Hard disk being one of the vital components in computer system. Unfortunately, hard disk is also being one of the most high risk and sensitive components that is prone to failures, owed to the fact of mechanical subsystem attached!
The Linux command badblocks could be used to run bad sector burn-in test on a new or suspected faulty hard disk. Just get a low end PC or server installed with Linux OS, attach the target hard disk to the IDE or SCSI bus, and run the badblocks command on the target hard disk. For example,
badblocks -svw -t random -p 3 /dev/sdb
get badblocks to perform three rounds of destructive write of random data to the second SCSI hard disk.
Be careful! The option switch -w performs destructive write. Never use this option switch on a partition with filesystem. Instead, use -n to perform non-destructive read-write on a partition with filesystem!
Sunday, October 15, 2006
Hard disk being one of the vital components in computer system. Unfortunately, hard disk is also being one of the most high risk and sensitive components that is prone to failures, owed to the fact of mechanical subsystem attached!
DBA suggests few of the recommended database performance tuning tips for IBM DB2 database engine that is running on Linux server.
Executing command sysctl -A to print out current kernel parameters setting. Some of the notable are
In order to retain these changes of kernel parameters on every system reboot, add the updated kernel parameters setting to /etc/sysctl.conf system file to do the great job.
Recommended Value : 250 256000 32 1024
Recommended Value : 1024
Recommended Value : 65536
Recommended Value : 65536
After connecting to database called my_test_db by executing db2 connect to my_test_db, running another DB2 command db2 autoconfigure apply none to get DB2 database engine calculate the best recommended value of DB2 database configurable parameters. Some of the notable are
Larger log buffer required for OLTP workloads with high transaction rate.
For databases with heavy update transaction workloads, make sure there are enough clean pages in the buffer pool by setting the parameter value equal to or less than the best recommended value calculated by DB2 database engine.
The amount of storage that is allocated to the lock list. Increase this value if lock escalations causing performance concerns, that logged as warnings in the db2diag.log file.
Database heap per database. Needs to be increased for larger buffer pools.
Large buffer pools require a higher number of asynchronous page cleaners.
DB2 UDB ESE v8.2 introduces a new buffer pool page cleaning algorithm which is not turned on by default. It is necessary to test this new page cleaning algorithm with the database workload. To turn on this alternate page cleaning algorithm, executing DB2 command
Don't ever press CTRL+ALT+DEL key combination in a Linux server!
Windows guys used to press CTRL+ALT+DEL key combination follow by ENTER key to immediately lock the server running on Windows 2000 or Windows XP and above when they leave the server.
What is the default behaviour when pressing CTRL+ALT+DEL key combination in a Linux machine? Well, the default action of Linux in responding to CTRL+ALT+DEL key combination is to reboot the Linux machine immediately! Just press it once, not twice as in Windows Me, and Linux will not be kind to ask confirmation before it really rebooting itself!
Anyway, this Linux default behaviour in responding to CTRL+ALT+DEL key combination pressed could be tweaked, indeed. Edit the /etc/inittab system file, look for the line containing ctrlaltdel keyword, and then either
dialog --clear --title "Information" --msgbox "Don't press CTRL+ALT+DEL key combination in Linux machine.\n\nTo reboot server, use init 6 or init 0 to shutdown Linux." 10 40;clear
which use the dialog box command to alert users with a text-based GUI information dialog box.
Opss! Executing ls command at keith login account displaying directories in blue color, executable file in green color, and plain text file in white color, etc.
But, when executing the same simple ls command at root login account does not differentiate file type by color scheme. How come?
Users who are familiar with shell built-in command alias will know that it is the alias that wrap the ls command with --color=none option switch. At the command prompt, type
alias | grep ls
will able to tell the fact of this.
The which command is used to find out which command the Linux shell interpreter is referring to in the current login session. The simple form of which command, such as which ls will show the path of the ls command without telling the alias name of it. Well, tweak which command with its command option switch and wrap it with alias command, such as this
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
Execute the which ls again, will now able to show both the ls command path and the alias of it, as shown in the diagram.
