Virtual Services Howto

Table of Contents

  1. Introduction

     1.1 Knowledge Required
     1.2 Purpose
     1.3 Feedback
     1.4 Revision History
     1.5 Copyright/Distribution

  2. IP Aliasing

  3. Virtuald

     3.1 Introduction
     3.2 Inetd
     3.3 Config File
     3.4 Source

  4. Shell Scripts

     4.1 Virtfs
     4.2 Virtexec
     4.3 Notes

  5. DNS

  6. Syslogd

     6.1 Problem
     6.2 Solution
        6.2.1 Setup Links
        6.2.2 Syslogd.init
     6.3 Multiple Syslogd's
        6.3.1 One Per Disk
        6.3.2 One Per Domain

  7. Virtual FTP

     7.1 Inetd
     7.2 Anonymous FTP
     7.3 Virtual FTP Users

  8. Virtual Web

     8.1 Running With Virtuald
        8.1.1 Not recommended
        8.1.2 Inetd
        8.1.3 Httpd.conf
        8.1.4 Configuration
        8.1.5 Httpd.init
     8.2 Running With Apache VirtualHost
        8.2.1 Access.conf
        8.2.2 Httpd.conf
        8.2.3 Srm.conf
        8.2.4 Httpd.init
     8.3 File Descriptor Overflow
        8.3.1 Warning
        8.3.2 Multiple Apache Servers
     8.4 Sharing Servers With One IP
        8.4.1 Saving IPs
        8.4.2 Drawback
     8.5 More Information

  9. Virtual Mail/Pop

     9.1 Problem
     9.2 Solution
     9.3 Sendmail Solution
        9.3.1 Introduction
        9.3.2 Create Sendmail Configuration File
        9.3.3 Edit Sendmail Configuration File
        9.3.4 Sendmail Local Delivery
        9.3.5 Sendmail Between Virtual Domains: The Hack (PRE8.8.6)
        9.3.6 Sendmail Between Virtual Domains: New Sendmail Feature (POST8.8.6)
        9.3.7 Sendmail.init
        9.3.8 Inetd Setup
     9.4 Qmail Solution
        9.4.1 Introduction
        9.4.2 Setup Virtual Domains
        9.4.3 Setup Domain Master User
        9.4.4 Tcpserver
        9.4.5 Qmail.init
        9.4.6 Source
        9.4.7 Source
     9.5 Acknowledgement

  10. Virtual Samba

     10.1 Setup
     10.2 Inetd
     10.3 Smb.init

  11. Virtual Other

  12. Conclusion

  13. FAQ


  1.  Introduction

  1.1.  Knowledge Required

  Creating a virtual services machine is not all that difficult,
  however, more than fundamental knowledge is required.  This document
  is not a primer to how to fully configure a Linux machine.

  In order to understand this HOWTO document it is assumed that you are
  thoroughly familiar with the following:

  o  Compiling a Linux kernel and adding IP aliasing support IP alias

  o  Setting up and configuring of network devices NET-3 HOWTO

  o  Setting up of inetd NET-3 HOWTO

  o  Various network packages like Sendmail Apache Qmail SAMBA

  o  Setting up DNS DNS HOWTO

  o  Understanding basic system administration Linux Systems
     Administrators's Guide

  o  Understanding how to setup a Web Server WWW HOWTO

  If you are uncertain of how to proceed with any of the above it is
  STRONGLY recommended that you use the html links provided to
  familiarize yourself with all packages.  I will NOT reply to mail
  regarding any of the above.  Please direct your questions to the
  appropriate author of the HOWTO.

  1.2.  Purpose

  The purpose of virtual services is to allow a single machine to
  recognize multiple IP addresses without multiple network cards.  IP
  aliasing is a kernel option that allows you to assign each network
  device more than one IP address.  The kernel then multiplexes (swaps
  between them very fast) in the background and to the user it appears
  like you have more than one server.

  This multiplexing allows multiple domains (,, etc.) to be hosted by the same machine for the same
  cost as hosting one domain.  Unfortunately, most services (FTP, web,
  mail) were not designed to handle muliple domains.  In order to make
  them work properly you must modify both configuration files and source
  code.  This document describes how to make these modifications in the
  setting up of a virtual machine.

  A deamon is also required in order to make virtual services function.
  The source for this daemon (virtuald) is provided later in this

  1.3.  Feedback

  This document will expand as packages are updated and source or
  configuration modifications change.   If there are any portions of
  this document that are unclear please feel free to email me with your
  suggestions or questions.  So that I do not have to go searching
  through the entire HOWTO please make certain that all comments are as
  specific as possible and include the section where the uncertainty
  lies.  It is important that all mail be addressed with VIRTSERVICES
  HOWTO in the subject line.  Any other mail will be considered personal
  and all my friends know that I do not ever read my personal mail so it
  will probably get discarded with theirs.

  Please note that my examples are just that, examples and should not be
  copied verbatim.   You may have to insert your own values.   If you
  are having trouble, send me mail.  Include all the pertinent
  configuration files and the error messages you get when installing and
  I will look them over and reply with my suggestions.

  1.4.  Revision History


  Initial version


  Fixed error in Virtual Web Section


  Fixed the date


  Updated html links.

  Web updates.

  New Sendmail option.

  New Qmail section.

  Syslogd updates.

  FTP updates.

  Virtuald default option.

  New SAMBA section.

  FAQ updates.


  Changed all paths to /usr/local.

  Added virtuald VERBOSELOG compile option.

  Fixed setuid/setgid bug in virtmailfilter.

  Fixed execl bug in virtmailfilter.

  Fixed capitialization bug in virtmailfilter.

  Fixed environment variable sanity check in virtmailfilter.

  Removed mbox code from virtmailfilter/virtmaildelivery.

  Added tcpserver.init pop section for Qmail.

  Added alias domain name question to the FAQ.

  Fixed virtmailfilter to send home directory to virtmaildelivery.

  1.5.  Copyright/Distribution

  This document is Copyright (c) 1997 by The Computer Resource Center

  A verbatim copy may be reproduced or distributed in any medium
  physical or electronic without permission of the author.  Translations
  are similiarly permitted without express permission if it includes a
  notice on who translated it.  Commercial redistribution is allowed and
  encouraged; however please notify Computer Resource Center of any such

  Excerpts from the document may be used without prior consent provided
  that the derivative work contains the verbatim copy or a pointer to a
  verbatim copy.

  Permission is granted to make and distribute verbatim copies of this
  document provided the copyright notice and this permission notice are
  preserved on all copies.

  In short, we wish to promote dissemination of this information through
  as many channels as possible. However, I do wish to retain copyright
  on this HOWTO document, and would like to be notified of any plans to
  redistribute this HOWTO.

  2.  IP Aliasing

  IP aliasing is a kernel option that needs to be set up in order to run
  a virtual hosting machine.  There is already a mini-HOWTO on IP
  aliasing.  Consult that for any questions on how to set it up.

  3.  Virtuald

  3.1.  Introduction

  Every network connection is made up of two IP address/port pairs.  The
  API (Applications Program Interface) for network programming is called
  the Sockets API.  The socket acts like an open file and by
  reading/writing to it you can send data over a network connection.
  There is a function call  getsockname  that will return the IP address
  of the local socket.  Virtuald uses  getsockname to determine which IP
  on the local machine is being accessed.  Virtuald reads a config file
  to retrieve the directory associated with that IP.  It will
   chroot  to that directory and hand the connection off to the service.
  Chroot  resets / or the root directory to a new point so everything
  higher in the directory tree is cut off from the running program.
  Therefore, each IP address gets their own virtual filesystem.   To the
  network program this is transparent and the program will behave like
  nothing happened.  Virtuald in conjunction with a program like inetd
  can then be used to virtualize any service.

