Questions and Answers

Amy Rich

In last month's issue, we had a question regarding the differences between SAN and NAS. The answer given had the explanations of the two reversed. NAS (like NetApp) are storage devices attached to the network and SAN (like EMC) are storage devices attached to a computer via fiber/SCSI. We regret any confusion resulting from this error -- the editors.

Q I'm trying to put a Perl script into my .forward to handle a bunch of spam that I get. My .forward looks like the following:

|/home/jr/scripts/spamcull.pl

A You may want to consider something like Procmail (http://www.procmail.org/) to do spam culling for you instead of trying to roll your own script. procmail is a powerful recipe-based filter that you can stick in as the LDA or call from .forward. As to why you're getting "Service Unavailable", this sounds like it may be a smrsh problem. Are you using smrsh in conjunction with Sendmail? If so, you may need to symlink your script into your smrsh directory (often /etc/smrsh or /etc/mail/smrsh).

Q I want to write a quick Perl script that takes a bunch of file names, reads them in, and stores them. I know how to do this sequentially, but it seems like this would be the right place to put in a function. Is there a quick "read and assign" function to which you can point me?

A You'll want to iterate through a loop of file names and perhaps do an array of arrays for the actual assignments in the main loop. Your read/assign function will probably look something like the following, however:

sub readfile {
  my ($fname) = shift;  # name of the file, passed from the main loop
  local (*FILEH);       # the file handle

  open (FILEH, $fname) || die "Can't open $fname: $!\n"; # open or die
  my (@filea) = <FILEH>;      # read in the file to an array
  close (FILEH);              # close the file
  return @filea;              # return the array
}

A I'd consider Brian Kernighan and Dennis Ritchie fairly authoritative, and the UNIX FAQ (http://www.faqs.org/faqs/unix-faq/faq/part1/) has the following to say:

rc (as in ".cshrc" or "/etc/rc") = "RunCom"

"rc" derives from "runcom", from the MIT CTSS system, ca. 1965.

"There was a facility that would execute a bunch of commands stored in a file; it was called "runcom" for "run commands", and the file began to be called "a runcom."

"rc" in Unix is a fossil from that usage."

Brian Kernighan & Dennis Ritchie, as told to Vicki Brown

Q We are using jumpstart to automate our Solaris installs. At the end, the jumpstart finish script installs a script that runs after reboot to install the custom software packages via executing pkgadd commands. These pkgadd commands in turn have pre- and post-install scripts and want to interact with the installer. When trying to install, the pkgadd has errors and fail because the pre- and post-install scripts don't get that user interaction. Do you know how I could automate this?

A You can have pkgadd use an alternate administrative file and do installs without manual intervention. Your pkgadd command will look something like the following:

pkgadd -n -a $adminfile $package

mail=
instance=quit
partial=nocheck
runlevel=nocheck
idepend=nocheck
rdepend=nocheck
space=ask
setuid=nocheck
conflict=nocheck
action=nocheck
basedir=default

mail=
instance=unique
partial=ask
runlevel=ask
idepend=ask
rdepend=ask
space=ask
setuid=ask
conflict=ask
action=ask
basedir=default

Q I have a script that I want to run unattended, but occasionally it may prompt the user for input. I'm never sure how many times it will prompt (it changes based on the OS it's running on), but the answer should always be "yes". Is there an easy way to automate this so that no one has to sit at the window and input "yes" at random times?

A If your answer should always be yes, it sounds like you may just be better off removing the conditions from the script. However, there are a couple ways you can automate this. For flexibility's sake (in case you ever want to answer "no" or something else), you could wrap your script with expect. If you're sure you're always going to say "yes", you can just pipe the output of the yes program to your script:

yes yes | ./script

Q How can I tell which Perl modules I have installed with my Perl distribution?

A You can get a complete listing of the third-party modules installed by doing a:

perldoc perllocal

  Mon Apr  2 13:33:21 2001: 'Module' the CPAN manpage

o   `installed into: /usr/local/lib/perl5/5.6.0'

o   `LINKTYPE: dynamic'

o   `VERSION: 1.59'


o   `EXE_FILES: cpan'

A fetchmail must have an MTA to connect to in order to deliver your mail. What you can do is bind Sendmail to the loopback interface only, and not your public (or private) interface. In your fetchmailrc file, set the following so that fetchmail tries to connect to the loopback interface instead of another interface on your machine. It should try the loopback interface anyway if you're not using ETRN, ODMR, or Kerberos auth (where the domain name is added), but it doesn't hurt to explicitly set it here:

smtphost 127.0.0.1

FEATURE(`no_default_msa')dnl
DAEMON_OPTIONS(`Name=MTA',`Addr=127.0.0.1')dnl

Q On a Solaris 7 SPARC machine, how do I increase the security of the TCP random number generator?

