hlfsd - home-link file system daemon


SYNOPSIS

       hlfsd  [  -fhnpvC ] [ -a alt_dir ] [ -c cache-interval ] [
       -g group ] [ -i reload-interval ] [  -l  logfile  ]  [  -o
       mount-options  ] [ -x log-options ] [ -D debug-options ] [
       -P password-file ] [ linkname [ subdir ] ]


DESCRIPTION

       Hlfsd is a daemon which implements a filesystem containing
       a  symbolic  link  to  subdirectory  within  a user's home
       directory, depending on the user which accessed that link.
       It  was  primarily  designed  to redirect incoming mail to
       users' home directories, so that it  can  read  from  any­
       where.

       Hlfsd operates by mounting itself as an NFS server for the
       directory   containing   linkname,   which   defaults   to
       /hlfs/home.   Lookups within that directory are handled by
       hlfsd, which uses the password map  to  determine  how  to
       resolve  the  lookup.  The directory will be created if it
       doesn't already exist.  The symbolic link will be  to  the
       accessing  user's  home directory, with subdir appended to
       it.  If not specified, subdir defaults to .hlfsdir.   This
       directory  will  also  be  created  if it does not already
       exist.

       A SIGTERM sent to hlfsd will  cause  it  to  shutdown.   A
       SIGHUP  will  flush  the  internal  caches, and reload the
       password map.  It will also close and reopen the log file,
       to  enable the original log file to be removed or rotated.
       A SIGUSR1 will cause it to dump its internal table of user
       IDs     and     home     directories     to    the    file
       /usr/tmp/hlfsd.dump.XXXXXX.


OPTIONS

       -a alt_dir
              Alternate directory.  The name of the directory  to
              which  the  symbolic  link  returned  by hlfsd will
              point, if it cannot access the  home  directory  of
              the user.  This defaults to /var/hlfs.  This direc­
              tory will be created  if it doesn't exist.   It  is
              expected  that  either users will read these files,
              or the system administrators will run a  script  to
              resend this "lost mail" to its owner.

       -c cache-interval
              Caching interval.  Hlfsd will cache the validity of
              home directories for  this  interval,  in  seconds.
              Entries  which  have  been verified within the last
              cache-interval seconds will not be verified  again,
              since  the  operation  could  be expensive, and the
              entries are most likely  still  valid.   After  the

              validity of the user's home  directory,  and  reset
              the  cache  time-counter.   The  default  value for
              cache-interval is 300 seconds (5 minutes).

       -f     Force fast startup.  This  option  tells  hlfsd  to
              skip  startup-time consistency checks such as exis­
              tence of mount directory,  alternate  spool  direc­
              tory,  symlink  to be hidden under the mount direc­
              tory, their permissions and validity.

       -g group
              Set the special group HLFS_GID to group.   Programs
              such  as from or comsat, which access the mailboxes
              of other users) must be  setgid  HLFS_GID  to  work
              properly.   The  default  group  is  "hlfs".  If no
              group is provided, and there is  no  group  "hlfs",
              this feature is disabled.

       -h     Help.  Print a brief help message, and exit.

       -i reload-interval
              Map-reloading  interval.  Each reload-interval sec­
              onds, hlfsd will reload the  password  map.   Hlfsd
              needs the password map for the UIDs and home direc­
              tory  pathnames.   Hlfsd  schedules  a  SIGALRM  to
              reload  the  password maps.  A SIGHUP sent to hlfsd
              will force it to reload the maps immediately.   The
              default  value  for  reload-interval is 900 seconds
              (15 minutes.)

       -l logfile
              Specify a log  file  to  which  hlfsd  will  record
              events.   If  logfile is the string syslog then the
              log messages will be sent to the system log  daemon
              by  syslog(3), using the LOG_DAEMON facility.  This
              is also the default.

       -n     No verify.  Hlfsd will not verify the  validity  of
              the symbolic link it will be returning, or that the
              user's home  directory  contains  sufficient  disk-
              space for spooling.  This can speed up hlfsd at the
              cost of possibly returning symbolic links  to  home
              directories  which  are not currently accessible or
              are full.  By default,  hlfsd  validates  the  sym­
              bolic-link  in the background.  The -n option over­
              rides the  meaning  of  the  -c  option,  since  no
              caching is necessary.

       -o mount-options
              Mount  options.  Mount options which hlfsd will use
              to mount itself on top  of  dirname.   By  default,
              mount-options  is  set to "ro".  If the system sup­
              ports symbolic-link caching,  default  options  are


       -p     Print  PID.   Outputs  the  process-id  of hlfsd to
              standard output where it can be saved into a  file.

       -v     Version.   Displays version information to standard
              error.

       -x log-options
              Specify run-time logging options.  The options  are
              a  comma  separated list chosen from: fatal, error,
              user, warn, info, map, stats, all.

       -C     Force hlfsd to run on systems that cannot turn  off
              the  NFS  attribute-cache.   Use  of this option on
              those systems is discouraged, as it may  result  in
              loss or misdelivery of mail.  The option is ignored
              on systems that can turn off the attribute-cache.

       -D log-options
              Select from a variety of debugging  options.   Pre­
              fixing  an  option  with the string no reverses the
              effect of that  option.   Options  are  cumulative.
              The  most  useful option is all.  Since this option
              is only used for debugging other  options  are  not
              documented here.  A fuller description is available
              in the program source.  A  SIGUSR1  sent  to  hlfsd
              will  cause it to dump its internal password map to
              the file /usr/tmp/hlfsd.dump.XXXXXX.

       -P password-file
              Read the user-name,  user-id,  and  home  directory
              information from the file password-file.  Normally,
              hlfsd will use getpwent(3)  to  read  the  password
              database.   This  option allows you to override the
              default database, and is useful if you want to  map
              users'  mail  files to a directory other than their
              home directory.  Only the username, uid, and  home-
              directory fields of the file password-file are read
              and checked.  All other fields  are  ignored.   The
              file password-file must otherwise be compliant with
              Unix System 7 colon-delimited format passwd(4).


FILES

       /hlfs
            directory under which hlfsd mounts itself and manages
            the symbolic link home.
       .hlfsdir
            default  sub-directory  in the user's home directory,
            to which the home symbolic  link  returned  by  hlfsd
            points.
       /var/hlfs
            directory  to  which  home  symbolic link returned by
            hlfsd points if it  is  unable  to  verify  the  that


SEE ALSO

       amd(8),  automount(8),  cron(8), getgrent(3), getpwent(3),
       mail(1), mnttab(4), mount(8),  mtab(5),  passwd(4),  send­
       mail(8), umount(8).
       HLFSD:  Delivering Email to Your $HOME, in Proc. LISA-VII,
       The 7th Usenix System Administration Conference,  November
       1993.

AUTHORS

       Erez Zadok <ezk@cs.columbia.edu>, Computer Science Depart­
       ment, Columbia University, New York City, New  York,  USA,
       and  Alexander Dupuy <dupuy@smarts.com>, System Management
       ARTS, White Plains, New York, USA.


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