Re: how to start ftp daemon - the whole scoop

["Dr. P. Sriram" <sriram@xxxxxxxxxxxxxxxxxx>]

On Mon, 7 Feb 2000, Binand Raj S. wrote:
[replying to doubt raised by  kamesh jayachandran]
> So far as I know, neither ftpd nor telnetd are started at system boot
> time. :-)

well, smily apart, it depends. if a machine is used as an ftp server
(repository), i will bet ftpd is started as part of boot sequence. so
also, you can assume that a web server will have the appropriate
daemon (apache httpd or whatever) started at boot time. here is how the
services work.

first, there is the file /etc/services. this file lists symbolic names for
services and the port/socket (and protocols) associated with the service. 
for example, port 23 is used for (incoming) telnet connections, port 80
for www services etc. if you want to have your own tcp/ip service, you may
add your own service/port entry to this file. next, one has to decide
whether a particular service is to be provided as a standalone (background
daemon) or as a start-on-demand call through inetd. inetd will start the
appropriate server daemon on demand and upon completion of the job, the
daemon will quit. the next time a connection is made, inetd will go over
the process again. for services like www and receiving mail, it is
generally preferred to use a standalone daemon; otherwise (in the case of
www), every time a user requests a service (a html page), the (www) daemon
will be started fresh and response is likely to be slow. on the other
hand, leaving an in.ftpd running on a workstation type machine is simply
going to be carrying an idle daemon most of the time. hence, depending on
the usage, one has to choose the method of invocation (direct or through
inetd). standalone daemons are started as part of the boot sequence. inetd
invoked daemons are listed as entries in /etc/inetd.conf (some flavours of
unix use /etc/servers). the inetd.conf file lists the symbolic name of the
service, some options associated with it and also the name of the daemon
that will actually provide the service. these days, it is customary to use
the tcp wrapper to control access to services offered by inetd. in that
case, the appropriate entry in inetd.conf will invoke tcpd and use the
actual name of the daemon as an argument to tcpd. the tcpd wrapper uses
the hosts.allow and hosts.deny files to determine whether a service is to
be offered or not (or whatever other action is to be taken). due to the
various things it does, sendmail is rather slow to start and hence, it is
usually not a good idea to start sendmail from inetd.conf. otherwise, it
all depends on the application of the machine.

sriram


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