NAME

       vlock - Virtual Console lock program

SYNOPSIS

       vlock [ -hv ]

       vlock [ -acns ] [ -t <timeout> ] [ plugins... ]

DESCRIPTION

       vlock  is  a  program  to  lock one or more sessions on the Linux console.  This is especially useful for
       Linux machines which have multiple users with access to the console.   One  user  may  lock  his  or  her
       session(s) while still allowing other users to use the system on other virtual consoles.  If desired, the
       entire console may be locked and virtual console switching disabled.

       By default, only the current VC (virtual console) is locked.   With  the  -a,--all  option  all  VCs  are
       locked.  The locked VCs cannot be unlocked without the invoker's password or the root password.  The root
       password will always be able to unlock any or all sessions, unless disabled at compile time.

       Please note that it is entirely possible to completely lock yourself out of the console with the -a,--all
       option  if  you  cannot remember your password!  Unless you are able to kill vlock by logging in remotely
       via a serial terminal or network, a hard reset is the only method of ``unlocking'' the display.

       When locking the entire console display it is sometimes still possible to kill  vlock  using  the  Secure
       Access  Key  (SAK)  or  other  commands  that  are  available  through  the  SysRq  mechanism.   When the
       -s,--disable-sysrq and -a,--all options are given the SysRq mechanism is disabled while vlock is running.
       See /usr/src/linux/Documentation/sysrq.txt for more details.

       vlock works for console sessions primarily.  To lock the entire console display from an X session use the
       -n,--new option.  This will make vlock switch to an empty virtual console to lock the display.

       The options -n,--new, -s,--disable-sysrq, and -t,--timeout only work if vlock  is  compiled  with  plugin
       support.  See the PLUGINS section for more information.

OPTIONS

       -a,--all

              Lock all console sessions and disable VC switching.

       -c,--current

              Lock the current session (this is the default).

       -n,--new

              Switch to a new virtual console before locking all console sessions.

       -s,--disable-sysrq

              Disable  the  SysRq  mechanism  while consoles are locked.  This option only works if the -a,--all
              option given.

       -t,--timeout <seconds>

              Specify the timeout for the screensaver plugins.  See vlock-plugins(5) for more information.

       -h,--help

              Print a brief help message.

       -v,--version

              Print the version number.

ENVIRONMENT VARIABLES

       The following environment variables can be used to change vlock's behavior:

       USER

              If this variable is when vlock is run as root (uid 0) vlock locks the screen as this user  instead
              of  root.   The root password will still be able to unlock the session, unless disabled at compile
              time.

       VLOCK_ALL_MESSAGE

              If this variable is set and all consoles are locked its contents  will  be  used  as  the  locking
              message instead of the default message.

       VLOCK_CURRENT_MESSAGE

              If  this  variable is set and only the current consoles is locked its contents will be used as the
              locking message instead of the default message.

       VLOCK_MESSAGE

              If this variable is set its contents will be used as the locking message instead of  the  default.
              This overrides the former two variables.

       VLOCK_PLUGINS

              If this variable is set it is interpreted as a space separated list of plugins that will be loaded
              when vlock starts additionally to the ones listed on the command line.

       VLOCK_TIMEOUT

              Set this variable to specify the timeout (in seconds) after which the  screen  saver  plugins  (if
              any)  will  be  invoked.   If this variable is unset or set to an invalid value or 0 no timeout is
              used.  See vlock-plugins(5) for more information about plugins.

       VLOCK_PROMPT_TIMEOUT

              Set this variable to specify the amount of time (in seconds) you will have to enter your  password
              at  the  password prompt.  If this variable is unset or set to an invalid value or 0 no timeout is
              used.  Warning: If this value is too low, you may not be able to unlock your session.

FILES

       ~/.vlockrc

              This file is read by vlock on startup if it exists.  All the variables mentioned above can be  set
              here.

SECURITY

       See the SECURITY file in the vlock distribution for more information.

SEE ALSO

       vlock-main(8), vlock-plugins(5)

AUTHORS

       Michael K. Johnson <http://danlj.org/mkj/>

       Frank Benkstein <frank-vlock@benkstein.net>