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NAME    [Toc]    [Back]

       uucp_intro - UNIX-to-UNIX Copy Program (UUCP) introductory

DESCRIPTION    [Toc]    [Back]

       The UNIX-to-UNIX Copy Program (UUCP) is a  group  of  programs
  that  support  communications between two computers
       running UNIX operating systems.

       Tru64 UNIX supports the HoneyDanBer version of UUCP.   The
       UUCP  system enables batched, error-free file transfer and
       remote command execution between  two  UNIX  systems.  The
       UUCP system is most frequently used to transfer electronic
       mail, network news, and public domain software  over  lowspeed,
 low-cost communications links.

       A  worldwide  network  that functions through the informal
       cooperation of the user  community  has  grown  up  around
       UUCP.  The  UUCP  network  is  a  series of point-to-point
       links, with the majority of sites located  in  Europe  and
       North America.

       The  UUCP protocol itself supports only direct connections
       between two systems.  However, electronic  news  and  mail
       delivery  depend on third-party forwarding.  To facilitate
       mail and news delivery, most connected sites  are  willing
       to  relay files for other sites.  The UUCP network depends
       on direct distance dialing networks and off-peak long distance
 rates for its continued functioning.

   The UUCP Software    [Toc]    [Back]
       The  UUCP software contains the following components: System
 directories that  contain  UUCP  files  and  programs.
       Configuration  files  that  contain  information needed to
       establish remote connections and determine access  permissions.

              These files are used to describe the UUCP operating
              environment to  the  uucico  daemon.  Configuration
              files  specify,  for  example, remote system names,
              times of data transfer, valid  login  names,  passwords,
  and  the commands that can be executed on a
              system.  Administrative files that are used primarily
 in transferring data between computers

              Log  files  record  both successful and failed data
              transfers by the  administrative  files.  Logs  can
              occupy  much disk space unless you regularly delete
              some of them. The UUCP system  provides  facilities
              for pruning log files.

              Spool  or queue files contain the data and transfer
              requests that are issued from the uucp  and  uucico
              commands.   There are several types of spool files:
              Execution files are generated only by the uux  command.
  They  contain the commands to be executed on
              the remote system. By convention,  execution  files
              are named X.filename.  Command files are created by
              both the uucp and uux commands. They  contain  commands
  for transferring files to remote systems. By
              convention, command  files  are  named  C.filename.
              Data  files contain the data that is transferred to
              remote systems. They are created by  the  uucp  and
              uux  commands.  By convention, data files are named
              D.filename.  Public directories  that  contain  the
              files transferred by UUCP.  User commands that perform
 the basic UUCP functions, such as file  transfer
 and remote command execution.

              The  uucp  and  uux commands allow remote file copy
              and command execution, respectively. Both  commands
              allow users to specify remote system names in pathnames.

              The uucp and cp commands use similar syntax.   However,
  cp works immediately and copies files on the
              local system, while uucp operates in batch mode and
              allows  file  transfers  between  two systems. User
              requests are queued to  public  spool  files  where
              they wait for further processing by the uucico daemon
 (UNIX-to-UNIX copy-in, copy-out program).

              The uux command provides a  shell-like  environment
              for issuing commands on remote systems. As the user
              works, the uux command generates  an  execute  file
              that is sent to a spool directory to await transfer
              to a remote system.  Administrative commands,  such
              as  programs that enable you to configure and maintain
 UUCP.  Daemon programs that handle file transfers,
  communications  with  TCP/IP,  scheduling of
              work, and remote command executions.

              The uucico daemon, together with its  subprocesses,
              manages machine-to-machine communications. It works
              through control and log files, as well as a set  of
              public directories that contain the requests generated
 by the uucp and uux commands.

       The UUCP system can use any of several physical and transport
  layer  protocols.   The  uucico daemon supports both
       direct and remote connections through a serial  interface.
       Typically,  remote  connections use modems and direct distance
 dialing networks. The UUCP  system  uses  error-correcting
  modem  protocols  to ensure data integrity during

       The uucpd daemon supports UUCP over TCP/IP  networks.   It
       performs  login  and  password  authentication  before  it
       starts the uucico daemon. This configuration option allows
       you to take advantage of high-speed local area networks in
       order to do batched file transfers.  Note that TCP/IP does
       not replace UUCP protocols; it serves as a transport mechanism

       Because users on  remote  systems  can  log  in,  transfer
       files,  and execute commands, UUCP is a potential security
       problem for the local system. The UUCP system does provide
       a means to restrict what users can do on the local system,
       and likewise local UUCP users can be similarly  restricted
       by remote systems.

