Postfix manual - proxymap(8)

    PROXYMAP(8)                                           PROXYMAP(8)

    NAME
           proxymap - Postfix lookup table proxy server

    SYNOPSIS
           proxymap [generic Postfix daemon options]

    DESCRIPTION
           The  proxymap  server provides read-only table lookup ser-
           vice to Postfix processes. The purpose of the service is:

           o      To overcome chroot  restrictions.  For  example,  a
                  chrooted  SMTP  server  needs  access to the system
                  passwd file in order to reject mail  for  non-exis-
                  tent  local  addresses,  but it is not practical to
                  maintain a copy of the passwd file  in  the  chroot
                  jail.  The solution:

                  local_recipient_maps =
                      proxy:unix:passwd.byname $alias_maps

           o      To  consolidate the number of open lookup tables by
                  sharing one open table  among  multiple  processes.
                  For  example,  making  mysql connections from every
                  Postfix daemon process results in "too many connec-
                  tions" errors. The solution:

                  virtual_alias_maps =
                      proxy:mysql:/etc/postfix/virtual_alias.cf

                  The  total  number of connections is limited by the
                  number of proxymap server processes.

           The proxymap server implements the following requests:

           open maptype:mapname flags
                  Open the table with type maptype and name  mapname,
                  as controlled by flags. The reply includes the map-
                  type dependent flags (to distinguish a fixed string
                  table from a regular expression table).

           lookup maptype:mapname flags key
                  Look  up  the  data stored under the requested key.
                  The reply is the  request  completion  status  code
                  (below)  and  the  lookup  result  value.  The map-
                  type:mapname and flags are the  same  as  with  the
                  open request.

           There  is  no  close  command,  nor  are tables implicitly
           closed when a client disconnects. The purpose is to  share
           tables among multiple client processes.

    SERVER PROCESS MANAGEMENT
           proxymap  servers  run under control by the Postfix master
           server.  Each server can handle multiple simultaneous con-
           nections.   When  all servers are busy while a client con-
           nects, the master creates a new proxymap  server  process,
           provided  that  the  process  limit is not exceeded.  Each
           server terminates after serving at least $max_use  clients
           or after $max_idle seconds of idle time.

    SECURITY
           The  proxymap  server  opens only tables that are approved
           via the proxy_read_maps configuration parameter, does  not
           talk  to  users,  and  can  run  at  fixed  low privilege,
           chrooted or not.  However,  running  the  proxymap  server
           chrooted  severely  limits  usability, because it can open
           only chrooted tables.

           The proxymap server is not a trusted daemon  process,  and
           must  not be used to look up sensitive information such as
           user or group IDs, mailbox file/directory names or  exter-
           nal commands.

    DIAGNOSTICS
           Problems and transactions are logged to syslogd(8).

    BUGS
           The  proxymap server provides service to multiple clients,
           and must therefore not be used for tables that have  high-
           latency lookups.

    CONFIGURATION PARAMETERS
           On  busy  mail  systems  a long time may pass before prox-
           ymap(8) relevant changes to main.cf are picked up. Use the
           command "postfix reload" to speed up a change.

           The  text  below  provides  only  a parameter summary. See
           postconf(5) for more details including examples.

           config_directory (see 'postconf -d' output)
                  The default location of  the  Postfix  main.cf  and
                  master.cf configuration files.

           daemon_timeout (18000s)
                  How  much time a Postfix daemon process may take to
                  handle a request  before  it  is  terminated  by  a
                  built-in watchdog timer.

           ipc_timeout (3600s)
                  The time limit for sending or receiving information
                  over an internal communication channel.

           max_idle (100s)
                  The maximum amount of time  that  an  idle  Postfix
                  daemon  process  waits for the next service request
                  before exiting.

           max_use (100)
                  The maximal number of connection requests before  a
                  Postfix daemon process terminates.

           process_id (read-only)
                  The  process ID of a Postfix command or daemon pro-
                  cess.

           process_name (read-only)
                  The process name of a  Postfix  command  or  daemon
                  process.

           proxy_read_maps (see 'postconf -d' output)
                  The  lookup  tables  that the proxymap(8) server is
                  allowed to access.

    LICENSE
           The Secure Mailer license must be  distributed  with  this
           software.

    HISTORY
           The proxymap service was introduced with Postfix 2.0.

    AUTHOR(S)
           Wietse Venema
           IBM T.J. Watson Research
           P.O. Box 704
           Yorktown Heights, NY 10598, USA

                                                          PROXYMAP(8)