpose, it will  generate  a
       random  authentication  cookie, store it in the Xauthority
       data on the server, and verify that any forwarded  connec-
       tions  carry  this  cookie  and  replace  it with the real
       cookie when the connection is opened.  The real  authenti-
       cation  cookie is never sent to the server machine (and no
       cookies are sent in the plain).

       If the user is using an authentication agent, the  connec-
       tion to the agent is automatically forwarded to the remote
       side unless disabled on the command line or in a  configu-
       ration file.

       Forwarding of arbitrary TCP/IP connections over the secure
       channel can be specified either on the command line or  in
       a  configuration  file.  TCP/IP forwarding can be used for
       secure connections  to  electronic  purses  or  for  going
       through firewalls.

       ssh2  automatically  maintains  and checks a database con-
       taining the public host keys.  When logging in on  a  host
       for the first time, the host's public key is stored in the
       file .ssh2/hostkey_PORTNUMBER_HOSTNAME.pub in  the  user's
       home  directory.  If a host's identification changes, ssh2
       issues a warning and disables the password  authentication
       in  order to prevent man-in-the-middle attacks which could
       otherwise be used to circumvent the  encryption  or  steal
       passwords.

       ssh2  has  built-in support for SOCKS versions 4 and 5 for
       traversing firewalls.  See the ENVIRONMENT  section.  Note
       that  the  SOCKS5 support does not include support for the
       SOCKS authentication methods.


OPTIONS
       -l username
              Logs in on the remote machine as user username.

       -n     Redirects input from /dev/null (i.e. does not  read
              stdin).   This  option can also be specified in the
              configuration file.

       +a     Enables authentication agent forwarding  (default).

       -a     Disables authentication agent forwarding.

       -i file
              Specifies  the identity file for public-key authen-
              tication.  This option can also be specified in the
              configuration file.

       -K file
              Specifies  the  key file for public-key authentica-
              tion.   Multiple  -K  options  are  allowed.   This
              option  can  also be specified in the configuration
              file.

       -F file
              Specifies  an additional configuration file to use.
              Note: $HOME/.ssh2/ssh2_config is  still  read,  but
              options  specified here will be overridden by file.

       -t     Tty allocation, that is, allocates a tty even if  a
              command  is  given.  This option can also be speci-
              fied in the configuration file.

       -v,--verbose
              Enables verbose mode.  Displays  verbose  debugging
              messages.   Equivalent  to  -d  2.  This option can
              also be specified in the configuration file.

       -d debug_level
              Prints  extensive  debug  information  to   stderr.
              debug_level is either a number, from 0 to 99, where
              99 specifies that all debug information  should  be
              displayed, or a comma-separated list of assignments
              of the format ModulePattern=debug_level, for  exam-
              ple "*=10,sshd2=2".  This should be the first argu-
              ment on the command line.

       -V,--version
              Displays version string.

       -q     Makes ssh2 quiet, so that it does not  display  any
              warning  messages.   This option can also be speci-
              fied in the configuration file.

       -f[o]  Forks  into  background after authentication.  This
              option can also be specified in  the  configuration
              file  (GoBackground).  Implies -S (unless a command
              is specified) and -n.  When forwardings  have  been
              specified, this option makes ssh2 stay in the back-
              ground, so that it waits  for  connections  indefi-
              nitely  (it  has  to  be killed to stop listening).
              With an optional o argument, it goes to  'one-shot'
              mode,  which  means  that  once  all  channels  are
              closed, ssh2 exits.

       -e char
              Sets  the escape character.  Use 'none' to disable.
              This option can also be specified in the configura-
              tion file (default: ~).

       -c cipher
              Selects  the  encryption  algorithm.   Multiple  -c
              options are allowed, but a single -c flag can  have
              only one cipher.  This option can also be specified
              in the configuration file  (see  ssh2_config(5) for 
              a list of known algorithms).

       -m MAC Selects the MAC (Message Authentication Code) algo-
              rithm.  Multiple -m options are allowed, but a sin-
              gle -m flag can have only one MAC.  This option can
              also be specified in the  configuration  file  (see
              ssh2_config(5) for a list of known algorithms).

