Walker News » Redhat

Is there A Reliable Cracked Software? Why Use Genuine Software?

Walker — Sun, 24 May 2009 08:53:34 +0000

Why using pirated software?

About 10 years ago, I spent all money on my first DIY computer, but almost zero cost on all Windows software installed onto it.

Obviously, I used pirated program, with installers borrowed from friends or bought them myself from pirated software booth at a flat price of 3 – 5 buck per CD.

Why I did that?

First, I was about to start the 1st semester of computer study in college on my own limited finance. As you may know, the hardware was not cheap at that time, so I couldn’t afford to spent additional on genuine software.

Second, none of the people I knew in college or friends were using Linux or open source software. As a novice at that time, learning Linux on my own could be a great challenge. In order to learn from peer and “masters” around me, I had no choice to go for Windows. Since all of them were using pirated Windows and also my limited finance disallowed me to have genuine software, I just followed the “culture”.

Why using Genuine software now?

Before Windows XP released, most of the pirated software were actually “cracked” by using a genuine product key or serial number.

By using this method, there is no worry of Trojan or virus, so long as you install the software with a genuine installer and activate it with “pirated” product key that is actually a genuine license key shared by millions of people around the world.

However, software activation changes after Microsoft introduced Microsoft Product Activation or Windows Product Activation, started with Windows XP.

Many other software follow the way of Microsoft licensing Windows XP, i.e. to install the software with a valid product key and then activate it within grace period, by connecting to the software vendor server or phone the call center to get an activation key for this purpose.

Therefore, most of the pirated software nowadays are not simply a result of cracking with genuine product key. Indeed, these are really “cracked” software that done by repackaging genuinely installed and activated software, fooling the software with a locally installed activator, etc.

I don’t kinda like these kind of “cracked” software as I am worry about risk of Trojan or virus that might have built into the activator or repackaged installer.

How To Allow Root Login To Telnet Server In Linux?

Walker — Tue, 17 Mar 2009 17:15:23 +0000

Although remote access via telnet protocol is highly discouraged by most system administrators, there are still fans and old boys who are reluctant to change.

Interestingly, these people (who I’ve been dealing with) are all Windows users, i.e. they either use Windows at most of the time or they never have their hands on Linux at all.
So, I guess these people will only abandon telnet client when Microsoft start to bundle Secure Shell (SSH) clients with Windows OS :-(

Now back to topic, if you really want to put the Linux host at risk by allowing telnet protocol, here is the way to enable telnet server in Red Hat Enterprise Linux system (in case you’re asking).

Next, we look at How to enable root account telnet to Red Hat Linux system, if you have nothing to worry about system security (because you’re sysadmin, not security administrator :-)

Telnet client transmit account password in plain text format over (vulnerable) network. Thus, by default, Red Hat Linux (and most Linux distributions, I believe) disables telnet daemon and disallow root user to login directly via telnet protocol.

When you telnet to RHEL server with root ID, it will always rejects with message saying “Login incorrect”, no matter how many times you’ve entered the correct root password:

To overcome this “problem”, simply open /etc/pam.d/remote and remark this following line, where the PAM module pam_securetty.so disallows root user login remotely via telnet and the alike (except SSH).

Original /etc/pam.d/remote with this line:

auth       required   pam_securetty.so

Tweaked /etc/pam.d/remote that remark (comment out) pam_securetty.so:

# auth       required   pam_securetty.so

This guide has been tested successfully on system running RHEL4. It should be valid for use in other Linux distributions that implement Linux-PAM modules (Pluggable Authentication Modules for Linux).

How To Create Volume Group And File System With LVM2 In Linux?

Walker — Sat, 07 Mar 2009 09:43:32 +0000

LVM, shorts for Logical Volume Management, is available in most modern Linux distributions. If I recall correctly, the disk layout for file systems of Red Hat Enterprise Linux 4 default installation is based on Logical Volume Management.