  3.2.  Inetd

  Inetd is a network super server that listens at multiple ports and
  when it receives a connection (for example, an incoming pop request),
  inetd performs the network negotiation and hands the network
  connection off to the specified program.  This prevents services from
  running idly when they are not needed.

  A standard /etc/inetd.conf file looks like this:

  ftp stream tcp nowait root /usr/sbin/tcpd \
          wu.ftpd -l -a
  pop-3 stream tcp nowait root /usr/sbin/tcpd \
          in.qpop -s

  A virtual /etc/inetd.conf file looks like this:

  ftp stream tcp nowait root /usr/local/bin/virtuald \
          virtuald /virtual/conf.ftp wu.ftpd -l -a
  pop-3 stream tcp nowait root /usr/local/bin/virtuald \
          virtuald /virtual/conf.pop in.qpop -s

  3.3.  Config File

  Each service gets a config file that will control what IPs and
  directories are allowed for that service.  You can have one master
  config file or several config files if you want each service to get a
  different list of domains.   A config file looks like this:

  # This is a comment and so are blank lines

  # Format IP SPACE dir NOSPACES /virtual/ /virtual/ /virtual/

  # Default option for all other IPs
  default /

  3.4.  Source

  This is the C source code to the virtuald program.  Compile it and
  install it in /usr/local/bin with permission 0755, user root, and
  group root.  The only compile option is VERBOSELOG which will turn
  on/off logging of connections.

  #include <netinet/in.h>
  #include <sys/socket.h>
  #include <arpa/inet.h>
  #include <stdarg.h>
  #include <unistd.h>
  #include <string.h>
  #include <syslog.h>
  #include <stdio.h>


  #define BUFSIZE 8192

  int getipaddr(char **ipaddr)
          struct sockaddr_in virtual_addr;
          static char ipaddrbuf[BUFSIZE];
          int virtual_len;
          char *ipptr;

          if (getsockname(0,(struct sockaddr *)&virtual_addr,&virtual_len)<0)
                  syslog(LOG_ERR,"getipaddr: getsockname failed: %m");
                  return -1;
          if (!(ipptr=inet_ntoa(virtual_addr.sin_addr)))
                  syslog(LOG_ERR,"getipaddr: inet_ntoa failed: %m");
                  return -1;
          return 0;

  int iptodir(char **dir,char *ipaddr,char *filename)
          char buffer[BUFSIZE],*bufptr;
          static char dirbuf[BUFSIZE];
          FILE *fp;

          if (!(fp=fopen(filename,"r")))
                  syslog(LOG_ERR,"iptodir: fopen failed: %m");
                  return -1;
                  if (*buffer=='#' || *buffer==0)
                  if (!(bufptr=strchr(buffer,' ')))
                          syslog(LOG_ERR,"iptodir: strchr failed");
                          return -1;
                  if (!strcmp(buffer,ipaddr))
                  if (!strcmp(buffer,"default"))
          if (fclose(fp)==EOF)
                  syslog(LOG_ERR,"iptodir: fclose failed: %m");
                  return -1;
          if (!*dir)
                  syslog(LOG_ERR,"iptodir: ip not found in conf file");
                  return -1;
          return 0;

  int main(int argc,char **argv)
          char *ipaddr,*dir;


          syslog(LOG_ERR,"Virtuald Starting: $Revision: 1.49 $");
          if (!argv[1])
                  syslog(LOG_ERR,"invalid arguments: no conf file");
          if (!argv[2])
                  syslog(LOG_ERR,"invalid arguments: no program to run");
          if (getipaddr(&ipaddr))
                  syslog(LOG_ERR,"getipaddr failed");
          syslog(LOG_ERR,"Incoming ip: %s",ipaddr);
          if (iptodir(&dir,ipaddr,argv[1]))
                  syslog(LOG_ERR,"iptodir failed");
          if (chroot(dir)<0)
                  syslog(LOG_ERR,"chroot failed: %m");
          syslog(LOG_ERR,"Chroot dir: %s",dir);
          if (chdir("/")<0)
                  syslog(LOG_ERR,"chdir failed: %m");
          if (execvp(argv[2],argv+2)<0)
                  syslog(LOG_ERR,"execvp failed: %m");



  4.  Shell Scripts

  4.1.  Virtfs

  Each domain should get their own directory structure.  Since you are
  using  chroot  you will require duplicate copies of the shared
  libraries, binaries, conf files, etc.  I use /virtual/ for
  each domain that I create.

  I realize that you are taking up more disk space but it is cheaper
  than a whole new machine and network cards.  If you really want to
  preserve space you can hard link the files together so only one copy
  of each binary exists.  The filesystem that I use takes up a little
  over 2M.  However, this script attempts to copy all the files from the
  main filesystem in order to be as generic as possible.

  Here is a sample virtfs script:


  echo '$Revision: 1.49 $'

  echo -n "Enter the domain name: "
  read domain

  if [ "$domain" = "" ]
          echo Nothing entered: aborting
          exit 0


  echo -n "Enter leading dir: (Enter for default: $leadingdir): "
  read ans

  if [ "$ans" != "" ]


  if [ -d "$newdir" ]
          echo New directory: $newdir: ALREADY exists
          exit 0
          echo New directory: $newdir

  echo Create $newdir
  mkdir -p $newdir

  echo Create bin
  cp -pdR /bin $newdir

  echo Create dev
  cp -pdR /dev $newdir

  echo Create dev/log
  ln -f /virtual/log $newdir/dev/log

  echo Create etc
  mkdir -p $newdir/etc
  for i in /etc/*
          if [ -d "$i" ]
          cp -pd $i $newdir/etc

  echo Create etc/skel
  mkdir -p $newdir/etc/skel

  echo Create home
  for i in a b c d e f g h i j k l m n o p q r s t u v w x y z
          mkdir -p $newdir/home/$i

  echo Create home/c/crc
  mkdir -p $newdir/home/c/crc
  chown crc.users $newdir/home/c/crc

  echo Create lib
  mkdir -p $newdir/lib
  for i in /lib/*
          if [ -d "$i" ]
          cp -pd $i $newdir/lib

  echo Create proc
  mkdir -p $newdir/proc

  echo Create sbin
  cp -pdR /sbin $newdir

  echo Create tmp
  mkdir -p -m 0777 $newdir/tmp
  chmod +t $newdir/tmp

  echo Create usr
  mkdir -p $newdir/usr

  echo Create usr/bin
  cp -pdR /usr/bin $newdir/usr

  echo Create usr/lib
  mkdir -p $newdir/usr/lib

  echo Create usr/lib/locale
  cp -pdR /usr/lib/locale $newdir/usr/lib

  echo Create usr/lib/terminfo
  cp -pdR /usr/lib/terminfo $newdir/usr/lib

  echo Create usr/lib/zoneinfo
  cp -pdR /usr/lib/zoneinfo $newdir/usr/lib

  echo Create usr/lib/\*.so\*
  cp -pdR /usr/lib/*.so* $newdir/usr/lib

  echo Create usr/sbin
  cp -pdR /usr/sbin $newdir/usr

  echo Linking usr/tmp
  ln -s /tmp $newdir/usr/tmp

  echo Create var
  mkdir -p $newdir/var

  echo Create var/lock
  cp -pdR /var/lock $newdir/var

  echo Create var/log
  mkdir -p $newdir/var/log

  echo Create var/log/wtmp
  cp /dev/null $newdir/var/log/wtmp

  echo Create var/run
  cp -pdR /var/run $newdir/var

  echo Create var/run/utmp
  cp /dev/null $newdir/var/run/utmp

  echo Create var/spool
  cp -pdR /var/spool $newdir/var

  echo Linking var/tmp
  ln -s /tmp $newdir/var/tmp

  echo Create var/www/html
  mkdir -p $newdir/var/www/html
  chown webmast.www $newdir/var/www/html
  chmod g+s $newdir/var/www/html