Tired of typing Linux command because of long list of command option switches? Try to use the command alias to relieve tired of typing long Linux command then.
As the command name suggests, the Linux shell built-in command alias allows a user-defined command to represent
find . -type d -print
This find command used with a long option switches to list all directories that exists from the current directory downwards. The find command could be rather long if more find command option switches applied.
This long command line could be made simple with an alias, such as
alias dirfind='find . -type d -print'
that allows user to execute the short user-defined command dirfind instead of typing out that long command line.
tar -zcvpf bin.tgz bin; [ $? -eq 0 ] && echo DONE || echo FAIL
These system commands execute sequentially, aim to check the tarball archive creation status upon its completion. If success then echo DONE else echo FAIL.
Again, by using the alias command could make it shorter and simple enough, such as
alias chkbkp='tar -zcvpf bin.tgz bin; [ $? -eq 0 ] && echo DONE || echo FAIL'
where the user could execute chkbkp at command prompt and the Linux shell will expanding it to that commands series.
To run a shell scripts in current shell environment instead of spawning into subshell, use one of these two syntax
Saturday, October 14, 2006
Bootp, shorts for Bootstrap Protocol, is an UDP network protocol which is originally defined in RFC 951 to assign IP address for network clients. Bootp is well suitable to apply in diskless workstation, workstation without operating system installed, or simply called thin client.
Bootp is not DHCP! Although both of these two protocols sound similar at first thought, but they are technically different and could be co-exists in the same server or network segment.
Hospitality management system giant, Micros System Inc, makes good use of bootp in its high rank Point-Of-Sale system called Micros 8700 HMS.Bootpd server and clients could be reside on different network segment by deploying bootp relay agent. To make thing simple or get it up and running right during initial roll out, put both bootpd server and client on the same network segment.
When the diskless Micros PC Workstation power on, the bootp enabled network interface card will broadcast its MAC address to the network. When the bootp daemon running on the Micros host receives the broadcast packets, it will assign a valid IP address follow by transferring a DOS operating system image to the PC Workstation according to the MAC-IP-Image mapping maintained in the bootpd configuration file.
Once the image transferring (via tftp protocol) completed, the diskless PC Workstation starts to boot up with the OS image parking in memory segment that act as RAM-DISK. When the boot up completed, the Micros diskless PC workstation functions as if it is a normal desktop PC pre-installed with DOS OS.
Checklist when thin client unable getting IP address:
ps -ef | grep bootpd
lsof -i | grep 67
to confirm bootp daemon is running and listening to legacy port number (as shown in /etc/services file)
to list the bootpd server arp cache. Confirm that there is no ARP cache conflict. To delete the conflict, for example conflict on IP address 192.168.1.3, execute command
arp -d 192.168.1.3
Thursday, October 12, 2006
PST, known as Microsoft Outlook personal folder file or email archive file, used to archive emails out from the mail box at server side to a local storage or network drive.
OST, known as Microsoft Outlook offline folder file, allows user to work with Microsoft Exchange mail box in an offline mode. For example, emails composed, Contacts or Calendar changes, etc, will be storing in the offline folder. These changes made in offline folder will be automatically synchronize with Microsoft Exchange Server once hook up to the network - emails composed will be sending out immediately and Contacts or Calendar changes are updated to server side objects.
Both the Microsoft Outlook PST and OST files are believed using MSDE database engine.Watch the size of PST and OST file! If they getting fatty, trim them down quickly to save archives of email from hitting the 2GB limitation or a file corruption will happened soon! The best practice is to create multiple PST or OST files to categorize email archives. For those email with attachment, it is easily reaching the 2GB limitation. So, more PST or OST files are needed to archive such emails with attachment!
MSDE is a light-weight freeware version of Microsoft SQL Server database engine that Microsoft offers to attract database users (especially MS Access users, developers, students, educators, etc) to develop database projects using Microsoft SQL Server. The latest release of MSDE is called SQL Server Express edition.
MSDE built with limitation of accessing up to 2GB worth of data only. The same limitation occurs in MS Outlook PST and OST file as well!