As the name implies, LVM is a software technique to consolidate a group multiple block devices (hard disk or disk partition) and present them to OS as a single disk volume. In other words, system administrator can build or create a 500GB file system with 2 units of 250GB hard disk.

Another advantage of using LVM implementation is flexibility to perform on-the-fly resize for the file system that built on this virtual disk partition, by adding in more physical hard disks and disk partitions.

^{A visualized concept diagram of the Linux Logical Volume Manager or LVM}

How to create a new volume group (VG) and file system on Logical Volume (LV)?

Base on RHEL4 and LVM2 as the platform, here is the summary of steps to build a new volume group (VG), create a Logical Volume (LV), followed by making new file system on it.

As with most Linux commands, the LVM and file system related commands come with number of option switches to extend or overwrite the command default behaviour.

Obviously, this general guide doesn’t cover detail of all option switches. For your own good sake, just vet through the command manual page to see if any of those option switches applicable to your environment.

1) Use lvmdiskscan to find out how many block devices (hard disks or disk partitions) seen by OS are currently used for LVM:

2) With reference to lvmdiskscan output, the /dev/sda2 disk partition is not currently used for LVM. However, it might be used by Red Hat.

So, you’ve to verify or confirm which of the non-LVM block devices are not currently used by Red Hat with the df command. For example, this following df -h output clearly indicates that /dev/sda2 and /dev/sda3 are actually mounted as root and boot file system respectively:

3) Now, let say I decides to create the new Volume Group (VG) with two unused SCSI hard disks, /dev/sdh and /dev/sdi. So, let’s use the pvcreate command to initialize these two SCSI hard disks for use by LVM:

pvcreate /dev/sdh /dev/sdi

The pvcreate command creates the VGDA, shorts of Volume Group Descriptor Area, for LVM to keep track Physical Extent (PE) allocation history, among other things. The initialized hard disk is known as Physical Volume (PV).

The manual page suggests setting a DOS disk partition to Linux LVM partition type (0x8e) prior to execute pvcreate command. But, why not to keep a standard by explicitly creating or changing non-LVM partition to LVM partition type?

1) To change existing, non-LVM disk partition to LVM partition type (0x8e) by using fdisk command:

2) To use the entire hard disk for LVM, simply proceed with fdisk to create one primary partition to take up whole hard disk space and then set the partition type to 0x8e.

The pvcreate manual page, however, suggest a faster approach by destroying the existing partition table, with this dd command:
dd if=/dev/zero of=/dev/sdi bs=512 count=1

4) Now, use vgcreate command to create a new Volume Group called vg7, using the block devices (/dev/sdh and /dev/sdi) initialized by pvcreate command in previous step (you may run pvdisplay to see difference of before and after executing vgcreate command):

vgcreate -s 16M vg7 /dev/sdh /dev/sdi

A Volume Group can be thought of a container that house all the PV specified by vgcreate or vgextend command. Conceptually, you should regard Volume Group as a virtual hard disk, as you can see later that it’s possible to “partition” the Volume Group into Logical Volume (LV).

The -s option switches specify the physical extent size (PE size) of the volume group. If this is not specifying, the default PE size is 4MB, which is best for most applications.

The maximum number of PE per Logical Volume (LV) is not applicable in LVM2. However, high number of PE could affect LVM tool performance.

As such, set a bigger PE size could effectively reducing number of PE per VG and LV (if the VG is big enough).