  echo Create var/www/master
  mkdir -p $newdir/var/www/master
  chown webmast.www $newdir/var/www/master

  echo Create var/www/server
  mkdir -p $newdir/var/www/server
  chown webmast.www $newdir/var/www/server

  exit 0

  4.2.  Virtexec

  To execute commands in a virtual environment you have to
   chroot  to that directory and then run the command.  I have written a
  special shell script called virtexec that handles this for any


  echo '$Revision: 1.49 $'

  BNAME=`basename $0`
  FIRST4CHAR=`echo $BNAME | cut -c1-4`
  REALBNAME=`echo $BNAME | cut -c5-`

  if [ "$BNAME" = "virtexec" ]
          echo Cannot run virtexec directly: NEED a symlink
          exit 0

  if [ "$FIRST4CHAR" != "virt" ]
          echo Symlink not a virt function
          exit 0

  for i in /virtual/*
          if [ ! -d "$i" ]
          if [ "$i" = "/virtual/lost+found" ]
          list="$list $i $num"
          num=`expr $num + 1`

  if [ "$list" = "" ]
          echo No virtual environments exist
          exit 0

  dialog --clear --title 'Virtexec' --menu Pick 20 70 12 $list 2> /tmp/menu.$$
  if [ "$?" = "0" ]
          newdir=`cat /tmp/menu.$$`
  tput clear
  rm -f /tmp/menu.$$

  echo '$Revision: 1.49 $'

  if [ ! -d "$newdir" ]
          echo New directory: $newdir: NOT EXIST
          exit 0
          echo New directory: $newdir

  echo bname: $BNAME

  echo realbname: $REALBNAME

  if [ "$*" = "" ]
          echo args: none
          echo args: $*

  echo Changing to $newdir
  cd $newdir

  echo Running program $REALBNAME

  chroot $newdir $REALBNAME $*

  exit 0

  Please note that you must have the  dialog  program installed on your
  system for this to work.  To use virtexec just symlink a program to
  it.  For example,

  ln -s /usr/local/bin/virtexec /usr/local/bin/virtpasswd
  ln -s /usr/local/bin/virtexec /usr/local/bin/virtvi
  ln -s /usr/local/bin/virtexec /usr/local/bin/virtpico
  ln -s /usr/local/bin/virtexec /usr/local/bin/virtemacs
  ln -s /usr/local/bin/virtexec /usr/local/bin/virtmailq

  Then if you type virtvi or virtpasswd or virtmailq it will allow you
  to vi a program, change a user's password or check the mail queue on
  your virtual system.  You can create as many virtexec symlinks as you
  want.  Please note that if your program requires a shared library it
  has to be in the virtual filesystem as well as the binary.

  4.3.  Notes

  I install all the scripts in /usr/local/bin.  Anything that I do not
  want to put on the virtual filesystem I put in /usr/local.  The script
  does not copy any of the files in /usr/local to the virtual
  filesystem.  Any files that are important to not cross virtual
  filesystems should be removed.  For example, ssh is installed on my
  system and I did not want the private key for the server available on
  all the virtual filesystems so I remove it from each virtual
  filesystem after I run virtfs.  I also change resolv.conf and remove
  anything that has the name of another domain on it for legal reasons.
  For example, /etc/hosts and /etc/HOSTNAME.

  The programs that I symlink to virtexec are:

  o  virtpasswd -- change a user password

  o  virtadduser -- create a user

  o  virtdeluser -- delete a user

  o  virtsmbstatus -- see SAMBA status

  o  virtvi -- edit a file

  o  virtmailq -- check out the mailq

  o  virtnewaliases -- rebuild alias tables

  5.  DNS

  You can configure DNS normally.  There is a HOWTO on DNS.

  6.  Syslogd

  6.1.  Problem

  Syslogd is the system logging utility commonly used on UNIX systems.
  Syslogd is a daemon that opens a special file called a FIFO.  A FIFO
  is a special file that acts like a pipe.  Anything that is written to
  the write side will come out the read side.  Syslogd waits for data
  from the read side.  There are C functions that write to the write
  side.  If your program uses these C functions your output will go to

  Remember that we have used a  chroot  environment and the FIFO that
  syslogd is reading from (/dev/log) is not present.  That means all the
  virtual environments will not log to syslogd.

  6.2.  Solution

  6.2.1.  Setup Links

  Syslogd can look to a different FIFO if you tell it on the command
  line so run syslogd with the argument:

  syslogd -p /virtual/log

  Then symlink /dev/log to /virtual/log by:

  ln -sf /virtual/log /dev/log

  Then hard link all the /dev/log copies to this file by running:

  ln -f /virtual/log /virtual/

  The virtfs script above already does this.  Since /virtual is one
  contiguous disk and the /dev/log's are hard linked they have the same
  inode number and point to the same data.  The  chroot  cannot stop
  this so all your virtual /dev/log's will now function.  Note that all
  the messages from all the environments will be logged in one place.
  However, you can write separate programs to filter out the data.

  6.2.2.  Syslogd.init

  This version of the syslogd.init file hard links the /dev/log's each
  time you start it because syslogd deletes and creates the /dev/log
  FIFO each time it runs.  Here is a modified syslogd.init file:


  . /etc/rc.d/init.d/functions

  case "$1" in
          echo -n "Starting dev log: "
          ln -sf /virtual/log /dev/log
          echo done
          echo -n "Starting system loggers: "
          daemon syslogd -p /virtual/log
          daemon klogd
          echo -n "Starting virtual dev log: "
          for i in /virtual/*
                  if [ ! -d "$i" ]
                  if [ "$i" = "/virtual/lost+found" ]
                  ln -f /virtual/log $i/dev/log
                  echo -n "."
          echo " done"
          touch /var/lock/subsys/syslogd
          echo -n "Shutting down system loggers: "
          killproc syslogd
          killproc klogd
          rm -f /var/lock/subsys/syslogd
          echo "Usage: syslogd {start|stop}"
          exit 1

  exit 0

  6.3.  Multiple Syslogd's

  6.3.1.  One Per Disk

  If you run out of space on one filesystem and you have to break up
  your virtual domains onto different disks remember that hard links
  will not cross disks.  That means you will have to run a separate
  syslogd for each group of domains on a disk.  For example, if you had
  thirteen domains on /virtual1 and fifteen domains on /virtual2, you
  would hard link thirteen domains to /virtual1/log and run one syslogd
  with  syslogd -p /virtual1/log  and hard link fifteen other domains to
  /virtual2/log with a syslogd running with  syslogd -p /virtual2/log .
  6.3.2.  One Per Domain

  If you do not want to centralize the logs to one place you could also
  run one syslogd per domain.  This wastes process ID's so I do not
  recommend it but it is easier to implement.   You would have to alter
  your syslogd.init file to run syslogd as  chroot /virtual/
  syslogd  for each domain.  This will run each syslogd within the
  chroot  and the logs will be in /virtual/ rather
  than all combined in /var/log.  Do not forget to run a syslogd
  normally  syslogd  for the main system and a kernel logger  klogd .