A If you're talking about the way selected TCP ports are randomized, you want to change the file /etc/default/inetinit to be the following:

# @(#)inetinit.dfl 1.2 97/05/08
#
# TCP_STRONG_ISS sets the TCP initial sequence number generation 
# parameters.
# Set TCP_STRONG_ISS to be:
#     0 = Old-fashioned sequential initial sequence number generation.
#     1 = Improved sequential generation, with random variance in increment.
#     2 = RFC 1948 sequence number generation, unique-per-connection-ID.
#
TCP_STRONG_ISS=2

Q For security purposes, I want to track down all of the world-writable files on my AIX system. How would I go about this?

A The best tool for this is find. You can search for world-writable files with the following command (you should be root or you'll receive a lot of "permission denied" errors):

find / -type f -perm +0002 -print

find / -type f -perm +0022 -print

Q I have an Ultra 10 running Solaris 8. When I take a look at the routing table, I see a lot of routes that are seemingly useless. If I flush the routing table, most of them disappear but then come back again later. There's obviously something messing with the routing table. What is it, and how do I stop it?

A There are two likely candidates for your problem. Solaris comes with two binaries that may start at boot time and will edit your routing table on the fly -- in.routed and in.rdisc. You can shut off routed by giving your machine an explicit default route in /etc/defaultrouter. The router discovery daemon (rdisc) is started if you have multiple interfaces not configured by DHCP. You can turn it off by touching the file /etc/notrouter. Both of these processes are started as part of /etc/init.d/inetinit (hard-linked to by /etc/rc2.d/S69inet). Take a look at the man pages for in.rdisc, in.routed, and defaultrouter and the /etc/init.d/inetinit script for more information.

Q I'm running Sendmail 8.11.3, and I'm seeing a huge number of Sendmail processes sending mail outbound. Is there some way I can cut down on the number of processes Sendmail forks? This is killing my poor machine.

A You can limit the number of daemon children with MaxDaemonChildren. You'll probably also want to queue all outgoing mail and then run the queue to deliver mail. This will order your processes sequentially instead of forking for every new outbound mail delivery. Add the following to your mc file and rebuild your cf file (adjust the maximum number of processes and the minimum queue age to suit your machine):

define(`confMAX_DAEMON_CHILDREN',`10')dnl
define(`confDELIVERY_MODE',`queueonly')dnl
define(`confMIN_QUEUE_AGE',`10m')dnl

When you start Sendmail, you'll want to run the queue at some frequent interval (say every 10 minutes), so your mail doesn't sit on your machine for too long:

sendmail -q10m -bd

Q I'm running a 4.3-Release FreeBSD machine. Hooked to it is an Overland Data Loader Express DLT Tape Library. I can access whatever tape I happen to load manually. Is there any way to have it automatically load a specific tape?

A You'll want to take a look at the man page for chio. This should handle most generic loaders. For example, you can move slot 2 to drive 0, do a dump of /, /usr, /var, and /home, and then move the tape back out to its original slot with the following commands:

chio move slot 2 drive 0
dump 0auf /dev/nrsa0 /
dump 0auf /dev/nrsa0 /usr
dump 0auf /dev/nrsa0 /var
dump 0auf /dev/nrsa0 /home
mt -f /dev/nrsa0 offline
chio move drive 0 slot 2

http://www.freebsd.org/doc/en_US.ISO_8859-1/books/handbook/kernelconfig.html

A You can take a look at Sun's spare parts list, located at:

http://www.sun.com/ibb/spares/parts-list/TOC.html

http://store.sun.com/

A You don't actually have to remove Sendmail. Later versions of FreeBSD have a config file called /etc/mail/mailer.conf that determines what binary gets called when the following programs are run:

sendmail
send-mail
mailq
newaliases

cd /usr/ports/mail/postfix
make install

http://www.freebsd.org/doc/en_US.ISO_8859-1/books/handbook/ports.html

NO_SENDMAIL=yes

sendmail_enable="NO"

$ echo "this is a test" > foo
$ ls foo
$
$ cat foo
this is a test
$ mv foo bar
$ ls bar
$

$ ps -elf
/usr/local/bin/bash: ps: cannot execute

A It looks as though you've been hacked and someone has installed an improperly implemented rootkit. Instead of just hiding some files with ls, it's hiding them all, and instead of hiding some processes with ps, it's just refusing to execute (probably installed with the wrong permissions). You'll want to find out how they broke in, when they broke in, and restore from known backups and patch from there. I hope you've been doing some sort of security monitoring all along, or it's going to be very difficult to track down the hole and fix it. You may just be better off upgrading to Solaris 7 (the IPX isn't supported for Solaris 8) and restoring only your data.

Q I'm trying to script some jumpstart stuff to comment out lines in a Solaris startup file. The text of the file looks something like:

echo "Setting default...
<some other lines>
    -netmask 240

A You can use sed to do this if you have unique begin and end strings in the file. Try the following (where $file is the file you want to modify):

sed -e '/^echo "Setting default/,/^    -netmask 240/ s/^/#/' \
 < $file > /tmp/newfile
cp /tmp/newfile $file
rm -f /tmp/newfile

sed -e '/^echo "Setting default/,/^ -netmask 240/d' \
 < $file > /tmp/newfile cp /tmp/newfile $file rm -f /tmp/newfile