DMTCP preserves the original pre-checkpoint environment variables when
it restarts.  Usually, this is the desired behavior.  In a few cases,
one wishes to update the environment variables based on their values
within the parent process of the restarted process.  These updates
can be specified in a file:
  dmtcp_env.txt
The file dmtcp_env.txt must be in the same checkpoint directory as
the checkpoint image files ( ckpt_*.dmtcp ).

For example, one might wish to update $DISPLAY, based on the environment
at the time of restart.  To do this, add a file, dmtcp_env.txt, in the
current directory with the line:

DISPLAY=$DISPLAY

It would then be up to the target application to call getenv("DISPLAY")
one more time.  This could be done within the target application, or
else the target application writer might choose to create an additional
plugin (loaded after this one), which copies getenv("DISPLAY")
to a global variable at the time of restart.

To demonstrate, do:
  make check

The file dmtcp_env.txt should illustrate the syntax and usage.

WARNING:  Do not disable the built-in malloc plugin when using this,
  or else there will be a danger of deadlock at the time of restart
  due to a lock in libc_malloc.
    (In rare cases of highly malloc-intensive probrams, users sometimes
  disable the built-in malloc plugin to avoid overhead.  In the future,
  this source of overhead will be eliminated, so that no user need disable
  the malloc plugin.)



