Thus, server uptime is very important and the goal of system administrators is to have minimal or no downtime at all. A particular downtime could lead to a loss of revenue or profit. There is some mechanism developed that will minimize the impact on the site visitors whenever a glitch is the computer system or computer network happens. System fail over, server load balancing, site redirection is just some of the techniques employed.

Monitoring server uptime in order to minimize downtime and maintain availability could be done by server monitoring software. This software could send an automatic alert through email, pager, and messengers when there is a problem with the computer system, service, device, switches, and more. Computer specialist will be notified immediately whenever the website or server is down or having an access problem.

We’ve use Nagios open source web monitoring solution software for creating a comprehensive IT infrastructure monitoring. Depending on service provided by the server the Nagios monitoring software can check different protocols like HTTPS, HTTP, FTP, SMTP, IMAP, POP3, DNS, Telnet, SSL, TCP at regular intervals. Checking can be done for multiple servers with various operating systems like Linux, Windows and others. A small client application could be installed on the tracked server for detailed ports and services scanning

Having an automatic alert from a server monitoring software makes a difference in reducing downtimes. It also improves customer trust and reduces business loss.

Many have frowned before on iPhone, iPad, and iPod Touch, for the lack of multitasking features. The recent iOS 4 update though brought multitasking to iPhone and its siblings. Google’s open source mobile device operating system Android has been getting more support from developers. On the other hand, application developers face some challenges working on Apple’s proprietary OS.

The consequence though are the increasing security threats from malware and viruses. Smart phones are becoming powerful and hackers are attracted to these mini computers. Android open source mobile device apps store has thousands of apps available. Security expert research shows that some of these mobile device applications are devious malware.

Downloading free applications, especially on Android based mobile phones should be done carefully. Mobile devices should have a reliable protection program. It’s a wise investment, especially when the smart phones are used to sync data with corporate servers. Malware and virus threats on mobile devices are surely for real.

Nobody can really say that Google Chrome security features are better than say, Windows, Mac OS or Linux. Google has moved to push Chromium OS for netbooks and mobile devices. The security is a key feature and a critical factor that have made Google a success. The modular architecture for Chrome has made it a popular choice over other browsers, which is the same rendering engine is used in the Chromium OS.

Google’s lightweight Chromium OS, is geared toward laptops, netbooks and mobile devices. All applications running in Chromium OS will be taking place within the browser and much of the data storage would be located online. This would mean no conventional desktop applications to install and manage. All Chromium OS security updates are immediately done. This makes Google’s open source lightweight Chromium OS ideal for netbooks and mobile devices.

First is to change the hostname without restarting the computer. This could be achieved using the hostname command as follows:
$sudo hostname newhost.domain.com

Second is to have the hostname stay even when the RedHat Linux server is rebooted. This could be done by editing hostname found in the system configuration network file as follows:
$sudo vi /etc/sysconfig/network

Lastly is to check and change the hosts file which sometimes contain old hostname. This could be done by editing the hosts file found under the “etc” folder as follows:
$sudo vi /etc/hosts

The above steps are the way I configure the RedHat Linux test server environment hostname. I find that conflicts can be avoided when hostnames are changed prior to plugging a test server to the working network.

In Linux, a way of finding the location of a file is through the use of an easy to remember “locate” command. Issuing the command followed by a space and the filename returns a list of location where the file could be located. It’s usually required to have root privileged to run the “locate” command. Sometimes though the command returns an error message: locate: can not open ‘/var/lib/mlocate/mlocate.db’: No such file or directory.

The common reason for this error is that the database which locate command uses to store the list of file locations was not yet updated. It’s important to issue the “updatedb” command without any parameters with root privilege. Failure to run the “updatedb” command before using “locate” command will result the error locate: can not open ‘/var/lib/mlocate/mlocate.db’: No such file or directory.

Debugging of Oracle ERP Applications are dangerous to do on production servers. Thus, Oracle testing environments are pretty important for system administrator work. A separate clone Oracle database server with Oracle ERP Application running is a must for worry free debugging and testing. At work RedHat Enterprise Linux kernel version 2.4.9-e.62 host both the Oracle Database and Oracle ERP Application. Recently, we’ve copied the Oracle database and ERP Application from a Linux box to a virtual container for testing.

The copy process using rsync went smooth. We’re confident that everything would work perfectly fine as it’s a clone of the production system. After changing some basic things like hostname, listener.ora and tnsnames.ora file; I was surprised to encounter the message Oracle TNS-12541: TNS:no listener and TNS-12560: TNS:protocol adapter error when running the listener. TNSPING returns also the no listener error.

I am pretty sure to cover the basic configuration and to make things complicated is the Linux Error: 111: Connection refused. I did several check on hostname, iptables and other related stuff, but could not find the solution. Comparing the files between production and clone have shown the problem. The cause is not even close with network connectivity, but with Oracle failing to create temporary files.

In the cloning process the copying of Linux /var/ folder was skipped as the system usually recreates the entries during start. Well, anyway, the error was traced to the missing Oracle temporary file folder /var/tmp/.Oracle. I am not sure what is the connection here, but creating the /var/tmp/.Oracle folder with the Oracle system user right have solved the issue of TNS-12541: TNS:no listener and TNS-12560: TNS:protocol adapter error.