       -p port
              Port to connect to on the remote host.  This option
              can also be specified in the configuration file.

       -S     Does not request a session channel.   This  can  be
              used  with  port-forwarding  requests  if a session
              channel (and tty) is not needed, or the server does
              not give one.

       -L [protocol/][listen-address:]listen-port:dst-host:dst-port or

       -L socks/[listen-address:]listen-port
              The  given  port on the local (client) host is for-
              warded to the given host and  port  on  the  remote
              side.   This  allocates a listener port listen-port
              on the local side.  Whenever a connection  is  made
              to  this listener, the connection is forwarded over
              the secure channel and a connection is made to dst-
              host:dst-port  from the remote machine (this latter
              connection will not be secure, it is a  normal  TCP
              connection).  Port forwarding can also be specified
              in the configuration file.

              Only root can forward privileged ports.  Giving the
              argument  protocol  enables  protocol-specific for-
              warding.   The  protocols   implemented   are   tcp
              (default,  no  special  processing), ftp (temporary
              forwarding is created for FTP data channels, effec-
              tively  securing the whole FTP session), and socks.

              With socks, the ssh2 client will  act  as  a  SOCKS
              server for other applications, creating forwards as
              requested by the SOCKS transaction.  This  supports
              both  SOCKS4 and SOCKS5. For example, ssh2 supports
              SOCKS5, so you can configure it to use  your  socks
              forward  by  setting  an  appropriate value for the
              SocksServer  configuration  option.  See  ssh2_con-
              fig(5).  Use  it with care, as other clients may be
              able to connect  to  the  forwarded  port  as  well
              (depending  on  your  listen-address  setting,  and
              whether the client machine has other users  besides
              you).  If  you  are  using  it to ease traversing a
              firewall, consult the administrator of the destina-
              tion network for the policy.

              If  listen-address is given, only that interface on
              the client is  listened.  If  it  is  omitted,  all
              interfaces are listened.  Parameters listen-address
              and dst-host can optionally be enclosed  in  square
              brackets  [] to allow semicolons in the parameters.

       -R [protocol/][listen-address:]listen-port:dst-host:dst-port
              Remote  port  forwarding.  The  given  port  on the
              remote (server) host is forwarded to the given host
              and  port on the local side.  This allocates a lis-
              tener port listen-port  on  the  remote  side,  and
              whenever  a  connection  is  made to this port, the
              connection is forwarded over the secure channel and
              further to dst-host:dst-port from the local machine
              (this latter connection will not be secure,  as  it
              is a normal TCP connection).

              Privileged ports can be forwarded only when logging
              in as root on the remote machine.  Giving the argu-
              ment protocol enables protocol-specific forwarding.
              The protocols implemented are tcp (default, no spe-
              cial  processing)  and ftp (temporary forwarding is
              created for FTP data channels, effectively securing
              the whole FTP session).

              If  listen-address is given, only that interface on
              the server is  listened.  If  it  is  omitted,  all
              interfaces are listened.  Parameters listen-address
              and dst-host can optionally be enclosed  in  square
              brackets  [] to allow semicolons in the parameters.

       -g     Gateways  ports, which means that also remote hosts
              may connect to locally forwarded  ports.  Note  the
              logic of + and - in this option.

       +g     Does  not  gateway ports. Listens to tunneling con-
              nections originating only from the localhost.  Note
              the logic of + and - in this option.

       +C     Enables compression.

       -C     Disables compression (default).

       -E provider
              Uses  external  key provider provider for accessing
              external keys for user authentication. This feature
              is  only  available  when  external  key support is
              included in the software.  See  ssh-externalkeys(5)
              for further information.

       -I initstring
              Uses  initialization string initstring for external
              key provider for accessing external keys  for  user
              authentication. This feature is only available when
              external key support is included in  the  software.
              See ssh-externalkeys(5) for further information.

       -4     Uses IPv4 to connect.

       -6     Uses IPv6 to connect.

       -1[ti] Fallback  to  SSH1  protocol.  Additional letter is
              mandatory: i means internal emulation, t means tra-
              ditional mechanism (call to ssh1 executable).