  7.  Virtual FTP

  7.1.  Inetd

  Wu-ftpd comes with built in support to make it virtual.  However, you
  cannot maintain separate password files for each domain.  For example,
  if  and  both want an account you would
  have to make one of them bob2 or have one of the users choose a
  different user name.  Since you now have a virtual filesystem for each
  domain you have separate password files and this problem goes away.
  Just create a virtnewuser script and a virtpasswd script in the way
  mentioned above and you are all set.

  The inetd.conf entries for wu-ftpd:

  ftp stream tcp nowait root /usr/local/bin/virtuald \
          virtuald /virtual/conf.ftp wu.ftpd -l -a

  7.2.  Anonymous FTP

  These are unaffected by the virtuald setup.  For an anonymous user
  just create the FTP user in /virtual/ like you
  would normally.

  ftp:x:14:50:Anonymous FTP:/var/ftp:/bin/false

  Then setup the anonymous FTP directory.  You have separate password
  files for each domain so you can restrict which domain has an
  anonymous FTP account.  Please note that since the FTP server is
  already  chrooted into the /virtual/ directory you do not
  have to prefix any paths with it.

  7.3.  Virtual FTP Users

  Wu-ftpd supports something called a guest group.  This allows you to
  create different FTP areas for each user.  The FTP server does a
  chroot  to the specified area so the user cannot go outside that
  directory tree.  If you create the users within a virtual domain this
  way they will not be able to view the system files.

  Add the guest's group to the /virtual/ file.

  Create an entry in /virtual/ with the  chroot
  dir and the starting home directory separated by  /./ :

  guest1:x:8500:51:Guest FTP:/home/g/guest1/./incoming:/bin/false

  Then setup guest's home like you would for anonymous FTP.  You have
  separate password files for each domain so you can specifiy which
  domains have guest accounts and which users within a domain are guest
  users.  Please note that since the FTP server is already  chrooted
  into the /virtual/ directory you do not have to prefix any
  paths with it.

  8.  Virtual Web

  8.1.  Running With Virtuald

  8.1.1.  Not recommended

  Apache has their own support for virtual domains.  This is the only
  program I recommend using the internal virtual domain mechanism.
  When you run something through inetd there is a cost, the program has
  to start up each time you run it.  This results in slower response
  time, which is perfectly fine for most services but is completely
  unacceptable for web service.  Apache also has a mechanism for
  stopping connections when too many come in, which can be critical for
  even medium volume sites.

  Simply stated, virtualizing Apache with virtuald is a really bad idea.
  The whole point of virtuald is to fill the gap created when services
  DO NOT have their own internal mechanism to do the job.  Virtuald is
  not meant to replace good code that already completes the task at

  The above not withstanding here is how to do it for those who are
  foolhardy enough to do so.

  8.1.2.  Inetd

  Edit /etc/inetd.conf

  vi /etc/inetd.conf # Add this line
  www stream tcp nowait www /usr/local/bin/virtuald \
          virtuald /virtual/conf.www httpd -f /var/www/conf/httpd.conf

  8.1.3.  Httpd.conf

  Edit /var/www/conf/httpd.conf

  vi /var/www/conf/httpd.conf # Or wherever you put the Apache config files
  It should say:
  ServerType standalone

  Replace it with:
  ServerType inetd

  8.1.4.  Configuration

  Then configure each instance of the Apache server like you would
  normally for single domain use.

  8.1.5.  Httpd.init

  An httpd.init file is not needed since the server is run through

  8.2.  Running With Apache VirtualHost

  Apache has three configuration files  access.conf ,  httpd.conf , and
  srm.conf .  Newer versions of Apache have made the three configuration
  files unnecessary.  However, I find that breaking up the configuration
  into three sections makes it easier to manage so I will be keeping
  with that style in this HOWTO document.

  8.2.1.  Access.conf

  This configuration file is used to control the accessibility of
  directories in the web directory structure.  Here is a sample
  configuration file that shows how to have different options for each

  # /var/www/conf/access.conf: Global access configuration

  # Options are inherited from the parent directory
  # Set the main directory with default options
  <Directory />
  AllowOverride None
  Options Indexes

  # Give one domain a passwd protected directory
  <Directory /virtual/>
  AuthUserFile /var/www/passwd/
  AuthGroupFile /var/www/passwd/
  AuthType Basic
  <Limit GET PUT POST>
  require valid-user

  # Give another domain Server Side Includes
  <Directory /virtual/>
  Options IncludesNOEXEC

  8.2.2.  Httpd.conf

  This configuration file is used to control the main options for the
  Apache server.  Here is a sample configuration file that shows how to
  have different options for each domain.

  # /var/www/conf/httpd.conf: Main server configuration file

  # Begin: main conf section

  # Needed since not using inetd
  ServerType standalone

  # Port to run on
  Port 80

  # Log clients with names vs IP addresses
  HostnameLookups on

  # User to run server as
  User www
  Group www

  # Where server config, error and log files are
  ServerRoot /var/www

  # Process Id of server in this file
  PidFile /var/run/

  # Internal server process info
  ScoreBoardFile /var/www/logs/apache_status

  # Timeout and KeepAlive options
  Timeout 400
  KeepAlive 5
  KeepAliveTimeout 15

  # Number of servers to run
  MinSpareServers 5
  MaxSpareServers 10
  StartServers 5
  MaxClients 150
  MaxRequestsPerChild 30

  # End: main conf section

  # Begin: virtual host section

  # Tell server to accept requests for ip:port
  # I have one for each IP needed so you can explicitly ignore certain domains

  # VirtualHost directive allows you to specify another virtual
  # domain on your server.  Most Apache options can be specified
  # within this section.

  # Mail to this address on errors

  # Where documents are kept in the virtual domain
  DocumentRoot /virtual/

  # Name of the server

  # Log files Relative to ServerRoot option
  ErrorLog logs/
  TransferLog logs/
  RefererLog logs/
  AgentLog logs/
  # Use CGI scripts in this domain
  ScriptAlias /cgi-bin/ /var/www/cgi-bin/
  AddHandler cgi-script .cgi
  AddHandler cgi-script .pl


  # Mail to this address on errors

  # Where documents are kept in the virtual domain
  DocumentRoot /virtual/

  # Name of the server

  # Log files Relative to ServerRoot option
  ErrorLog logs/
  TransferLog logs/
  RefererLog logs/
  AgentLog logs/

  # No CGI's for this host
  # End: virtual host section

  8.2.3.  Srm.conf

  This configuration file is used to control how requests are serviced
  and how results are formatted.   You do not have to edit anything here
  for the virtual domains.  The sample config file from Apache should

  8.2.4.  Httpd.init

  Nothing special has to be done to the httpd.init file.  Use a standard
  one that comes with the Apache configuration.

  8.3.  File Descriptor Overflow

  8.3.1.  Warning

  This only applies to the standalone style Apache server.  A server run
  through inetd does not interact with the other domains so it has the
  whole file descriptor table.

  Every log file that the Apache server opens is another file descriptor
  for the process.  There is a limit of 256 file descriptors per process
  in Linux.  Since you have multiple domains you are using a lot more
  file descriptors.  If you have too many domains running off of one
  Apache web server process you can overflow this table.  This would
  mean that certain logs would not work and CGI's would fail.

