Provided by: devfsd_1.3.25-23_i386 bug

NAME

       devfsd   -  optional  daemon  for  managing  devfs  (the  Linux  Device
       Filesystem)

SYNOPSIS

       devfsd mntpnt [ -v ] [ -d ] [ -t num ] [ -D mask ] [ -fg ] [ -np ]

DESCRIPTION

       The devfsd programme is a daemon, run by the system boot scripts, which
       can  provide for intelligent management of device entries in the Device
       Filesystem (devfs).  It  is  desirable  to  start  the  daemon  at  the
       beginning  of the boot scripts, in particular before filesystem checks.

       As part of its setup phase devfsd creates certain symbolic links  which
       are   compiled   into   the   code.   These   links   are  required  by
       /usr/src/linux/Documentation/devices.txt. This behaviour may change  in
       future revisions.

       devfsd  will  read the special control file .devfsd in a mounted devfs,
       listening for the creation and  removal  of  device  entries  (this  is
       termed  a change operation). For each change operation, devfsd can take
       many actions. The daemon will normally run itself in the background and
       send messages to syslog.

       The  opening  of  the  syslog  service  is  automatically delayed until
       /dev/log is created.

       At startup, before switching to  daemon  mode,  devfsd  will  scan  the
       mounted  device  tree  and  will generate synthetic REGISTER events for
       each leaf node and directory.

OPTIONS

       mntpnt This specifies a mount point for where devfs is mounted. This is
              typically "/dev". The daemon will change directory to this mount
              point before opening any files.

       -v     This option will print the protocol version numbers  for  devfsd
              and  the  kernel-side protocol version provided by devfs itself.
              The programme then exits.

       -d     Run devfsd in debug mode. Used  for  debugging  the  kernel-side
              protocol  implemented  by  devfs.  This also prints the protocol
              version numbers. In this mode the daemon runs in the foreground.

       -t num Set  the trace level to num. If the level is greater than 0 then
              output is sent to stderr rather than syslog(3). If the level  is
              greater than 1 then devfsd will run in trace mode. Higher levels
              yield more trace information.

       -D mask
              Set the debug mask for devfs.

       -fg    Run the daemon in the foreground.

       -np    Exit  after  parsing  the  configuration  file  and   processing
              synthetic  REGISTER  events.  Do  not  poll  for events. This is
              primarily  used  for  creating  compatibility  entries   without
              needing a daemon running in the background.

CONFIGURATION

       The  configuration  file  /etc/devfs/devfsd.conf  configures the devfsd
       programme. It is a simple ASCII file with one configuration option  per
       line.  Comment  lines  must start with a leading ’#’ character. Comment
       lines and blank lines are  ignored.  Each  configuration  option  is  a
       keyword  followed  by zero or more parameters, depending on the option.
       The following section details the configuration options. Below are  the
       permitted keywords:

       INCLUDE location
              Include  the  configuration  file  named  by  location. Variable
              expansion is applied to location (see the  section  on  VARIABLE
              EXPANSION below). If this is a directory, then all files (except
              those which start with ’.’) are read. This  is  recursive  (i.e.
              files which are in fact subdirectories are also read).

              If  the  first  character  of  location is "+", then the rest of
              location is the name of an NIS map to load.  This  operation  is
              silently  ignored if the NIS domain has not yet been set (SIGHUP
              should then be sent after the NIS domain has been set).

       OPTIONAL_INCLUDE location
              As above, except that if the file does not exist, it is silently
              ignored.

       CLEAR_CONFIG
              Clear the current configuration.

       RESTORE directory
              This  will  restore  entries previously saved under directory to
              devfs. Only symbolic links or entries with the  sticky  bit  set
              will be restored. This action is taken as the configuration file
              is read. With appropriate COPY actions, complete persistence  is
              acheived.