Office 2000 and higher with latest patches installed is nice enough to alert users with an error message and disallow users from adding or receiving new email item, so to safeguard PST or OST file to become oversize and corrupted. Earlier versions of MS Outlook does not display any error or warning messages and allow users to oversize the PST or OST file until corruption!
Microsoft offers a tool called PST2GB to recover a MS Outlook PST file that is corrupted after storing over 2GB worth of data. Microsoft alleged that PST2GB is not a tool that is 100% work at all time! If PST2GB does work, it does not recover all of the data (the truncated data is missing).
PST2GB merely create a truncated copy of the PST file to under 2GB. The copy that is left after the PST2GB completes does not have all the original data because the PST2GB forcibly cuts a user defined amount of data (below 2GB) from the PST file.Steps to recover corrupted PST file as per Microsoft KB296088 (applied to MS Outlook 97 to MS Outlook 2002)
If the following error message arise when trying to run the PST2GB Utility
Run-time Error '713': Class not Registered. You need the following file to be installed on your machine. MSSTDFMT.DLL
To resolve this error, follow these steps:
where <windir> is either the WINNT or the Windows directory.
Wednesday, October 11, 2006
Samba server comes with a handy utility called smbstatus to report users who are holding the shared resources.
Utilities used to find out processes that are locking system resources are among the most wanted system utilities for experienced users and system administrators. The lsof being one of such excellent utility that used to identify process or user that is locking system resource such as file or network socket.
For example, a system administrator could use the lsof -i to easily understand how the IBM MQ server communicate over the TCP/IP network with IBM Informix server. The lsof output, as in the diagram below, shows that the Informix oninit is listening to a user defined mnemonic port name stp which the IBM MQ server communicate with. The /etc/services system files is usually used to map a numeric port number to a descriptive port name defined by user.
Each of the process id suffix with an ASCII character code which represent the resource access type. These resource access type codes are not standardize among various Linux distributions. To be safe and accurate, always consult the fuser man page to confirm the code definitions.
To check out what process ID is using TCP port 8080, execute the fuser as fuser -n tcp 8080 or fuser 8080/tcp
will shows both the program and process id that bind to the network port. The diagram below shows the commands output of lsof vs netstat.
Both of the commands displaying pseudo port name instead of numeric port number, where the mapping of pseudo port name and numeric port number is defined in /etc/services file.
The netstat command, however, able to display numeric port and IP address with -n option switch. For example, rewrite the command as netstat -tulapn
Note! Both netstat -tulap and lsof -i MUST be executed with root user account privileges, else nothing as those in the diagram above will be seen.
Tuesday, October 10, 2006
Boot up to Windows Recovery Console and execute command bootcfg to repair corrupted or recreate missing Windows boot.ini file.
The bootcfg command able to scan hard disks for installation of Windows NT 4.0 and above and then add them to existing boot.ini file. The command also able to rebuild a new boot.ini file if one does not exist.
A brief of bootcfg command usage and syntax
Windows Me or 9x comes with one handy network chatting program called Winpopup. Simple GUI allows user at one computer to chat over the network with counterparts sitting at another networked Windows.
However, there is not similar Winpopup replacement for Windows 2000 and above. There are two ways to send a message, better known as console message or Windows Alerts, to networked system running Windows 2000 and above.
net send 192.168.1.2 "testing messages"
to send a messages "testing messages" to PC with 192.168.1.2 IP address.
It is possible to replace IP address with DNS name or domain name to send console message to all workstations of the said domain.
Opsss! Can't VNC over to remote hosts!
Might need to restart the VNC server, but how?
netstat -ant | grep 5901
where 5901 is the legacy VNC daemon listening port of DISPLAY:1 in the previous step. If the port is open and listening means that VNC daemon is up and running successfully.
The shell scripts wrap the default md5sum program found on most Linux system to prepare a report of unique and duplicate files in a given directory.
The lengthy source code could be shorten if removing the DupUniRpt function which merely used to prepare an easy to read report that showing both the filename and number of duplicate and unique files.
By removing the DupUniRpt function call and function coding, do remember to add the line
right after the DupUniRpt function call in the if-else statement. The $FM5L is a semi-raw report file that groups duplicate and unique files together.