  8.3.2.  Multiple Apache Servers

  If you assume five file descriptors per domain you can have 50 domains
  running on your Apache server without any problems.  However, if you
  find your server having problems like this you could create /var/www1
  with an Apache server in charge of domain1 - domain25 and /var/www2
  with an Apache server in charge of domain26 - domain50 and so on.
  This would give each server their own configuration, error, and log
  directory.  Each server should be configured separately with their own
  Listen and VirtualHost directives.  Do not forget to run multiple
  servers in your httpd.init file.

  8.4.  Sharing Servers With One IP

  8.4.1.  Saving IPs

  The HTTP (HyperText Transfer Protocol) version 1.1 added a feature
  that communicates the name of the server to the client.  This means
  that the client does not need to look up the server from its IP
  address.  Therefore, two virtual servers could have the same IP
  address and be different web sites. The Apache configuration is the
  same as above except that you do not have to put in a different Listen
  directive since the two domains will have the same IP.

  8.4.2.  Drawback

  The only problem is that virtuald uses IP addresses to distinguish
  between domains.  In its current form virtuald would not be able to
  chroot to different spool directories for each domain.  Therefore,
  mail would only be able to respond as one IP and there would no longer
  be a unique spool directory for each domain.  All the web sharing IP
  clients would have to share that IPs spool directory.  That would mean
  duplicate usernames would be an issue again.  However, that is the
  price you pay for sharing IPs.

  8.5.  More Information

  This HOWTO only shows how to implement virtual support on the Apache
  web server.  Most web servers use a similar interface.  For more
  information on virtual web hosting consult the WWW HOWTO, the
  documentation for Apache at Apache's Site, or the documentation at

  9.  Virtual Mail/Pop

  9.1.  Problem

  Virtual mail support is in ever increasing demand.  Sendmail says it
  supports virtual mail.  What it does support is listening for incoming
  mail from different domains.  You can then specify to have the mail
  forwarded somewhere.  However, if you forward it to the local machine
  and have incoming mail to and they
  will go to the same mail folder.  This is a problem since both bob's
  are different people with different mail.

  9.2.  Solution

  You can make sure that each user name is unique by using a numbering
  scheme: bob1, bob2, etc or prepending a few characters to each
  username dom1bob, dom2bob, etc.  You could also hack mail and pop to
  do these conversions behind the scenes but that can get messy.
  Outgoing mail also has the banner and you want each
  subdomain's outgoing mail banner to be different.

  I have two solutions.  One works with sendmail and one works with
  Qmail.  The solution with sendmail should work with a stock install of
  sendmail.  However, it shares all the limitations built into sendmail.
  It also requires that one sendmail has to be run in queue mode for
  each domain.  Having 50 or more sendmail queue processes that wake up
  every hour can put a little strain on a machine.

  The solution offered with Qmail does not require multiple instances of
  Qmail and can run out of one queue directory.  It does require an
  extra program since Qmail does not rely on virtuald.  I believe a
  similar procedure can be done with sendmail.  However, Qmail lends
  itself to this solution more readily.

  I do not endorse any one program over the other.  The sendmail install
  is a little more straight forward but Qmail is probably the more
  powerful of the two mail server packages.

  9.3.  Sendmail Solution

  9.3.1.  Introduction

  Each virtual filesystem gives a domain its own /etc/passwd.  This
  means that and are different users in
  different /etc/passwds so mail will be no problem.  They also have
  their own spool directories so the mail folders will be different
  files on different virtual filesystems.

  9.3.2.  Create Sendmail Configuration File

  Create /etc/ like you would normally through m4.  I used:


  9.3.3.  Edit Sendmail Configuration File

  Edit /virtual/ to respond as your virtual

  vi /virtual/ # Approximately Line 86
  It should say:


  Replace it with:

  9.3.4.  Sendmail Local Delivery

  Edit /virtual/ with the local hostnames.

  vi /virtual/

  9.3.5.  Sendmail Between Virtual Domains: The Hack (PRE8.8.6)

  However, sendmail requires one minor source code modification.
  Sendmail has a file called /etc/ and it contains all
  machine names that sendmail will deliver mail to locally rather than
  forwarding to another machine.  Sendmail does internal checking of all
  the devices on the machine to initialize this list with the local IPs.
  This presents a problem if you are mailing between virtual domains on
  the same machine.  Sendmail will be fooled into thinking another
  virtual domain is a local address and spool the mail locally.  For
  example, sends mail to  Since's sendmail thinks is local, it will spool the
  mail on and never send it to  You have to
  modify sendmail (I did this on v8.8.5 without a problem):

  vi v8.8.5/src/main.c # Approximately Line 494
  It should say:


  Replace it with:

  /* load_if_names(); Commented out since hurts virtual */

  Note only do this if you need to send mail between virtual domains
  which I think is probable.

  This will fix the problem.  However, the main ethernet device eth0 is
  not removed.  Therefore, if you send mail from a virtual IP to the one
  on eth0 on the same box it will delivery locally.  Therefore, I just
  use this as a dummy IP (  I
  never send mail to this host so neither will the virtual domains.
  This is also the IP I would use to ssh into the box to check if the
  system is ok.

  9.3.6.  Sendmail Between Virtual Domains: New Sendmail Feature

  As of Sendmail V8.8.6, there is a new option to disable loading of the
  extra network interfaces.  This means you do NOT have to alter the
  code in any way.  It is called  DontProbeInterfaces .

  Edit /virtual/

  vi /virtual/ # Add the line
  O DontProbeInterfaces=True

  9.3.7.  Sendmail.init

  Sendmail cannot be started stand alone anymore so you have to run it
  through inetd.  This is inefficient and will result in lower start up
  time but if you had such a high hit site you would not share it on a
  virtual box with other domains.  Note that you are NOT running with
  the  -bd  flag.  Also note that you need a  sendmail -q  running for
  each domain to queue up undelivered mail. The new sendmail.init file:


  . /etc/rc.d/init.d/functions

  case "$1" in
          echo -n "Starting sendmail: "
          daemon sendmail -q1h
          echo -n "Starting virtual sendmail: "
          for i in /virtual/*
                  if [ ! -d "$i" ]
                  if [ "$i" = "/virtual/lost+found" ]
                  chroot $i sendmail -q1h
                  echo -n "."
          echo " done"
          touch /var/lock/subsys/sendmail
          echo -n "Stopping sendmail: "
          killproc sendmail
          rm -f /var/lock/subsys/sendmail
          echo "Usage: sendmail {start|stop}"
          exit 1

  exit 0

  9.3.8.  Inetd Setup

  Pop should install normally with no extra effort.  It will just need
  the inetd entry for it with the virtuald part added.  The inetd.conf
  entries for sendmail and pop:

  pop-3 stream tcp nowait root /usr/local/bin/virtuald \
          virtuald /virtual/conf.pop in.qpop -s
  smtp stream tcp nowait root /usr/local/bin/virtuald \
          virtuald /virtual/conf.mail sendmail -bs

  9.4.  Qmail Solution

  9.4.1.  Introduction

  This solution takes over the delivery responsibilities of qmail-local,
  so use of the .qmail files in the virtual home directories will not
  work.  However, each domain will still get a domain master user that
  will control aliasing for the whole domain.  Two external programs
  will be used for that domain masters .qmail-default file.  The mail
  will be passed through these two programs in order to deliver mail for
  each domain.