       -o options
              Can be used to give options in the format  used  in
              the configuration files.  This is useful for speci-
              fying options for which there is no  separate  com-
              mand-line  flag.  The option has the same format as
              a line in the configuration file (for  example,  -o
              "ConfigKeyword=value").    Comment  lines  are  not
              accepted.  Where applicable, egrep regex format  is
              used.

       -h,--help
              Displays a short help on command-line options.

CONFIGURATION FILES
       ssh2 obtains configuration data from the following sources
       (in this order): system's global configuration file (typi-
       cally  /etc/ssh2/ssh2_config),  user's  configuration file
       ($HOME/.ssh2/ssh2_config) and  the  command-line  options.
       For each parameter, the last obtained value will be effec-
       tive.

       Commercial  packages  use  a   license   file   (typically
       /etc/ssh2/license_ssh2.dat)  to  specify  the  type of the
       license.  For more  information,  see  SSH  Tectia  Server
       Administrator's Guide.

       For the format of ssh2_config, see ssh2_config(5).


ESCAPE SEQUENCES
       ssh2  supports  escape  sequences to manage a running ses-
       sion.  In order for an escape sequence to take effect,  it
       must  be  typed  directly after a newline character (read:
       press Enter first).  The escape  sequences  are  not  dis-
       played on screen during typing.

       ~.     Terminates the connection.

       ~^Z    Suspends  the  session  (press control-Z, not ^ and
              Z).

       ~~     Sends the escape character.

       ~#     Lists forwarded connections.

       ~-     Disables the escape character irrevocably.

       ~?     Displays a summary of escape sequences.

       ~r     Initiates rekeying manually.

       ~s     Gives connection statistics, including  server  and
              client  version,  packets in, packets out, compres-
              sion, key  exchange  algorithms,  public-key  algo-
              rithms, and symmetric ciphers.

       ~c     Gives statistics for individual channels (data win-
              dow sizes etc). This is for debugging purposes.

       ~V     Dumps the client version number to  stderr  (useful
              for troubleshooting).


ENVIRONMENT
       ssh2  will  normally  set  the following environment vari-
       ables:

       DISPLAY
              The DISPLAY variable indicates the location of  the
              X11  server.  It  is  automatically  set by ssh2 to
              point to a value of the form hostname:n where host-
              name  indicates  the host on which server and shell
              are running, and n is an  integer  >=1.  ssh2  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 unsecured (and will require the user  to
              manually  copy any required authorization cookies).


       HOME   The user's home directory.

       LOGNAME
              Synonym for USER; set for compatibility  with  sys-
              tems using this variable.

       MAIL   The user's mailbox.

       PATH   Set  to the default PATH, as specified when compil-
              ing ssh2 or, on some systems,  /etc/environment  or
              /etc/default/login.

       SSH_SOCKS_SERVER
              The format of this option is specified in ssh2_con-
              fig(5), option ProxyServer.

              Use of that option overrides this environment vari-
              able.  Normally,  use  of  an  environment variable
              would override the matching  configuration  option.
              The  reason  for this exceptional behaviour is his-
              torical.

              A default value for SSH_SOCKS_SERVER can be  speci-
              fied  at  compile  time by specifying --with-socks-
              server=VALUE on the  configure  command  line  when
              compiling ssh2.  The default value can be cancelled
              by setting SSH_SOCKS_SERVER to an empty string, and
              overridden  by  setting  SSH_SOCKS_SERVER  to a new
              value.

       SSH2_AUTH_SOCK
              If this exists, it is used to indicate the path  of
              a  Unix-domain  socket used to communicate with the
              authentication agent (or its local representative).

       SSH2_CLIENT
              Identifies  the  client end of the connection.  The
              variable  contains  three  space-separated  values:
              client  IP  address, client port number, and server
              port number.

       SSH2_ORIGINAL_COMMAND
              This will be the original command given to ssh2  if
              a  forced  command is run.  It can be used to fetch
              arguments and the like from the  other  end.   This
              does  not  have to be a real command, it can be the
              name of a  file,  device,  parameters  or  anything
              else.