       Although many installations use UUCP to support electronic
       mail and news only, UUCP is not restricted to these  uses.
       For systems without LAN connections, UUCP can provide data
       transfer capabilities not otherwise available.

   The UUCP File and Directory Structure    [Toc]    [Back]
       The UUCP system uses  several  directories  and  files  to
       track   its   activities.   These  directories  and  files
       include:  Public  directories  with  unrestricted   access
       rights  Administrative directories and subfiles Configuration
 files Lock files

       Most UUCP directories and  files  are  included  when  the
       software is installed.  Some administrative files are created
 by various UUCP programs as they run.

       The UUCP public directory (/var/spool/uucppublic) contains
       files  transferred to the local system from other systems.
       The files remain in the public directory until users claim
       them  or  until  the commands requested by users on remote
       systems are executed by the uuxqt  daemon.  If  the  files
       were  sent to the UUCP public directory with the uuto command,
 the user must claim them with  the  uupick  command.
       Otherwise they can copy the files from that directory manually.
 The uucppublic directory, which contains  a  subdirectory
  for  each  remote  system that sends files to the
       local system, is created when UUCP is installed.

       The UUCP configuration files reside in  the  /usr/lib/uucp
       directory.  You  configure these files for systems at your
       site. You must  configure  the  following  files:  Systems
       Devices Permissions

       Configuring the other files is optional.

       The  configuration  files contain information about remote
       systems contacted by UUCP, the  devices  used  to  contact
       these  systems,  the times to contact the systems, and the
       level of access that remote systems can have to the  local
       system.  Some  configuration  files also specify limits on
       UUCP activities to prevent the local system from  becoming

       For  details  about UUCP configuration files, refer to the
       Network Administration: Services manual.

       Whenever UUCP connects to a remote computer,  it  makes  a
       lock  file  for  both  the  local and remote communication
       devices in the /var/spool/locks directory. Lock  files  on
       remote  devices prevent other instances of the uucico daemon
 from establishing duplicate connections  to  the  same
       remote  system.  When a local device contains a lock file,
       UUCP waits until the device becomes available, or it  uses
       another device for communications.

   The UUCP Daemons    [Toc]    [Back]
       Normally,  on  an  OSF/1 system, UUCP components reside in
       the /usr/adm, /usr/lbin, and /etc/uucp  directories.  However,
  on  the  Tru64  UNIX  system,  the UUCP daemons are
       stored in the  /usr/lib/uucp  directory,  except  for  the
       uucpd  daemon, which is stored in the /usr/sbin directory.
       The following table lists the daemons and their functions.

       Name      Function
       uucico    Manages file transfers
       uusched   Manages job scheduling
       uuxqt     Performs remote command execution
       uucpd     Enables UUCP connections through TCP/IP

       In  a typical configuration, the cron daemon automatically
       starts the uucico, uusched, and uuxqt  commands  according
       to a schedule set by the system administrator. For testing
       and debugging the UUCP configuration, the daemons also can
       be started by someone with superuser privileges.

       See cron(8) for more information.

   The uucico Daemon    [Toc]    [Back]
       The  uucico  daemon  transports the files required to send
       data from one UNIX system to another  UNIX  system.   Most
       UUCP  directories are created when UUCP is installed; however,
 the uucico daemon also creates some files during its
       operation. The uucico daemon performs the following tasks:
       Scans spool directories for jobs Contacts  remote  systems
       at  times  you  specify  Selects  data  transfer protocols
       Exchanges jobs with remote systems Logs jobs requested and

       When  the uucico daemon initiates contact with remote systems,
 it operates in master mode. In this mode, the uucico
       daemon  starts another slave process on the remote system.
       When  it  operates  in  master  mode,  the  uucico  daemon
       attempts  to  process  jobs queued on its local system; in
       slave mode the uucico daemon carries out requests made  by
       a  remote  uucico process.  Once the uucico daemon is finished
 processing its locally queued  jobs  on  the  remote
       system, the two processes can switch their roles as master
       and slave in order to exchange data in both directions.