The wDupUniRpt.sh contain the same source code of DupUniRpt function source code, which could be used to prepare that easy to read report based on the semi-raw report file. This shell scripts created merely for easy debugging purpose.
Both these shell scripts have been tested successfully with as much as possible scenarios. The source code might be able to further enhanced for efficiency or bugs fixing if any. Any suggestive comments are greatly appreciated.
Monday, October 09, 2006
Recover Console is not install to local hard disk by default during Windows installation.
In order to access to Recovery Console, normally practice is to boot up the system from the appropriate Windows setup CD. If the system is running on Windows XP, use the Windows XP setup CD. Note that Recover Console only available in Windows 2000 and above.
Other than access the Windows Recovery Console from bootable Windows setup CD, it is possible to install the Windows Recovery Console to local hard disk and configure it to appear as one of the Windows boot up option.
Install Recovery Console to local hard disk and enable Recovery Console as part of the Windows boot up menu option:
C:\cmdcons\bootsect.dat="Recovery Console" /cmdcons
Note that changing the description "Recovery Console" to whatever meaningful name is possible.
The ls command is a Linux command that is used to list directory contents. In fact, it is a standard shell command that exists in all Unix/Linux variants.
Using ls command by examples
- To list all files in ascending order of file name detailed with file modification time
- To list all files in descending order of file creation time in full or customized date-time format
ls -lact --full-time
ls -lact --time-style="+%d %m %Y"
- To list all files in descending order of file creation time
- To list all files in descending order of file size in kilobytes
- To list only directories
ls -ap | grep /
ls -al | grep ^d
Alternatively, use the find command as
find . -type d -print
- To list only directories initial with rpt filename
ls -al rpt* | grep :$
find . -type d -name "rpt*" -print
- option switch l used to list files in long listing detailed format.
- option switch a used to list all files including hidden files which filename prefix with a dot.
- option switch lct used together to list file in descending order of file creation time.
option switch lc list file creation time and sorted by filename.
option switch lt list file in descending order of file modification time.
- option switch h used to list files size information in kilobytes (KB).
- option switch S used to list files in descending order of file size in byte.
- option switch r used to reverse the default of descending listing order to ascending listing order.
- option switch --full-time or --time-style used to display time-related info in full or customized format.
- On ad-hoc basis by adding option switch. For example
ls /etc --color=none
to list /etc directory contents without color scheme turning on. OR
- On selective login session only. Use the alias command to save typing efforts. For example, execute the command
alias ls="ls --color=none"
will cause subsequent ls command executing as if it is supplied with --color=none option switch and automatically turn off the color scheme.
- On each login session of individual login acount only. Copy the file /etc/DIR_COLORS to the user home directory as $HOME/.dir_colors and edit the variable COLOR to become COLOR=none to do the job.
From the next user login onwards, type the command set | grep COLOR will notice that the COLORS variable changed as specified in the $HOME/.dir_colors setting file. Typing the ls command as usual which will disable the file listing color scheme automatically.
To turn on the color scheme again, simply rewrite the line COLOR=none to COLOR=tty or COLOR=auto will do.
The file /etc/DIR_COLORS is used to control file listing color scheme globally, meaning that all users account will be affected.
Friday, October 06, 2006
Yes! Effective 19 April 2006, all Visual Studio 2005 Express Editions are free permanently!
Microsoft Express Edition includes a wide range of Microsoft flagship development tools such as MS SQL Server 2005, Visual Basic 2005, Visual C# 2005, Visual C++ 2005, Visual J# 2005, Visual Web Developer 2005. As long as Express keyword attached, such as Visual Studio 2005 Express Editions, it is a genuine Microsoft freeware edition.
For those who familiar with MSDE, SQL Server Express is the replacement. Microsoft alleged that the name MSDE was confusing to customers and partners because many did not realize that it was associated with SQL Server. By changing the name from MSDE to SQL Server Express there will be less confusion among customers and partners.
Everyone could use the Expression edition at no cost for the purpose of testing, learning, and even compile and sell the development project. Before this, Microsoft freeware such as Visual Basic Learning edition couldn't compile development into executable.
