networking

How to share a folder between the VMware host and guest?

May
01

If you need to share a holder between your Windows host and Linux guest, you may use native VMware folder sharing available on VMware Workstation or VMware Player. To allow folder sharing, you must install VMware Tools on the guest operating system. I've used a VMware Player to demonstrate the configuration options, but WMware Workstation 8 will follow the similar steps.

Prerequisites
■ VMware Tools installer is written in Perl, verify that Perl is installed in the guest operating system.

1. Go to Virtual Machine -> Virtual Machine Settings ....

My serial printer doesn't work. What shall I do?

Feb
04

Serial printers generally do not require a device driver to work in a desired software application. If POS software cannot print directly to the serial printer, it is preferable to make sure we can print from the running operating system such as Windows or Linux. Here are a few things to do to diagnose serial printer problem.

Use the right cable. When trying to connect DTE (PC) to a DTE (such as printer), you'll need to use a null model cable. For information about RS232 Cabling, refer RS232 Cables, Wiring and Pinouts.

TCP Sweep - What is causing it?

Feb
04

Running a company as a reseller web host, you'll often receive an email from your upstream provider reporting security violations. If you do not correct the problem in a timely manner, your upstream provider may block inbound and outbound traffic from the affected server.

Today, we received a security report from Savvis indicating that one of our Windows 2003 server is sweeping TCP port 445. This obviously violates their "Acceptance Use Policy". Here is the snippet of their log entry.

How do I extract information from an SSL key and certificate?

Feb
04

An SSL certificate contains the information about issuer, valid dates, subject and other cryptic information. The openssl x509 subcommand may be used to retrieve those information from a SSL certificate.

# The "-text" option will output full breadth of certificate information.
bash# openssl x509 -text -in server.crt

# The "-issuer" option will show issuer.
bash# openssl x509 -noout -in server.crt -issuer

# The "-subject" option will show Organizational information.
bash# openssl x509 -noout -in server.crt -subject

Install spamassassin with sendmail

Feb
04

Documentation http://spamassassin.apache.org/

1. Install spamassassin on the server

# yum install spamassassin

2. Install required perl CPAN modules

# perl -MCPAN -e shell
cpan> install Digest::SHA1
cpan> install HTML::Parser
cpan> Install option perl modules...

2. Edit spamassassin configuration in /etc/mail/spamassassin/local.cf .

Enable Out-Of-Office replies to the Internet

Feb
04

By default, Microsoft Exchange Server 2003 Out-of-Office replies to the Internet is disabled. This is done to disallow Out-of-Office auto-replies to be sent outside of the organization to prevent outsider to learn when users are out of the office.

To enable Out-Of-Office replies to the Internet:

1. On the Exchange Server machine, go to Start - Programs - Microsoft Exchange - Systems Manager.

2. Double click Global Settings, and then click Internet Message Formats.

Setting mail header for a foreign language

Feb
04

Depending on the client's regional settings and an ability to read foreign language on the client's computer, emails sent using traditional text/plain mail header may not be readable by foreign receipients. To allow mails to be sent in correct format, the following mail headers must be set in addition to From, CC and BCC mail headers.

MIME-Version: 1.0
Content-Type: text/plain; charset=ks_c_5601-1987
Content-Transfer-Encoding: quoted-printable

Exchange Server and firewall

Feb
04

An Exchange Mail user who has a problem establishing a connection to the server may have one or more TCP ports blocked. The blockage may be from computer or router firewall, or your Internet provider may simply blocks the ports needed by the Exchange Server such as TCP port 135. Various Internet providers, including Cox, Comcast and Verizon have blocked the port 135 at one point and they may still do.

To determine whether the TCP port is blocked, you may simply use 'telnet' command to test out the port. For example, if your server IP is 1.2.3.4 and the port in question is 135...

What is Wi-Fi and how secure is it?

Feb
04

1. Overview

Wi-Fi, (or Wireless Fidelity) is a wireless LAN technology which allows Wi-Fi equipped computers to connect to the Internet from anywhere within the range of a base station. Wi-Fi encompasses a family of specifications within the IEEE 802.11 standard. These include 802.11b (the most popular, at 11Mbps, with typical range of up to 300 feet), 802.11a (54Mbps, but at a shorter range) and 802.11g (combining the speed of "a" while keeping the range of "b").

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