  Two programs are required since one of them is run setuid root.  It is
  a small program that changes to a non-root user and then runs the
  second program.  Consult your nearest security related site for a
  discussion as to why this is necessary.

  This solution bypasses the need for using virtuald.  Qmail is flexible
  enough to not require a general virtuald setup.  Qmail's design
  utilizes the chaining of programs together to deliver mail.  This
  design makes it very easy to insert the virtual section into the Qmail
  delivery process without altering a stock install of Qmail.

  A note that since you are using one Qmail any unqualified domain name
  will be expanded with the domain of the main server.  This is because
  you do not have a separate Qmail server for each domain.  Therefore,
  make sure that your client (Eudora, elm, mutt, etc.) knows to expand
  all of your unqualified domain names.

  9.4.2.  Setup Virtual Domains

  Qmail has to be configured to accept mail for each of the virtual
  domains you will be serving.  Type the following commands.

  echo "" >> /var/qmail/control/virtualdomains

  9.4.3.  Setup Domain Master User

  Add to your main /etc/passwd file the user domain1.  I would make the
  shell /bin/false so that the domain master cannot log in.   That user
  will be able to add .qmail files and all mail for domain1 will route
  through that account.  Note that usernames can only be eight
  characters long and domain names can be longer.  The remaining
  characters are truncated.  That means that user domain12 and domain123
  are going to be the same user and Qmail might get confused.  So be
  careful in your master domain user naming convention.

  Create the domain master's .qmail files with the following commands.
  Add any other system aliases at this point.  For example, webmaster or

  echo "" > /home/d/domain1/.qmail-mailer-daemon
  echo "" > /home/d/domain1/.qmail-postmaster
  echo "" > /home/d/domain1/.qmail-root

  Create the domain master's .qmail-default file.  This will filter all
  mail to the virtual domain.

  echo "| /usr/local/bin/virtmailfilter" > /home/d/domain1/.qmail-default

  9.4.4.  Tcpserver

  Qmail requires a special pop that can support the Maildir format.  The
  pop program has to be virtualized.  The author of Qmail recommends
  using tcpserver (an inetd replacement) with Qmail so my examples use
  tcpserver and NOT inetd.

  Tcpserver does not require a config file.  All the information can be
  passed to it via the command line.  Here is the tcpserver.init file
  that you would use for the mail daemon and popper:


  . /etc/rc.d/init.d/functions

  QMAILDUSER=`grep qmaild /etc/passwd | cut -d: -f3`
  QMAILDGROUP=`grep qmaild /etc/passwd | cut -d: -f4`

  # See how we were called.
  case "$1" in
          echo -n "Starting tcpserver: "
          tcpserver -u 0 -g 0 0 pop-3 /usr/local/bin/virtuald \
                  /virtual/conf.pop qmail-popup \
                  /bin/checkpassword /bin/qmail-pop3d Maildir &
          echo -n "pop "
          tcpserver -u $QMAILDUSER -g $QMAILDGROUP 0 smtp \
                  /var/qmail/bin/qmail-smtpd &
          echo -n "qmail "
          touch /var/lock/subsys/tcpserver
          echo -n "Stopping tcpserver: "
          killall -TERM tcpserver
          echo -n "killing "
          rm -f /var/lock/subsys/tcpserver
          echo "Usage: tcpserver {start|stop}"
          exit 1

  exit 0

  9.4.5.  Qmail.init

  You can use the standard Qmail init script provided.  Qmail comes with
  very good documentation describing how to set this up.

  9.4.6.  Source

  You require two other programs to get virtual mail working with Qmail.
  They are virtmailfilter and virtmaildelivery.  This is the C source to
  virtmailfilter.  It should be installed in /usr/local/bin with
  permissions 4750, user root, and group nofiles.

  #include <sys/wait.h>
  #include <unistd.h>
  #include <string.h>
  #include <stdlib.h>
  #include <stdio.h>
  #include <ctype.h>
  #include <pwd.h>

  #define VIRTPRE                 "/virtual"

  #define VIRTPWFILE              "etc/passwd"
  #define VIRTDELIVERY            "/usr/local/bin/virtmaildelivery"
  #define VIRTDELIVERY0           "virtmaildelivery"

  #define PERM                    100
  #define TEMP                    111
  #define BUFSIZE                 8192

  int main(int argc,char **argv)
          char *username,*usernameptr,*domain,*domainptr,*homedir;
          char virtpath[BUFSIZE];
          struct passwd *p;
          FILE *fppw;
          int status;
          gid_t gid;
          pid_t pid;

          if (!(username=getenv("EXT")))
                  fprintf(stdout,"environment variable EXT not set\n");


          if (!(domain=getenv("HOST")))
                  fprintf(stdout,"environment variable HOST not set\n");

                  if (*domainptr=='.' && *(domainptr+1)=='.')
                          fprintf(stdout,"environment variable HOST has ..\n");
                  if (*domainptr=='/')
                          fprintf(stdout,"environment variable HOST has /\n");


                  if (chdir(virtpath)>=0)
                  if (!(domainptr=strchr(domainptr,'.')))
                          fprintf(stdout,"domain failed: %s\n",domain);


          if (!(fppw=fopen(VIRTPWFILE,"r+")))
                  fprintf(stdout,"fopen failed: %s\n",VIRTPWFILE);

                  if (!strcmp(p->pw_name,username))

          if (!p)
                  fprintf(stdout,"user %s: not exist\n",username);

          if (fclose(fppw)==EOF)
                  fprintf(stdout,"fclose failed\n");


          if (setgid(gid)<0 || setuid(p->pw_uid)<0)
                  fprintf(stdout,"setuid/setgid failed\n");

                  case -1:
                          fprintf(stdout,"fork failed\n");
                  case 0:
                          if (execl(VIRTDELIVERY,VIRTDELIVERY0,username,homedir,NULL)<0)
                                  fprintf(stdout,"execl failed\n");
                          if (wait(&status)<0)
                                  fprintf(stdout,"wait failed\n");
                          if (!WIFEXITED(status))
                                  fprintf(stdout,"child did not exit normally\n");

  9.4.7.  Source

  You require two other programs to get virtual mail working with Qmail.
  They are virtmailfilter and virtmaildelivery.  This is the C source to
  virtmaildelivery.  It should be installed in /usr/local/bin with
  permissions 0755, user root, and group root.

  #include <sys/stat.h>
  #include <sys/file.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  #include <stdio.h>
  #include <errno.h>
  #include <time.h>