Tuesday, October 03, 2006
By convention, Windows system using 3 alphanumeric characters to serve as file extension. File extension telling Windows OS how to deal with the file, what program to manipulate the file, and to Windows users easily recognize a common file type.
There is no such strong concept of file extension in Linux as well as UNIX world. Linux folks, however, do practice to use file extension for some file formats such as compression or archive file format. Windows users might easily get cheated by file extension trap in Linux.
For example, it is perfectly fine to rename a PKZIP compatible zip file called backup.zip to backup.tgz or whatever filename. Later, if the user simply executing tar -zxvf backup.tgz might either get errors or see nothing and thought the file is corrupted.
Wait! Before deleting the file which thought to be corrupted, use the file command to inspect the file type first.
Type file backup.tgz at the command prompt, it shows that backup.tgz is actually a PKZIP compatible zip file. So, user should executing unzip backup.tgz to extract the zip file or rename backup.tgz to backup.zip before executing the unzip command.
Tuesday, September 26, 2006
Starting Redhat 7.3, Redhat Linux support two type of printing system known. These two subsystem are known as LPRng and CUPS respectively.
While at command prompt, executing printconf-tui (Redhat 7.3) or redhat-config-printer-tui (Redhat 8.0) to bring up command line version of LPRng printing manager.
For the graphical version, click on the Main Menu => System Settings => Printing or type redhat-config-printer or printconf-gui at a XTerm or Gnome terminal shell prompt to bring up the same GUI program.
To allow only a few selected users to use a printer called inkjet-graphic, execute the command lpadmin -p inkjet-graphic -u allow:keith,jazz,alice and these setting will be updated to /etc/cups/printers.conf configuration file.
Note! The printer manager utility, printconf or lpadmin, saves any printer configurations made to the /etc/printcap setting file. If there is a need to make any printer configurations outside the printer manager utility, add them to the /etc/printcap.local file. The /etc/printcap file will be deleted whenever the printer manager executing or a server reboot.Steps to add new printer is almost the same among printer manager utilities. In brief, these are the key points to get it works:
To enable local printer sharing for remote host:
Monday, September 25, 2006
Redhat Enterprise Linux device file permission could not be changed simply by using the chmod command. Instead, the device file permission is set by udev hotplug subsystem which is included in almost every 2.6 kernel based Linux distribution that is shipping.
The configuration file /etc/udev/permissions.d/50-udev.permissions defines the permission of each devices present in the Linux system. For example,
The default permission defined is 0660. Simply change the 4 digits code as usual to an expected permission, say 0666 instead of 0660.
Nagios is the answer!
It is licensed under the terms of the GNU General Public License Version 2 as published by the Free Software Foundation.
Nagios is a powerful system and network monitoring application. It monitors hosts and services specified, alerting administrators when threshold triggered, and when they recover to healthy state.
Nagios is only available in Linux or UNIX variants. Although, it could helps to monitor Windows servers as well via the Windows version of Nagios client.
FTP is a legacy file transfer protocol that has been widely used since the day of networked computing.
Other than using the serious typing of command line FTP client, such as the standard FTP client offers by all Windows system, Internet Explorer able to serve as GUI FTP browser too!
Follow these simple steps to turn IE into a graphical FTP client:
Saturday, September 23, 2006
The Windows Recovery Console is designed to help system administrators recover Windows-based computer that fails to start up properly. It is available only in command prompt. Hence the name "Console" attached. It looks like the Windows 9x boot disk, but Windows Recovery Console is more powerful and features rich than the old Windows boot disk.
Basically, Windows Recovery Console allow system administrators to:
By default setup, Windows Recovery Console with Administrator account logon allows access to only
Trying access to folders other than those listed above will rejected with an "Access Denied" error message. Besides that, Windows Recovery Console disallow copy files from local hard disk to removable storage such as floppy disk. However, Windows Recovery Console allow copy files from removable storage to local hard disk or copy files from one hard disk to another hard disk.
Although, limitations imposed on default setup that stated above could be resolved by
Note! As a security measures, it might be wise to double-click on "Recovery Console: Allow automatic administrative logon" policy too and disable it.