       The uucp and uux commands each start the uucico daemon  to
       transfer  command,  data,  and execute files to the designated
 system. The uucico daemon is also  started  periodically
 by the uusched daemon, which handles the transfer of
       files queued in the local spooling directory.

       Once started by the  uusched  daemon,  the  uucico  daemon
       attempts to contact other systems and execute the instructions
 in the command files.   To  execute  those  instructions,
  the uucico daemon checks the /usr/lib/uucp/Systems
       file to find an entry for the system to be called.   Then,
       it  checks  the  Systems  file entry to see if the current
       time is a valid time to call. If so, it  checks  the  Type
       and  Class  fields  in  the Systems file, and searches the
       /usr/lib/uucp/Devices file to find a device  that  matches
       these fields.

       After  it  finds  a  device,  the uucico daemon checks the
       /var/spool/locks directory to ensure that  the  device  is
       not  locked  by another process.  If the device is locked,
       the daemon checks for another device of the requested type
       and speed, and uses it, if available.

       When  no  device  is  available, the daemon returns to the
       Systems file to find another entry for the remote  system.
       If one exists, the daemon repeats the process of searching
       for a device. If none is found,  the  daemon  records  the
       attempt   to   contact  the  remote  system  in  the  file
       /var/spool/uucp/.Status/SystemName and goes on to  process
       the  next  request. The command file remains in the queue,
       and the uucico daemon repeats the transfer attempt.

       When the uucico daemon reaches the remote system, it  logs
       in  using  the  information in the local Systems file pertaining
 to the remote system file. Logging  in  causes  an
       instance  of the uucico daemon to be invoked on the remote

       The two daemons, one on each system, work together to make
       the  transfer.   The  uucico  daemon on the calling system
       controls the link, specifying  the  requests  to  be  performed.
  The uucico daemon on the remote system checks the
       local permissions to see whether they allow the request to
       be performed.  If so, the file transfer starts.

       After  the  uucico  daemon  on the calling system finishes
       transferring all the requests it has for the  remote  system,
  it  sends  a hang-up request. When the remote uucico
       daemon has transactions to send to the calling system,  it
       denies  the  hang-up  request, and the two daemons reverse

       The /usr/lib/uucp/Permissions file on either the local  or
       the remote system can forbid the daemons to reverse roles.
       In such cases, the remote system  must  wait  to  transfer
       files  until  it  calls  the local system. When nothing is
       left to be transferred in either direction, the  two  daemons
  hang up. Throughout the transfer process, the uucico
       daemons on both systems write messages  in  UUCP  log  and
       error files.

   The uusched Daemon    [Toc]    [Back]
       The  uusched  daemon  schedules the transfer of files that
       are   queued   in    the    local    spooling    directory
       /var/spool/uucp.   When  the uusched daemon is invoked, it
       scans the spooling directory for command files, then  randomizes
  the  files  and  starts  the uucico daemon, which
       actually transfers the files.

   The uuxqt Daemon    [Toc]    [Back]
       The uuxqt daemon interprets execution files created  on  a
       remote  system  and transferred to the local system by the
       uucico daemon. Normally,  the  uucico  daemon  starts  the
       uuxqt  process to execute queued X* files.  The uuxqt daemon
 searches the spool  directory  for  command  execution
       requests. When it locates such a request, the uuxqt daemon
       checks for necessary files and permissions  and  then,  if
       permitted, executes the specified command.

   The uucpd Daemon    [Toc]    [Back]
       The  uucpd  daemon handles communications between UUCP and
       TCP/IP. This daemon enables users on systems linked over a
       local  area network to establish UUCP connections to other
       systems. Its job is to perform login authentication before
       transferring control to the uucico daemon, which completes
       the data transfer.  The uucpd daemon  is  started  by  the
       inetd  daemon,  after  configuring the /etc/inetd.conf and
       /etc/services files, and is not required to be running  on
       the local side.

       For details, refer to the Network Administration: Services

SEE ALSO    [Toc]    [Back]

       Commands: ct(1) ,cu , tip(1) ,uucico , uucleanup(8), uuencode(1),   uulog(1),   uuname(1),  uupick(1),  uusched(8),
       uusend(1), uustat(1), uuto(1), uux(1), uuxqt(1)

       Network Administration: Services

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