  #define TEMP                    111
  #define BUFSIZE                 8192
  #define ATTEMPTS                10

  int main(int argc,char **argv)
          char *user,*homedir,*dtline,*rpline,buffer[BUFSIZE],*p,mail[BUFSIZE];
          char maildir[BUFSIZE],newmaildir[BUFSIZE],host[BUFSIZE];
          int fd,n,nl,i,retval;
          struct stat statp;
          time_t thetime;
          pid_t pid;
          FILE *fp;


          if (!argv[1])
                  fprintf(stdout,"invalid arguments: need username\n");


          if (!argv[2])
                  fprintf(stdout,"invalid arguments: need home directory\n");


          if (!(dtline=getenv("DTLINE")))
                  fprintf(stdout,"environment variable DTLINE not set\n");

          if (!(rpline=getenv("RPLINE")))
                  fprintf(stdout,"environment variable RPLINE not set\n");

          while (*homedir=='/')
          if (chdir(maildir)<0)
                  fprintf(stdout,"chdir failed: %s\n",maildir);

          if (gethostname(host,BUFSIZE)<0)
                  fprintf(stdout,"gethostname failed\n");

                  if (errno==ENOENT)

          if (i>=ATTEMPTS)
                  fprintf(stdout,"could not create %s\n",mail);

          if (!(fp=fopen(mail,"w+")))
                  fprintf(stdout,"fopen failed: %s\n",mail);
                  retval=TEMP; goto unlinkit;


          if (fprintf(fp,"%s",rpline)<0)
                  fprintf(stdout,"fprintf failed\n");
                  retval=TEMP; goto unlinkit;

          if (fprintf(fp,"%s",dtline)<0)
                  fprintf(stdout,"fprintf failed\n");
                  retval=TEMP; goto unlinkit;


                  if (!strncmp(p,"From ",5))
                          if (fputc('>',fp)<0)
                                  fprintf(stdout,"fputc failed\n");
                                  retval=TEMP; goto unlinkit;

                  if (fprintf(fp,"%s",buffer)<0)
                          fprintf(stdout,"fprintf failed\n");
                          retval=TEMP; goto unlinkit;

          if (*p=='\n')
                  if (fputc('\n',fp)<0)
                          fprintf(stdout,"fputc failed\n");
                          retval=TEMP; goto unlinkit;

          if (fsync(fd)<0)
                  fprintf(stdout,"fsync failed\n");
                  retval=TEMP; goto unlinkit;

          if (fclose(fp)==EOF)
                  fprintf(stdout,"fclose failed\n");
                  retval=TEMP; goto unlinkit;

          if (link(mail,newmaildir)<0)
                  fprintf(stdout,"link failed: %s %s\n",mail,newmaildir);
                  retval=TEMP; goto unlinkit;

          if (unlink(mail)<0)
                  fprintf(stdout,"unlink failed: %s\n",mail);


  9.5.  Acknowledgement

  Thank you Vicente Gonzalez ( for helping make the
  Qmail solution possible.  You can certainly mail your thanks to Vince,
  however all questions and comments including issues regarding Qmail,
  about this HOWTO should continue to be directed to me.

  10.  Virtual Samba

  10.1.  Setup

  Virtual SAMBA is very simple to install.  Make sure that the following
  files are setup properly:

  o  /virtual/ FILE

  o  /virtual/ DIRECTORY

  o  /virtual/ DIRECTORY

  o  /usr/local/bin/virtsmbstatus SYMLINK /usr/local/bin/virtexec

  10.2.  Inetd

  Edit /etc/inetd.conf

  vi /etc/inetd.conf # Add this line
  netbios-ssn stream tcp nowait root /usr/local/bin/virtuald \
          virtuald /virtual/conf.smbd smbd

  10.3.  Smb.init

  An smb.init file is not needed since the server is run through inetd.

  11.  Virtual Other

  Any other service should be a similar procedure.

  o  Run virtfs to add the binaries and libraries to the virtual

  o  Add it to /etc/inetd.conf.

  o  Create a /virtual/conf.service file.

  o  Create any virtual scripts that need to be made.

  12.  Conclusion

  Those are all the steps you need. Again mail any responses to Computer
  Resource Center.  If you have a question or an update to the document
  let me know and I will add it.

  The document has met with a very good response.  I thank all the
  people who sent me questions as they are helping to shape the document
  to meet the needs of users everywhere.  Before you ask a question I
  urge you to read the FAQ to see if it has been already asked and
  answered.  Thanks again.  Brian

  13.  FAQ

  Q1. I created sendmail.init and syslogd.init.  I put them in
  /usr/local/bin and tried to run them but I got errors.

  A1. These files are called init scripts.  They are run by the program
  init when your computer boots.  They do not go with the /usr/local
  binaries.  Consult the Linux System Administrators Guide or the Linux
  Getting Started Guide for information on how to use the init scripts

  Q2. I put these lines into /etc/


  And I got really stange output.  Why?

  A2. You do not put these lines directly in /etc/  The file was written to be easy for sendmail to understand and
  hard for humans to read.  Therefore, to make it easy to configure we
  use a program called m4 and its macro capabilities to create the file.  The FEATURE lines are actually macros that expand
  to sendmail configuration statements.   See the sendmail docs on how
  to configure sendmail through this method.  Also note that you create
  a main /etc/ file and the virtfs script then copies this to
  /virtual/  Then you edit that
  file to respond as your domain.

  Q3. Where do I get virtuald, what is it, and how do I use it?

  A3. Virtuald is C source that I wrote to run a virtual service.  It is
  included with this HOWTO.  You compile it like a normal C program
   make virtuald .  The resulting binary is placed into /usr/local/bin.
  Add lines to /etc/inetd.conf that use virtuald as a wrapper to a
  normal network server program.

  Q4. I do not have dialog installed on my system?

  A4. Dialog is a program that allows you to put dialog pop up windows
  into your shell scripts.  It is required for my virtual shell script
  examples to work.  You can get a copy of dialog at sunsite.  It
  compiles very easily and should be no problem to install.

  Q5. How can I know if virtual syslogd is working?

  A5. When virtuald runs it should output the following messages to
  syslogd (/var/log/messages):

  Nov 19 17:21:07 virtual virtuald[10223]: Virtuald Starting: $Revision: 1.49 $
  Nov 19 17:21:07 virtual virtuald[10223]: Incoming ip:
  Nov 19 17:21:07 virtual virtuald[10223]: Chroot dir: /virtual/

  The  Chroot  dir message is sent by virtuald after the  chroot  system
  call is performed.  If this message appears virtual syslogd is
  working.   If the service you are virtualizing logs messages to
  syslogd and you see them that is also a sign that virtual syslogd is
  correctly setup.

  Note that if you have not turned on the compile time option
  VERBOSELOG, virtuald will not log at all.  The only way to tell if
  virtual syslogd is working at that point is if the daemon you are
  virtualizing independently logs something to syslogd.

  Q6.  How can I setup quotas across virtual filesystems?

  A6.  You setup quotas like you would normally.  See the Quota mini-
  HOWTO.  However, you have to make sure there are no uid conflicts
  across domains.  If there are conflicts you will have users sharing a
  quota.  Set aside a range of uid's that you know will have quota's
  enabled and tell your domains that they cannot have any users in that
  range except the ones registered to have a quota.

  Q7.  What is this \ notation in all the inetd.conf entries?

  A7.  That is just a method of breaking up config files across two
  lines.  I did that so the line would word wrap in a nice place.  You
  can just ignore the \ and join the two lines back together.

  Q8.  When I run passwd or other login programs I get  permission
  denied .  When I run FTP or su I get  no modules loaded for service
  XXX .  Why?

  A8.  Those are PAM error messages.  I wrote these scripts before PAM
  was out.  My virtfs script does not copy /etc/pam.d,
  /usr/lib/cracklib_dict.*, /lib/security or any of the other files PAM
  requires.  PAM needs these to function.  If you edit my virtfs script
  to copy these files the problem will go away.

  Q9.  Can virtuald work with tcpd hosts.allow and hosts.deny files?

  A9.  Yes it can with some modifications.

  First the source has to be changed in two places.