       SSH2_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.

       TZ     The time-zone variable is set to indicate the  pre-
              sent  time  zone  if it was set when the daemon was
              started (the daemon passes the value to new connec-
              tions).

       USER   The name of the user.

       Additionally,     ssh2    reads    /etc/environment    and
       $HOME/.ssh2/environment, and adds lines of the format VAR-
       NAME=value  to  the  environment.   Some  systems may have
       still additional mechanisms for setting  up  the  environ-
       ment, such as /etc/default/login on Solaris.


FILES
       $HOME/.ssh2/random_seed
              Used for seeding the random number generator.  This
              file contains sensitive data  and  its  permissions
              should be 'read/write' for the user and 'not acces-
              sible' for others.  This file is created the  first
              time the program is run and it is updated automati-
              cally.  The user should never need to read or  mod-
              ify this file.

       $HOME/.ssh2/ssh2_config
              This  is the per-user configuration file.  The for-
              mat of this file is described above.  This file  is
              used  by  the ssh2 client.  This file does not usu-
              ally contain any  sensitive  information,  but  the
              recommended  permissions  are  'read/write' for the
              user, and 'not accessible' for others.

       $HOME/.ssh2/identification
              Contains information on  how  the  user  wishes  to
              authenticate when contacting a specific host.

              The identification file has the same general syntax
              as the configuration files.  The following keywords
              may be used:

       IdKey  This  is  followed by the filename of a private key
              in the $HOME/.ssh2 directory, used for  identifica-
              tion  when contacting a host. If there is more than
              one IdKey, they are tried in the  order  that  they
              appear in the identification file.

       PgpSecretKeyFile
              This  is  followed  by  the  filename of the user's
              OpenPGP private key ring in the $HOME/.ssh2  direc-
              tory.   OpenPGP  keys  listed  after  this line are
              expected to be found in this file.  Keys identified
              with  the IdPgpKey* keywords are used like the ones
              identified with the IdKey keyword.

       IdPgpKeyName
              This is followed by the OpenPGP key name of the key
              in PgpSecretKeyFile file.

       IdPgpKeyFingerprint
              This  is followed by the OpenPGP key fingerprint of
              the key in PgpSecretKeyFile file.

       IdPgpKeyId
              This is followed by the OpenPGP key ID of  the  key
              in PgpSecretKeyFile file.


       $HOME/.ssh2/authorization
              Contains  information on how the server will verify
              the identity of an user.

              The authorization file has the same general  syntax
              as the configuration files.  The following keywords
              may be used:

       Key    This is followed by the filename of a public key in
              the  $HOME/.ssh2 directory that is used for identi-
              fication when contacting the host. If there is more
              than one key, they are all acceptable for login.

       PgpPublicKeyFile
              This  is  followed  by  the  filename of the user's
              OpenPGP public key ring in the  $HOME/.ssh2  direc-
              tory.   OpenPGP  keys  listed  after  this line are
              expected to be found in this file.  Keys identified
              with  the  PgpKey*  keywords are used like the ones
              identified with the Key keyword.

       PgpKeyName
              This is followed by the OpenPGP key name.

       PgpKeyFingerprint
              This is followed by the OpenPGP key fingerprint.

       PgpKeyId
              This is followed by the OpenPGP key ID.

       Options
              This keyword, if used, must follow the Key or  Pgp-
              Key* keyword above.  The various options are speci-
              fied as a comma-separated list.  See  section  PUB-
              LIC-KEY OPTIONS for documentation of the options.

       Command
              This keyword is deprecated (though it still works),
              use Options instead.


       $HOME/.ssh2/hostkeys/key_xxxx_yyyy.pub
              These files are the public keys of  the  hosts  you
              connect   to.   These  are  updated  automatically,
              unless you have set StrictHostKeyChecking  to  yes.
              If a host's key changes, you should put the new key
              here.  Do not do this unless you can  be  sure  the
              key  is valid, i.e. no man-in-the-middle attack has
              occurred!  xxxx is the port  on  the  server  where
              sshd2  runs  and yyyy is the host (specified on the
              command line).