       The  config  file  can  also  be used to specify actions that should be
       taken at specified events. Each line specifies  an  event  and  action.
       Multiple  actions  (of  the  same  or different types) per event may be
       specified (one action per line). Events are processed  in  order,  with
       the first event config line being processed first. The syntax is:

       EVENT devname ACTION [args...]
              where  EVENT  is the event and ACTION is the action to take when
              the event occurs. The action is only taken when devname  matches
              the name of the device entry affected (this does not include the
              mount point for the filesystem). This is processed as a  regular
              expression.  Some  actions  support  extra  arguments, passed as
              args.

              Variable expansion is applied to the arguments (see the  section
              on  VARIABLE EXPANSION below). After variable expansion, regular
              expression substitution is performed (see the section on REGULAR
              EXPRESSION   SUBSTITUTION).  Note  that  the  following  special
              variable names are also recognised:

              devpath
                     the full path name of the new device

              devname
                     the name of the new device inside the devfs namespace

              mode   the mode of the device entry in octal

              uid    the user ID of the process or inode

              gid    the group ID of the process or inode

       The following events are recognised:

       REGISTER
              The device entry or directory was registered by a device driver.

       UNREGISTER
              The device entry was unregistered by a device driver.

       ASYNC_OPEN
              The  inode  was  opened (the opening process does not wait for a
              response).

       CLOSE  The file was closed.

       LOOKUP An inode lookup was performed and there  was  no  device  entry.
              This  event  is  not sent if the initiating process is devfsd or
              one of its children.

       CHANGE Some inode attributes were changed.

       CREATE An inode was created by a process.

       DELETE An inode was deleted by a process.

       The following actions are recognised:

       PERMISSIONS owner_and_group access_mode
              owner_and_group specifies the owner  and  group  that  the  file
              should  be  set  to.  This  must be of the form "user.group" and
              either "user" or "group" component may be symbolic  or  numeric.
              To  specify  that the user or group be left alone, use a numeric
              value  of  "-1"  for  the  respective   component.   access_mode
              specifies  the  access mode the file should be set to. This must
              be either an octal value or a symbolic string of nine characters
              with  the  form  "rwxrwxrwx".  Where  access is not given, a ’-’
              character should be used in place (e.g. "rw-rw-r--"  gives  read
              and  write  access to the user and group and only read access to
              everybody else).

       MODLOAD
              This action will pass "/dev/$devname" (i.e. "/dev/" prefixed  to
              the  device  name)  to the module loading facility. In addition,
              the /etc/modutils/devfs configuration file is used.

       EXECUTE path [arg...]
              This action allows you to run a programme. path is the  pathname
              of  the  programme to run and arg is a set of optional arguments
              passed to the programme (maximum 6). path is the first  argument
              (i.e. argv[0]) passed to the programme.

       MFUNCTION path function [arg...]
              This  action  allows you to run a "main"-style function within a
              shared object. path is the pathname of the shared  object,  with
              the special path of "GLOBAL" signifying all global symbols (e.g.
              from libc). The default directory is  /lib/devfsd.  function  is
              the  name  of  the  function  symbol  to run and arg is a set of
              optional arguments passed to the function (maximum 5).  path  is
              the  first  argument  (i.e. argv[0]) passed to the function. The
              prototype for this function is similar to the main function of C
              programmes. The prototype is:

              int func (int argc, char **argv);

       CFUNCTION path function [arg...]
              This  action  is similar to the MFUNCTION action, except for the
              calling convention. The prototype for this function is:

              int func (void *arg1, void *arg2, void *arg3, void  *arg4,  void
              *arg5);

              Up  to 5 arguments may be passed, each being of type void *. The
              following special arguments are recognised:

              EVENT  a struct devfsd_notify_struct * is passed

       COPY source destination
              This action will copy the device type and permissions of  source
              to  destination.  The sticky bit is set on the destination inode
              if the source inode was create manually (i.e. not by a driver or
              devfsd).

       IGNORE This action causes all subsequent processing for the event to be
              ignored.

       MKOLDCOMPAT
              This action creates an "old" compatibility entry for the device.

       MKNEWCOMPAT
              This  action creates a "new" compatibility entry for the device.

       RMOLDCOMPAT
              This action removes an "old" compatibility entry for the device.