  This has to be inserted where the arguments are checked.

          if (!argv[3])
                  syslog(LOG_ERR,"invalid arguments: no program to run");

  The exec line has to be changed from:

          if (execvp(argv[2],argv+2)<0)


          if (execvp(argv[2],argv+3)<0)

  Second the inetd.conf lines have to be changed from:

  ftp stream tcp nowait root /usr/local/bin/virtuald \
          virtuald /virtual/conf.ftp wu.ftpd -l -a


  ftp stream tcp nowait root /usr/local/bin/virtuald \
          virtuald /virtual/conf.ftp tcpd wu.ftpd -l -a

  Third edit the /virtual/ and
  /virtual/ files accordingly.

  Q10.  Can my virtual hosts run CGI's?

  A10.  Yes they can but I recommend putting the /cgi-bin in a place
  outside of the  chroot  that only you have access to.  For example,
  /var/www/cgi-bin/  Giving clients access to /cgi-bin is
  giving them the opportunity to run programs on your sever.  This is a
  big security hole.  Be careful.  I do not let any cgi run on my
  systems that I have not personally inspected for bugs.

  Q11.  My configuration files are different from your examples.   What
  do I do?

  A11.  There are two basic configuration styles: SystemV and BSD.  The
  examples provided in the HOWTO are based on SystemV style
  configuration files.  Virtual services works equally well on either
  system.  For information on BSD style configuration files consult the
  origin of your distribution or the nearest LDP site.

  Q12.  I sent you mail and have not heard a response from you or your
  response took a long time.  Why?

  A12.  Probably because you did not put VIRTSERVICES HOWTO in your
  subject header.  Please bear in mind that I am a network administrator
  and that among the other things I do in my 20 hour days is
  administering my own virtual boxes and those of my clients.  Mail that
  is properly addressed is always responded to within two or three days.
  Mail that is improperly addressed does not get filtered into my
  VIRTSERVICES mailbox and can lie around unnoticed for days or weeks.

  Q13.  Does virtuald work under 100Mbit?

  A13   The speed of the network card is unrelated to whether virtuald
  will work or not.  Try making sure that your server works under 10Mbit
  and that your 100Mbit network card works normally without a virtual
  Q14.  Should I use sendmail's virthost table?

  A14.  No.  That is sendmail's feature to accept info for multiple
  domains.  Virtuald gives each sendmail its own separate  chroot
  environment.  Install virtuald and then configure sendmail like you
  would normally for each domain.

  Q15.  Can I setup virtual telnet on my machine?  What about creating a
  virtual root account so clients can administer their own domains?

  A15.  These questions come to me quite often and to be honest, I am
  getting a bit tired of them.  The answer, as stated numerous times in
  the documentation, is that any service run through inetd can be
  virtualized using virtuald so there is nothing to stop you from doing
  either of the above.  Nothing except common sense.  Whatever benefits
  you might derive from allowing telnet are heavily outweighed by the
  cost to the virtual box (and thus the sites you are supposed to be
  hosting in a responsible manner) in terms of security.  Here are just
  a few issues involved:

  o  In order to completely fool an incoming telnet session you have to
     hack the kernel to get multiple procs working, reset your source IP
     address for outgoing connections, fool gethostname so it uses the
     virtual hostname and not the system hostname, etc.  If you are an
     advanced user then by all means hack the kernel.  For the newbie I
     do not recommend it.

  o  By allowing users to come into your box via telnet you allow them
     to run arbitrary programs.  Through known hacks you can get root
     and cause damage to the system.

  o  Giving a root telnet account on a virtual box is very bad.  A root
     virtual user can still read raw device files which nullifies the
     chroot , shutdown the system, and can kill other processes on the

  o  The programs that these telnet sessions are running take up
     valuable CPU time that the network services could be using.

  o  Telnet is an insecure network service.  Plain text passwords are
     sent out over the net.  If a malicious user gets this password
     he/she can use the above mentioned attacks to harm your system.

  o  Your virtual environments will have to be bigger.  You will need
     more shared libraries, more configuration files, and more binaries.
     A six gigabyte disk can run out of space really fast.

  The bottom line is that allowing login's on a virtual box is a really
  bad idea.  If permitted, every site hosted on that machine is at risk.
  If you want to allow a site holder to administer users then you are
  advised to write (not script) the code necessary to run the virtual
  processes that allow them to add, delete or modify users upon login
  through ssh.  This should be completely menu driven, should never
  allow a console and should not run as root.  In order to accomplish
  this you will have to change ownership of the pertinent files from
  root to some other user.  If done in this manner it is marginally safe
  to incorporate into a virtual machine.  There is never an acceptable
  time to allow root login's either through telnet or ssh.  Doing so is
  simply an invitation to disaster.  If there is an overwhelming reason
  to run telnet then the site should be hosted on a dedicated machine
  where the only risk is to the individual site.  No responsible
  administrator would ever do otherwise and so I will waste no more time
  on this issue.

  Q16.  Is there an rpm, tar, web site, mailing list, etc. associated
  with virtuald and the Virtual-Services HOWTO?

  A16.  Currently there is nothing like that available.  This HOWTO is
  the only source of information to everything I do concerning this
  project.  I find the HOWTO to be fairly self contained making the need
  for other pieces of information superfluous.

  Q17.  When I try to run virtexec as a regular user I get  chroot:
  operation not permitted .  Why?

  A17.   Chroot  is a root restricted system call.  Only the superuser
  can execute it.  The virtexec script runs the  chroot  program which
  is why you need to be root in order to run it.

  Q18.  I setup pop and sendmail but popping mail does not seem to work.
  How come?

  A18.  Some pop programs come with /usr/spool/mail as their place for
  mail files.  I know that qpop has to be manually editted to fix this.
  Either recompile the source to your program or symlink
  /virtual/ to /virtual/

  Q19.  I did not use the program mentioned in your HOWTO, I used
  program XXX.  It does not work.  Why?

  A19.  I tried to make sure to use the most generic of each server in
  my examples.  However, I know that everyone has their favorite version
  of each server.   Send me as much information as possible and I will
  try to figure out how to solve your problem and document it in the
  FAQ.  The most important piece of information to send me is where to
  get the version of the software you are running (in the form

  Q20.  When I run virtexec is says  symlink not a virt function .  What
  does this mean and how do I fix it?

  A20.  Virtexec is a program that will take its zero argument, strip
  off the first four characters, and run the remaining name in the
  virtual environment.  For example, virtpasswd runs passwd.  If the
  first four characters that it strips off are not  virt  it complains
  and outputs that error message.  Virtexec is written in shell script
  and should be fairly simple to follow.  Refer to the manual pages on
  bash or whatever shell you run for questions about shell script

  Q21.  I have a question about Qmail, SAMBA, Apache, etc. that is
  unrelated to the virtuald setup or how the package interfaces to

  A21.  All the packages described here are fully documented.  Some even
  have full web sites like dedicated to them.
  Please consult them about questions dealing with the package that are
  unrelated to their virtual hosting functionality.

  Q22.  I have several domain aliases to but mail keeps
  bouncing from the aliases.   How come?

  A22.  Virtmaildelivery relies on the environment variables passed to
  it to determine which /virtual/ directory to deliver to.
  It does not perform any DNS lookups to determine the address of the
  mail.  However, if the address is,
  virtmaildelivery will first try that address and then
  and then and then com in that order until either a match
  happens or there is no domain name left.

  However, if you have domain aliases that are not subdomains of one
  another you have to create symlinks like so:

  cd /virtual
  ln -s

  That way virtmaildelivery will be fooled into thinking that both
  directories exist even though one is a symlink and mail will be able
  to be delivered to or  Note
  that virtexec will list both of the domains in the dialog box when
  your run it.  You can choose either one since they will be the same
  virtual filesystem.

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