       /etc/ssh2/hostkeys/key_xxxx_yyyy.pub
              If a host key is not found in $HOME/.ssh2/hostkeys,
              this  is  the  next  location to be checked.  These
              files have to be updated manually.   No  files  are
              put here automatically.

       $HOME/.rhosts
              This  file  contains host-username pairs, separated
              by a whitespace, one per line.  The given  user  is
              permitted  to  log in from the given host without a
              password.  The same file is  used  by  rlogind  and
              rshd.  sshd2  differs from rlogind and rshd in that
              it requires public host-key authentication from the
              ssh2  server  running  on  this host in addition to
              validating the host name retrieved from domain name
              servers.   The  file  must  be writable only by the
              user; it is recommended that it is  not  accessible
              by others.

              It  is  also possible to use netgroups in the file.
              Either the hostname or username may be of the  form
              +@groupname  to  specify  all hosts or all users in
              the group.

       $HOME/.shosts
              For ssh2, this file is  exactly  the  same  as  for
              .rhosts.   However, this file is not used by rlogin
              and rshd, so using this permits access  using  ssh2
              only.

       /etc/hosts.equiv
              This  file  is  used during .rhosts authentication.
              In its simplest form, this file contains hostnames,
              one  per  line.  Users on those hosts are permitted
              to log in without a password,  provided  they  have
              the  same  username on both machines.  The hostname
              may also be followed by a username; such users  are
              permitted  to  log  in  as any user on this machine
              (except root).  Additionally,  the  syntax  +@group
              can  be used to specify netgroups.  Negated entries
              start with '-'.

              If the client host/user is successfully matched  in
              this  file,  login  is automatically permitted pro-
              vided that the client and server usernames are  the
              same.   Additionally, successful host-based authen-
              tication is normally required.  This file  must  be
              writable only by root; it is recommended that it be
              world-readable.

              Warning: It is almost never  a  good  idea  to  use
              usernames in hosts.equiv. Note that it really means
              that the named  user(s)  can  log  in  as  anybody,
              including bin, daemon, adm, and other accounts that
              own critical binaries  and  directories.   Using  a
              username  practically  grants the user root access.
              The only valid use for usernames should be in nega-
              tive  entries.  Note that this warning also applies
              to rsh/rlogin.

       /etc/shosts.equiv
              This  is  processed  exactly  as  /etc/hosts.equiv.
              However,  this file is not used by rlogin and rshd,
              so using this permits access using ssh2 only.

       $HOME/.ssh2/knownhosts/xxxxyyyy.pub
              These are the public host keys of hosts that a user
              wants to log in from using hostbased authentication
              (equivalent to  RhostsRSAAuthentication  in  ssh1).
              Also,  users  have  to  set  up their $HOME/.shosts
              (only used by ssh) or  $HOME/.rhosts  files  (inse-
              cure, as it is used by the /fBr*/fR commands also).
              If the username is the same on both  hosts,  it  is
              adequate   to   put   the   public   host   key  to
              /etc/ssh2/knownhosts  and  add  the   hostname   to
              /etc/shosts.equiv (or /etc/hosts.equiv).

              xxxx  denotes the host name (FQDN) and yyyy denotes
              the public-key algorithm of the key.

              For  example,  if   the   host-key   algorithm   of
              zappa.foo.fi  is ssh-dss, the host key is contained
              in the file zappa.foo.fi.ssh-dss.pub in the  known-
              hosts directory.

              Possible  names  for public-key algorithms are ssh-
              dss and ssh-rsa.


       /etc/ssh2/knownhosts/xxxxyyyy.pub
              As above, but system-wide.  These settings  can  be
              overridden  by  the user by putting a file with the
              same name to the $HOME/.ssh2/knownhosts  directory.