       RMNEWCOMPAT
              This  action removes a "new" compatibility entry for the device.

VARIABLE EXPANSION

       A subset of normal  Bourne  shell  variable  expansion  is  applied  to
       various  expressions.  The  currently  supported  subset is: $variable,
       ${variable}  and  ${variable:-word}.   Variables  are  taken  from  the
       environment. The following variable names are also defined :

       hostname
              The hostname of the machine

       mntpnt The mount point for devfs

REGULAR EXPRESSION SUBSTITUTION

       Sections  of  the  matched  regular  expression  can  be included in an
       action.  Use \0 to refer to the entire regular expression  matched,  \1
       to  refer  to the first parenthesized subexpression, \2 to refer to the
       second, and so on.  (Use \\ to include an actual backslash.)

       See devfsd.conf(5) for examples of regular expression substitution.

SIGNALS

       devfsd responds to signals in a variety of ways:

       SIGINT devfsd will exit cleanly.

       SIGTERM
              devfsd will exit cleanly.

       SIGHUP The configuration file is re-read and  any  shared  objects  are
              reloaded.  Then the mounted device tree is scanned and synthetic
              REGISTER events are generated for each leaf node.

       SIGUSR1
              The configuration file is re-read and  any  shared  objects  are
              reloaded. No synthetic REGISTER events are generated.

EXAMPLES

       Create and destroy old compatibility entries:
              REGISTER     .*           MKOLDCOMPAT
              UNREGISTER   .*           RMOLDCOMPAT

       Create and destroy new compatibility entries:
              REGISTER     .*           MKNEWCOMPAT
              UNREGISTER   .*           RMNEWCOMPAT

       Load modules:
              LOOKUP       .*           MODLOAD

       Make and remove a symbolic link:
              REGISTER     mydir/mydev  CFUNCTION GLOBAL mksymlink $devname mydev
              UNREGISTER   mydir/mydev  CFUNCTION GLOBAL unlink  mydev

       Give sndusers group access to sound drivers

              REGISTER     sound/.*     PERMISSIONS root.sndusers rw-rw----

FILES

       /etc/devfs/devfsd.conf
              the  configuration  file.  If  this  file is missing or has zero
              size, devfsd will exit after its setup phase.

       /etc/modutils/devfs
              the generic module configuration file (required for the  MODLOAD
              action),  which  is installed with devfsd. This in turn includes
              /etc/modules.conf

CAVEATS

       Make  sure  you  understand  the  implications  of  regular  expression
       matching. For example, if you had a configuration line such as:

       LOOKUP   cdrom   CFUNCTION   GLOBAL  mksymlink  ${mntpnt}/cdroms/cdrom0
       $devpath

       then  referencing  "/dev/cdrom1"  will   create   the   symbolic   link
       "/dev/cdrom1".  Further,  referencing "/dev/cdroms/1" would also create
       the "/dev/cdroms/1" symbolic link. This is probably not what you  want.
       If  there was not already a "/dev/cdroms" directory, then you would get
       a "/dev/cdrom" symbolic  link.  Definately  not  what  you  want!   The
       correct configuration line would be:

       LOOKUP   ^cdrom$  CFUNCTION  GLOBAL  mksymlink  ${mntpnt}/cdroms/cdrom0
       $devpath

SEE ALSO

       init(8), devfsd.conf(5), modprobe(8)

AUTHOR

       Richard Gooch (rgooch@atnf.csiro.au)

AVAILABILITY

       The     Device     Filesystem     daemon     is     available     from:
       http://www.atnf.csiro.au/~rgooch/linux/

FURTHER READING

       It  is  strongly  recommended  to  read  the  devfs FAQ, which contains
       configuration       tips.       It       is        available        at:
       http://www.atnf.csiro.au/~rgooch/linux/docs/devfs.html

MAILING LIST

       A  mailing  list  exists  for  devfs  kernel  patch  and devfsd release
       announcements. This list also has a small amount of discussion  traffic
       (a  few  messages  per week). You may subscribe by sending a message to
       majordomo@oss.sgi.com with subscribe devfs in the message body.