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       hlfsd - home-link file system daemon


       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
       ] ]


       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

       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.


       -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 directory 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 interval has
              expired, hlfsd will re-verify 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 existence of mount directory,
              alternate spool directory, symlink to be hidden under the  mount
              directory, 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  seconds, hlfsd
              will reload the password map.  Hlfsd needs the password map  for
              the  UIDs  and  home  directory  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 symbolic-link  in  the  background.
              The  -n  option overrides 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  supports  symbolic-link  caching,  default
              options are set to "ro,nocache".

       -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 mis-delivery  of  mail.
              The  option  is  ignored  on  systems  that  can  turn  off  the

       -D log-options
              Select from a variety of debugging options.  Prefixing 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

       -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).


            directory under which hlfsd mounts itself and manages the symbolic
            link home.

            default sub-directory in the user’s home directory, to  which  the
            home symbolic link returned by hlfsd points.

            directory  to which home symbolic link returned by hlfsd points if
            it  is  unable  to  verify  the  that  user’s  home  directory  is


       amd(8),   automount(8),  cron(8),  getgrent(3),  getpwent(3),  mail(1),
       mnttab(4), mount(8), mtab(5), passwd(4), sendmail(8), umount(8).

       HLFSD: Delivering Email to Your  $HOME,  in  Proc.  LISA-VII,  The  7th
       Usenix System Administration Conference, November 1993.

       ‘‘am-utils’’ info(1) entry.

       Linux   NFS   and   Automounter  Administration  by  Erez  Zadok,  ISBN
       0-7821-2739-8, (Sybex, 2001).


       Erez Zadok  <>,  Computer  Science  Department,  Stony
       Brook  University,  Stony  Brook,  New  York, USA.  and Alexander Dupuy
       <>, System Management ARTS,  White  Plains,  New  York,

       Other  authors  and  contributors to am-utils are listed in the AUTHORS
       file distributed with am-utils.

                               14 September 1993