PUBLIC-KEY OPTIONS
       Options are specified as a comma-separated list.

       allow-from and deny-from
              In   addition  to  public-key  authentication,  the
              canonical name of the remote host  must  match  the
              given  pattern(s).   These  parameters  follow  the
              logic of {Allow,Deny}Hosts, described in detail  in
              sshd2_config(5).   Specify one pattern per keyword;
              multiple keywords can be used.  See Examples below.

       command="command"
              This  is  used  to  specify a "forced command" that
              will be executed on the server side instead of any-
              thing  else  when  the  user is authenticated.  The
              command supplied by the user (if any) is put in the
              environment  variable  SSH2_ORIGINAL_COMMAND.   The
              command is run on a pty if the connection  requests
              a  pty;  otherwise it is run without a tty.  Quotes
              may be used in the command if  escaped  with  back-
              slashes.

              This option might be useful for restricting certain
              public keys to perform just a  specific  operation.
              An example might be a key that permits remote back-
              ups but nothing else.  Notice that the  client  may
              specify  TCP/IP  and/or X11 forwarding, unless they
              are explicitly prohibited (see no-port-forwarding).

       environment="NAME=value"
              Specifies  that  the  string  is to be added to the
              environment when logging in using this key.   Envi-
              ronment  variables  set  this  way  override  other
              default environment values.   Multiple  options  of
              this type are permitted.

       idle-timeout=time
              Sets  idle  timeout limit to time either in seconds
              (s or nothing after the number), in minutes (m), in
              hours  (h),  in  days  (d), or in weeks (w). If the
              connection has been idle (all channels) this  long,
              the connection is closed.

       no-port-forwarding
              Forbids TCP/IP forwarding when this key is used for
              authentication.  Any port forward requests  by  the
              client  will  return  an  error.  This is useful in
              combination with the command option.

       no-x11-forwarding
              Forbids X11 forwarding when this key  is  used  for
              authentication.   Any  X11  forward requests by the
              client will return an error.

       no-agent-forwarding
              Forbids authentication agent forwarding  when  this
              key is used for authentication.

       no-pty Prevents  tty  allocation  (a request to allocate a
              pty will fail).


   Examples
       Options      allow-from=".*\.niksula\.hut\.fi",      deny-
       from="pc\.niksula\.hut\.fi"

       Options  command="echo  $SSH2_ORIGINAL_COMMAND $FOO $BAR",
       environment="FOO=zuppa",  environment="BAR=zappa",  allow-
       from="kungfoo.org", allow-from="linux.com"


EXIT VALUES
       On  normal  execution,  ssh2  exits with the status of the
       command run. On successful runs this is normally 0 (zero).

       If ssh2 encounters an error, you usually see the reason in
       an error message. However, accommodating for that in  e.g.
       batch  files  is  difficult, so some usual exit values for
       ssh2 are documented here.  Note that the command you  have
       run  may also return the same exit values.  Unfortunately,
       little can be done to avoid this, as the exit value  space
       is so small (8 bits).


       128 + signal number
              This is returned if ssh2 encounters a fatal signal.
              E.g. 143 would be returned for SIGTERM (signal num-
              ber 15).

       64 + disconnect code
              This is returned on disconnect, clean or otherwise.

                     host not allowed to connect      1
                     protocol error                   2
                     key exchange failed              3
                     reserved                         4
                     MAC error                        5
                     compression error                6
                     service not available            7
                     protocol version not supported   8
                     host key not verifiable          9
                     connection lost                 10
                     by application                  11
                     too many connections            12
                     auth cancelled by user          13
                     no more auth methods available  14
                     illegal user name               15

              E.g. 74 would mean 'Connection lost'.

       -1     Returned on a call for ssh_fatal().

       254    Usually means that ssh2 failed to exec(3) something
              (generic catch-all in the libraries for failures to
              fork(2) or exec(3)).

       1      Generic error, usually because invalid command-line
              options or malformed configuration.

       2      Connecting to remote host failed.


       Note that when the command is run from JCL using BPXBATCH,
       the exit values are multiplied by 256.


AUTHORS
       SSH Communications Security Corp.

       For more information, see http://www.ssh.com.


SEE ALSO
       ssh2_config(5), sshd2(8), sshd2_config(5), ssh-keygen2(1),
       ssh-agent2(1),  ssh-add2(1), scp2(1), sftp2(1), rlogin(1),
       rsh(1), telnet(1)

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