The good thing about virtual machine is that you could change the memory size or the disk space if necessary. I used VMware virtualization software which comes with a tool vmware-vdiskmanager disk expansion software. I delved into increasing the virtual machine disk space, as everything looks straightforward and easy.

I made a backup copy of the virtual disk for insurance. Increasing the disk size was cool. No sweat, but it was not recognized by the system. There are instructions on how to use the extra partition to be part of the main system partition with disk expansion. I followed the outlined task. Surprise !!! Windows XP was unable to boot, screen turns blue and restarts the virtual machine automatically after a few seconds.

The good thing is I made a backup copy, before I DELETED the virtual disk (which is a really dumb thing to do). I copied back the virtual disk backup copy into the same location. Everything worked fine with Windows XP starting up, but the backup copy of the virtual disk seems to be old. I noticed, some latest installation and setup of important software are not there anymore.

The process which started with increasing virtual machines disk size ends up as disaster recovery problem. There’s no guarantee that everything will work fine when it comes to this kind of computer operation. So, I tried to recover the over written virtual disk file with the use of open source TestDisk Photo Recovery Software. I was not lucky with it. So, maybe I’ll try it with the use of commercial file recovery software like Active Undelete.

The result default configuration file entries are based on the data provided on the Network Configuration stage during Linux installation.

Installation Network Configuration data:
Hostname: rhel4ora10g.yes.net
IP: 213.59.28.252
Mask: 255.255.255.0
Gateway: 213.59.28.254
Primary DNS: 213.59.0.1
Secondary DNS: 213.59.63.6

There are three related network configuration files that needs to be checked when installing Oracle Database 10g: a)network, b)hosts, and c)resolv.conf.

/etc/sysconfig/network
NETWORKING=yes
HOSTNAME=rhel4ora10g.yes.net
GATEWAY=213.59.28.154

/etc/hosts
127.0.0.1 rhel4ora10g.yes.net rhel4ora10g localhost.localdomain localhost

/etc/resolv.conf
search yes.net
nameserver 213.59.0.1
nameserver 213.59.63.6

A favorite Linux text editor like “vi” with proper privilege is needed to edit those system network configuration files.

For example, Oracle Database 10g installation requires addition of the following on the resolv.conf file:
options attempts:5
options timeout:15

The files are a good reminder to look back as reference in the future when trouble shooting network problems.

They might be right at some point. Imagine working with the ERP system of the whole institute which hosts Oracle Database and E-Business Suite financial module. Someone has to fill the gap immediately. So, I took the job.

The primary t to do is to have a good backup of the Linux Server. A complete backup could only be done during off office hours where nobody is using the system. Making a scheduled backup data backup is a first thing which needs to be done.

In Linux operating system the time-based job scheduler is known as cron. Crontab is a configuration file that contains shell commands to run on a given schedule. Setting up the crontab is easy with the following command:

$sudo crontab -e

It would prompt for a password then the default text editor will automatically open the crontab file.

Sample content of a crontab file:
59 02 * * sat sh /data/backup10g.sh
59 02 * * tue sh /data/backup10g.sh
59 02 * * wed sh /data/backup10g.sh
59 02 * * thu sh /data/backup10g.sh
59 02 * * fri sh /data/backup10g.sh

The above will run the shell script backup10g.sh which do data backup of the Oracle Database at 2:59 am at any day and any month of the year on particular days of the week.

We know that MySQL open source database has provided end users with a way to avoid expensive database management system license and maintenance fees. It has been a growing database alternative to commercial database systems like Oracle. The number of web applications running on MySQL database is ever increasing. Web hosting services have been offering MySQL database as a standard choice together with PHP application. Also, web application programmers have been comfortable using it in development of web applications. There is even a MySQL cluster offering which is a direct clash with Oracle database. Thus, many viewed MySQL database as a real threat to Oracle.

It’s interesting to know what will happen next to MySQL open source database. Oracle seems to cleverly take out its No. 1 threat by buying Sun Microsystems. I can see that MySQL is in danger with Oracle and Sun deal completed. If there’s an alternative open source patrons would surely choose to avoid Oracle if they can. In the future most likely people will exit MySQL or MySQL will be forked. Or maybe Oracle will put some new technology with MySQL? It’s something to watch out.

Expecting for an Oracle GUI for a Universal Installer, I was prompted by a series of text. It’s good to read closely those text when installing software. The error goes as follows:

$ Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified
Exception in thread "main" java.lang.InternalError: Cant' connect to X11 window server using ':0.0' as the value of the DISPLAY variable.

The detailed error text goes a long way.

The error is basically about the DISPLAY which was not set properly for “oracle” user. Thus, correcting error requires adding the user “oracle” for local access to the display. To correct the error run the following command as “root” user:

$xhost local:oracle

The oracle user then way able to run the GUI of the Oracle Database 10g Installation without being prompted by Xlib: connection to “:0.0” refused by server error.

