MAN page from RedHat EL 8 am-utils-6.2.0-38.el8.x86_64.rpm


Section: Maintenance Commands (8)
Updated: 14 September 1993


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 ]] 


Hlfsdis a daemon which implements a filesystem containing a symbolic link tosubdirectory within a user's home directory, depending on the userwhich accessed that link. It was primarily designed to redirectincoming mail to users' home directories, so that it can read fromanywhere.

Hlfsdoperates by mounting itself as anNFSserver for the directory containinglinkname,which defaults to/hlfs/home.Lookups within that directory are handled byhlfsd,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, withsubdirappended to it. If not specified,subdirdefaults to.hlfsdir.This directory will also be created if it does not already exist.

A SIGTERM sent tohlfsdwill cause it to shutdown. A SIGHUP will flush the internalcaches, and reload the password map. It will also close andreopen the log file, to enable the original log file to beremoved or rotated. A SIGUSR1 will cause it to dump its internaltable 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 whichthe symbolic link returned byhlfsdwill point, if it cannot access the home directory of the user. Thisdefaults to/var/hlfs.This directory will be created if it doesn't exist. It is expectedthat either users will read these files, or the system administratorswill run a script to resend this "lost mail" to its owner.
-c cache-interval
Caching interval.Hlfsdwill cache the validity of home directories for this interval, inseconds. Entries which have been verified within the lastcache-intervalseconds will not be verified again, since the operation couldbe expensive, and the entries are most likely still valid.After the interval has expired,hlfsdwill re-verify the validity of the user's home directory, andreset the cache time-counter. The default value forcache-intervalis 300 seconds (5 minutes).
Force fast startup. This option tellshlfsdto skip startup-time consistency checks such as existence of mountdirectory, alternate spool directory, symlink to be hidden under themount directory, their permissions and validity.
-g group
Set the special group HLFS_GID togroup.Programs such asfromorcomsat,which access the mailboxes of other users) must be setgid HLFS_GID towork properly. The default group is "hlfs". If no group is provided,and there is no group "hlfs", this feature is disabled.
Help. Print a brief help message, and exit.
-i reload-interval
Map-reloading interval. Eachreload-intervalseconds,hlfsdwill reload the password map.Hlfsdneeds the password map for the UIDs and home directory pathnames.Hlfsdschedules a SIGALRM to reload the password maps. A SIGHUP sent tohlfsdwill force it to reload the maps immediately. The defaultvalue forreload-intervalis 900 seconds (15 minutes.)
-l logfile
Specify a log file to whichhlfsdwill record events. Iflogfileis the stringsyslogthen the log messages will be sent to the system log daemon bysyslog(3),using the LOG_DAEMON facility.This is also the default.
No verify.Hlfsdwill not verify the validity of the symbolic link it will bereturning, or that the user's home directory containssufficient disk-space for spooling. This can speed uphlfsdat the cost of possibly returning symbolic links to homedirectories which are not currently accessible or are full.By default,hlfsdvalidates the symbolic-link in the background.The-noption overrides the meaning of the-coption, since no caching is necessary.
-o mount-options
Mount options. Mount options whichhlfsdwill use to mount itself on top ofdirname.By default,mount-optionsis set to "ro". If the system supports symbolic-link caching, defaultoptions are set to "ro,nocache".
Print PID.Outputs the process-id ofhlfsdto standard output where it can be saved into a file.
Version. Displays version information to standard error.
-x log-options
Specify run-time logging options. The options are a comma separatedlist chosen from: fatal, error, user, warn, info, map, stats, all.
Forcehlfsdto run on systems that cannot turn off the NFS attribute-cache. Use ofthis option on those systems is discouraged, as it may result in lossor mis-delivery of mail. The option is ignored on systems that can turnoff the attribute-cache.
-D log-options
Select from a variety of debugging options. Prefixing anoption with the stringnoreverses the effect of that option. Options are cumulative.The most useful option isall.Since this option is only used for debugging other options are notdocumented here. A fuller description is available in the programsource. A SIGUSR1 sent tohlfsdwill 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 filepassword-file.Normally,hlfsdwill usegetpwent(3)to read the password database. This option allows you to override thedefault database, and is useful if you want to map users' mail files to adirectory other than their home directory. Only the username, uid, andhome-directory fields of the filepassword-fileare read and checked. All other fields are ignored. The filepassword-filemust otherwise be compliant with Unix System 7 colon-delimited formatpasswd(4).


directory under whichhlfsdmounts itself and manages the symbolic linkhome.
default sub-directory in the user's home directory, to which thehomesymbolic link returned byhlfsdpoints.
directory to whichhomesymbolic link returned byhlfsdpoints if it is unable to verify the thatuser's home directory is accessible.



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


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


Erez Zadok <>, Computer Science Department, Stony BrookUniversity, Stony Brook, New York, USA.andAlexander Dupuy <>, System Management ARTS,White Plains, New York, USA.Other authors and contributors to am-utils are listed in theAUTHORSfile distributed with am-utils.




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