Friday, September 22, 2006
Nothing special. Just a simple shell scripts, could be served as an introduction of Unix Shell scripts programming, written to check disk space utilization of Linux (applicable to Unix too) filesystems or partitions.
Note! Ignore the left most numeric digits which are not part of the Shell scripts coding. These are line number indicators, which could be turned on in Vi editor using the :set nu command code.
It might be useful to comment out line 14th and remove the hash key on line 15th, which disable echo alert to console and enable alerts emailed to mail box. Configure Linux scheduler via the crontab -e to run this shell scripts, perhaps once a day, and get system administrators alarmed of critical free disk space before the system comes to halt.
Tuesday, September 19, 2006
What could be done besides rebooting Windows server when a particular Windows service become unavailable to start, stop, pause, resume, or restart?
Restarting a Windows service, particular a poorly coded third party Windows service, may turns out to become unable to start, stop, pause, resume, or restart, after the service timeout and fail to startup successfully again. All these five common actions or tasks are dimmed and become unavailable. Restart the Windows server is not the only way, and might not advisable too, to resolve the problem.
Try this before deciding to reboot the Windows server:
These optimization tips are suggested by Nagios official documentation. It might be useful to fine tune Nagios for optimum performance and effective monitoring service.
In order to compile in the embedded Perl interpreter, set the --enable-embedded-perl option in the configuration script before compiling Nagios. In addition, use the --with-perlcache option to enable embedded interpreter caching the compiled Perl scripts for later reuse.
Hence, it would be much faster to set the max_attempts value to 10 and only send out 1 ICMP packet each time, instead of specifying a max_attempts value of 1 in the host definition and having the check_ping plugin send 10 ICMP packets to the host.
However, the pitfalls of this arrangement will happens when the hosts are slow to respond may be assumed to be down. Another option would be to use a faster plugin check_fping as the host_check_command instead of check_ping.
Note! Many Linux installations do not attempt to optimize IDE disk access. Use hdparam to change the IDE hard disk access parameters to gain speedy features of the new IDE drives.
Sunday, September 17, 2006
LargeSystemCache determines whether Windows 2000 Server should maintains a standard size or a large size file system cache, and influences how often the system writes changed pages back to hard disk.
Increasing the size of the file system cache generally improves server performance, but it reduces physical memory space available to applications and services. In addition, writing system data less frequently minimizes use of the kernel disk subsystem, but the changed pages occupy memory that might otherwise be used by applications.
LargeSystemCache is DWORD registry data type that could be located at registry path
HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management
Setting LargeSystemCache to 1 (system default)
Establishes a large system cache working set that can expand to physical memory, minus 4 MB, if needed. The system allows changed pages to remain in physical memory until the number of available pages drops to approximately 250. This setting is recommended for most computers running Windows 2000 Server as file server on large networks.
Setting LargeSystemCache to 0
Establishes a standard size file system cache of approximately 8 MB. The system allows changed pages to remain in physical memory until the number of available pages drops to approximately 1,000. This setting is recommended for servers running applications that do their own memory caching, such as Microsoft SQL Server, and for applications that perform best with ample memory, such as Internet Information Services web server.
Other than access to registry via regedit.exe and edit directly, alternative method to tweak LargeSystemCache is by
The default setup of Windows 2000 Server initialize LargeSystemCache to 1 which is ideal when running as file server. However, setting LargeSystemCache to 1 can degrade service performance. As such, it is not appropriate when running as application servers such as Web server, SQL server, Exchange server. In this case, reset LargeSystemCache to 0 by selecting the Maximize Data Throughput For Network Applications option in Network And Dial-up Connections.
Compression ratio depends on data and algorithm used for compression. Compression speed counts on CPU power and data compression algorithm in used. Some compression utilities such as 7za, gzip, bzip2, etc, come with options to set level of compression. Setting to higher level of compression will means more time taking to compress and decompress too!
Follow the links below to the comparison of various file compression formats. Find the best compression scheme that suit better for a particular application.