I tried to verify if ifconfig is really missing. Ifconfig as I know is a built-in Linux system command. I check under the /sbin/ folder and it’s present. Thus, the command could not be found, might be caused by the lack of privilege to run the command.

I login as root user and try to run ifconfig to check the IP address surely everything went okay.

The ntpdate update error is “Operation not permitted”. Aside from that another error showed “No server suitable for synchronization found”. I was puzzled because PING command could reach the NTP server, without any problem.

A closer look revealed that port 123 which is used by ntpdate is being blocked. Opening port 123 within the IP tables solved the “Operation not permitted” error and “no server suitable for synchronization found” error. This kind of solution worked well, but I would like to hear other solution to a similar problem in Linux servers.

The date and time stamps when transactions are done are very significant. I have encountered some cases where the uploaded file date and time stamp on the database does not match with the actual file uploaded on the file server. This creates confusion. Thus, synchronization of date and time from a single standard time server source for every networked computer server is important.

Most of the servers we have are Linux box and ntpdate is the command used to synchronize time with a Network Time Protocol server.

Updating date and time from a remote server is simple using the ntpdate command.

The ntpdate command to update is as follows:

$ntpdate -u 1.th.pool.ntp.org

where 1.th.pool.ntp.org is the remote ntp server and the option -u is for update.

You could read more about ntpdate from the following:

http://en.wikipedia.org/wiki/Ntpdate

Robot computer applications that will run with GNU/Linux is now available. Robot hobbyists, makers, or software developers could now use the Linux-friendly USB-based sensing and control modules from Phidget. Phidget previous product versions need to be connected to a desktop computer via USB to work, but now it released a single board computer (SBC) to work with its other modules.

The Phidget SBC uses a Samsung SC32410 processor that is clocked at 266MHz. The board comes with 64MB of RAM, 64MB of flash storage, and 10/100 Ethernet port. It also has four full-speed USB ports for connectivity with other USB-only Phidget modules. WiFi with webcams could allow remote controlled robotic system.

Designing a robotic system that is driven hydraulically, electrically, pneumatically or even with spring plungers usually needs a programmable controller computer which Phidget SBC could offer. The Linux based single board computer could be the light weight and expandable robotic system controller for home projects and industrial use.

Problems like managing data synchronization and application integration are some of the common things faced by IT support unit. Service Oriented Architecture (SOA) which is a standards-based approach is a thing which we eye to facilitate specialized applications working together.

We’ve got a diverse set of database like Oracle, MSSQL, MySQL, and Postgre which is having front end applications like Oracle Forms and Reports, PL/SQL web applications, PHP web applications, and others. Our IT Unit is thinking of complete process-level integration solution with minimal effort, but we’re on a wall on how to implement this SOA.

Cost on license fees and proprietary software is a major hurdle. Any open source solution would be worth looking into. The ultimate goal is to improve reusability of software assets. Another would be to provide better business and IT integration. All of these will increase response to business changes and demands in the marketplace.

Open source SOA would be a solution for budget tight organizations that like to integrate applications and business processes. I am still looking on learning open source SOA and how to implement it in our institute.

I remember “lynx” as a text based browser for Linux, but it seems not installed in Ubuntu Server 9.04. I tried to use “wget” to authenticate, but still could not access the Internet. Well, to my relief, I found that Ubuntu have a different default browser; it’s called “w3m”. Using it is pretty simple. Just type w3m followed by the URL to be opened.

Sample usage of w3m web browser:
user@techxplore:~$ w3m www.google.com

Developers don’t lack the choices available when building web applications. There are many different architectures, frameworks, platforms, and approach that web developer faces. We’ve been working with PL/SQL Programming Language and Oracle Database for some time already, but recent trends kept us reviewing the long term approach. Rising cost of software licenses and shortage of skilled programmers are some factors that make us rethink moving toward open source solution.

Java Programming with Oracle JDeveloper and Oracle Application Development Framework (Oracle ADF) was considered. Another was Oracle database and the Microsoft .NET platform to create web applications. However, due to the available resources and time constraints we have; we’ve finally settled with PHP coupled with Oracle Database for web application development.

There could be better web application development strategy, but in our case, we’ve matched the availability of skilled programmer with our IT resources. In the end, whatever is the tool used, application developers still need to connect users to information with web applications.

I am very amazed with the particular development of the browser that supports the latest standards. Mozilla’s FireFox 3.5 release is a web browser super charges browsing to the next level. The new release brings speed, security and most advanced Firefox yet.

Download Free Fastest FireFox 3.5 Web Browser:

http://www.mozilla.com/products/download.html?product=firefox-3.5&os=win&lang=en-US

FireFox 3.5 is twice faster the FireFox 3.0 and you’ll never regret downloading it.

The conference show cased a new tool for communication and collaboration on the web, coined as Google Wave. I have watch the demo video of Google Wave on the following link: http://wave.google.com/. The strength of HTML 5 has been shown off as a platform for web application development of real world functional applications. Not only is HTML 5 then for testing. You could sign up also to get updates about Google Wave and how to develop applications around it.

Google Wave web communication and collaboration tool has put upfront the strengths of the upcoming HTML 5 standard for acceptability on web applications development. It’s an eye opener for everyone on the industry.