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.
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
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.
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.
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.)
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.
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.
Specify run-time logging options. The options are a comma
separated list chosen from: fatal, error, user, warn, info, map,
-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
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
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
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 <email@example.com>, Computer Science Department, Stony
Brook University, Stony Brook, New York, USA. and Alexander Dupuy
<firstname.lastname@example.org>, 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