Excerpt from the source:
lzop is the fastest tool. It finishes about three times faster than gzip but still compresses data almost as much. It finishes about a hundred times faster than lzma and 7za.
Get even higher compression ratios by combining lzma with tar to increase storage space effectively by 400%.
The data compression tool with the best trade-off between speed and compression ratio is rzip. With compression level 0, rzip finishes about 400% faster than gzip and compacts data 70% more. Rzip default compression level is another top performer too as it can increase effective disk space by 375% but in only about a fifth of the time lzma can take.
Rzip accomplishes this feat by using more working memory. Whereas gzip uses only 32KB of working memory during compression, rzip can use up to 900MB! But that's okay since memory is getting cheaper and cheaper.
Thursday, September 14, 2006
7-Zip is a full function file archiver freeware!
7-Zip default to compress files in .7z compression format using LZMA compression algorithm.
LZMA, shorts for Lempel-Ziv-Markov chain-Algorithm, is a data compression algorithm developed on 2001. It uses a dictionary compression scheme similar to LZ77 (such as Gnuzip - better known as gzip in Linux world) but features withBesides supporting 7z compression format, 7-Zip too able to compress and decompress some other popular compression formats.
- high compression ratio
- variable dictionary size up to 4GB
- compressing speed at about 1MB/s and decompressing speed at about 10-20MB/s on 2GHz CPU
- little memory require for decompressing depends on dictionary size
- small code size for decompressing at about 5KB
- supporting multi-threading and Intel Pentium 4 HT technology
- Supported compression file formats:
7Z, ZIP, GZIP, BZIP2 and TAR
- Unzip compressed file formats:
7Z, ZIP, GZIP, BZIP2, TAR, RAR, CAB, ISO, ARJ, LZH, CHM, Z, CPIO, RPM, DEB, and NSIS
Others attractive features of 7-Zip such as:
- Supports files size up to 16000000000GB
- Unicode file name
- Self-extracting capability for 7z format
- Integration with Windows Shell
- Ability of using any compression, conversion or encryption method
- Multilingual interface up to 63 languages at time of writing.
- Available in various platforms such as both Windows 32-bit and 64-bit version, Unix, FreeBSD, Redhat, Fedore Core, Debian, Gentoo, Mac OS X, BeOS etc
Tweaking Windows core performance by editing registry key called DisablePagingExecutive only if
- plenty of memory installed, e.g. 1 GB RAM or more
- most of the memory being unused or idle on most of the time (wasting resource!), and
- Windows 2000 and above (Windows XP, Windows 2003) is running.
HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management
The initial setup of Windows XP default DisablePagingExecutive value to zero. Setting this value to 1 to enable Windows core to fully utilize the huge memory installed. Tweaking this registry key benefits driver debugging too as all of the code and data are always memory resident. It also improves Windows system core performance by preventing high frequency of disk read in order to get code and data out from hard disk to memory for processing!
- Search more related info with Google Search engine built-in
Wednesday, September 13, 2006
When the hard disk space going larger and larger, more files are storing into it. Over the time, there might be a lot of duplicate files scatter around the file system.
As bulk of these redundant files are here and there, redundant files mess up file system, decrease system performance, wasting valuable disk spaces, and ineffective file backup. It takes time and could be a really tedious job to find and delete these redundant files when low disk space alarmed!
MD5 checksum could be a good candidate to find duplicate and redundant files! It could be used to precisely identify which files have updated since last backup done by comparing the MD5 checksum of files between source and target of the backup.
MD5 short for Message-Digest algorithm 5, is a widely-used cryptographic hash function with a 128-bit hash value. MD5 has been employed in a wide variety of security applications used to check the integrity of data stream, TCP/IP packets, files, etc.Related information:
Tuesday, September 12, 2006
ExtractNow is a great non-adware freeware used to decompress RAR compression file format!
As its name suggests, ExtractNow is merely an decompressing utility and is not a complete archival software. Nevertheless, this simple free utility is more than enough to satisfy today most decompressing functions. Other than supporting RAR compression file format, ExtractNow also support today majority compression file format such as ZIP, ISO, BIN, IMG, IMA, IMZ, 7Z, ACE, JAR, GZ, LZH, LHA, and SIT!
ExtractNow developer suggest not to bundle DLL that used to enable SIT compression file format support in its installer so as to reduce (installer) file size. Having say that, separate download of DLL is needed if expected to enable SIT support in ExtractNow.Related information:
Sunday, September 10, 2006
Email a big file of few megabytes as attachment is never a good idea as it will likely to hang up the email server. Because of that, most email servers are likely configured to not relay or process email with non friendly attachment too. If it is really need to email such attachment,
CAUTION! It is better to zip the files with strong encryption before uploading to any public file sharing providers. Zip the files with encryption helps to reduce file size as well as protect sensitive data from the eyes of non expected readers!
File splitter is preferable than span disk feature of zip utilities as file split could be rejoined with Windows built-in command whereas "span disk" require the receiving end to have similar zip program installed.
copy /b File.1 + File.2 WholeFile.exe
to rejoin split files called File.1 and File.2 back to its original and workable file called WholeFile.exe
VNC shorts for Virtual Network Computing which is based on Remote Frame Buffer (RFB) protocol. VNC enable any VNC compatible clients running on any platform to access remotely, in graphical mode, to any VNC compatible server running on any platform!
For example, a VNC client running on Windows XP able to remote access to the Redhat Linux X windows via VNC daemon running on Redhat Linux, or the Redhat Linux VNC client able to access to Windows XP and run the Windows program in Windows XP via the VNC session.
The term daemon is normally refers to Linux/Unix-based server application/process. So as here. And the term "server" is then refers to a Windows-based server application/process.VNC provides not only GUI remote access but also persistent desktop where the long running program or unfinished editing works could be kept running while VNC session is closed. User could reconnect back later at some other places and straight away continue to work on the incomplete tasks.
However, there is a different in handling convention VNC session between Linux to Windows and Windows to Linux. When access from Linux VNC client to Windows VNC server, the screen seen in Linux VNC client is the same as one see in front of the real physical GUI console. When a Windows VNC client connects to Linux VNC daemon such as VNC Server, the screen seen in Windows VNC client is different from the real physical GUI console. This happens because the Linux X windows use the default :0 display (X server screen number) on startup and the port is not sharable with other sessions. The work around is by using x11vnc or the Redhat bundled Vino as VNC daemon.
Vino allow legacy VNC client access directly to the :0 display. For example, Redhat Enterprise Linux ES 4 comes with vino RPM package. Once installed, the Vino is called Remote Desktop and normally grouped under Preference menu. Its simple GUI configuration make it easier to startup the Vino's VNC daemon!
VNC Server is bundled with all Redhat Linux distribution. Once installed, start the VNC Server by typing vncserver at command prompt. The vncserver command, is actually a shell scripts file, bring up the first VNC Server daemon listening to TCP port 5801 & 5901 by default. To bring up second VNC Server daemon, specify a port number other than the default. For example, type vncserver :2 to bring second daemon listening to TCP port 5802 & 5902. Port number starting from 5801 is meant for Java-enabled web browser connection, while port number starting from 5901 is meant for legacy VNC client connection. Although VNC Server could not directly connecting to :0 display by default as Vino or x11vnc do, this feature could be enabled by using VNC loadable module for the X Window system or upgrade to VNC Server version 4.x.
x11vnc works like Vino but has much more features bundled such as built-in SSL encryption/authentication, file transfer, etc. x11vnc is written in plain C language and uses only standard libraries. So, there is no compatibility and performance issues by using x11vnc as VNC daemon, indeed!
Connecting from VNC client of any platform to Windows VNC server is quite straightforward. Just type the IP address of the Windows VNC server in VNC client will do. However, a combination of IP address and display port is used to connecting VNC client of any platform to Linux VNC daemon. The display port number is taken from the last 2 digits of Linux VNC daemon listening port number (ignore leading zero if any). For example, type http://10.170.46.111:5801 at any Java-enable web browser in order to connect to a Linux VNC daemon that listening to port 5801 or type 10.170.46.8:1 at any legacy VNC client in order to connect to Linux VNC daemon listening to port 5901.