Take note that the name of VG must not conflict with existing VG. To list existing VG in system, execute vgscan

5) Next, we proceed to partition Volume Group into Logical Volume. A file system can only be built on Logical Volume (LV) but not Volume Group (VG). Therefore, at least one LV must be created per VG. For example, this lvcreate command create a 400MB Logical Volume (virtual disk partition) called lvol3 in the Volume Group called vg7:

lvcreate -L 400M -n lvol3 vg7

Similar to VG, the name of LV must not crash with the existing LV in the same VG. Again, this can be verified by executing lvscan

To use all free Physical Extent in Volume Group for Logical Volume, you can use -l option switch to specify the number of PE to create the LV. The number of free PE in Volume Group vg7 can be checked by executing vgdisplay vg7

6) Now, with the new Logical Volume (lvol3), we can create file system on this virtual disk partition. For example, this mkfs command create the Linux EXT3 file system on Logical Volume /dev/vg7/lvol3, with -m 2 option switch to specify 2% of the file system blocks reserved for super-user.:

mkfs -t ext3 -m 2 -v /dev/vg7/lvol3

The full path of logical volume can be checked by executing lvscan command.

7) Once the mkfs successfully creates EXT3 file system, it’s ready to mount the new file system. First, create a directory as mount point, let say this:

mkdir /NewVGMnt

8) Then execute the mount command to mount the new file system to /NewVGMnt:

mount -t ext3 /dev/vg7/lvol3 /mnt/NewVGMnt

To verify the mount point, just type df -h command to confirm it’s done successfully. To enable Linux automatically mount the new file system during boot-up, include this new file system to /etc/fstab system file.

How To Add Raw Device Mapping In Red Hat Enterprise Linux 5?

Walker — Sun, 08 Feb 2009 17:15:03 +0000

Although I can’t remember the detail of steps to create raw device in SCO UNIX for Informix DBMS, I do remember it was a scary process for me as junior administrator.

Then, we moved on to Red Hat Linux 8 Professional. With Red Hat Linux, the process of creating raw device for DB2 database system was pleasant.

However, there was a little change on how to properly and persistently define raw device permission mode, as the database application moved to RHEL4 platform.

Now, Red Hat Enterprise Linux 5 is again introduces different steps to create raw device, as I just came across this in an email subscription related to RHEL5.

On top of the configuration changes, there is even a short note to remind all raw device fans AGAIN that the rawio is deprecated and this interface is scheduled for removal from future releases.

The legacy applications (majority are DBMS) that rely on rawio for performance sake should have code changes to support opening block device with O_DIRECT flag.

How to create raw device mapping in RHEL 5?

According to Red Hat Magazine article, here is the simplified step for my reference when our infrastructure team decides to go ahead with the upgrade of RHEL 4 to RHEL 5.

First, edit /etc/udev/rules.d/60-raw.rules to bind the hard disk to raw device, one line per record of mapping. (Consult Linux man page for udev related information).

There are two ways to define such mapping, but I prefer the easier way. For example, this line defines a mapping of first SCSI hard disk (/dev/sda) to first raw device (/dev/raw/raw1):

ACTION=="add", KERNEL=="sda", RUN+="/bin/raw /dev/raw/raw1 %N"

Next, add another line to define a persistent raw device permission mode (if the default permission mode is not suitable for my case):

ACTION=="add", KERNEL=="raw*", OWNER=="root", GROUP=="disk", MODE=="0660"

Lastly, to create the raw devices by executing /sbin/start_udev shell script. To check if the raw devices are created, execute raw -qa

Using IBM DB2 Monitoring Tool db2pd To Document Database Server Profile

Walker — Sun, 08 Feb 2009 08:52:21 +0000

One of the jobs of system administrator is to profile each server. This could be a simple job, but sometime it’s not as simple as it seems to be, especially for junior administrator.

Strictly speaking, db2pd is a monitoring tool, not a special utility to generate database server profile.

However, this IBM DB2 utility retrieves information from database system memory sets which some of the information are useful for documenting server profile.

For example, db2pd -osinfo reports the number of physical CPU and related information (single core or multiple core, CPU core speed, CPU load, etc), free and used memory, IPC resource (shared memory, semaphore, and message queue), etc. (See “How to detect a single or multi-core CPU is installed in Linux“).

Similar to db2level, db2pd -V or db2pd -version reports the DB2 version and FixPak level related information.

The db2pd -inst output the detail of DB2 instance level information, such as database uptime, database manager configuration, etc.

To view most information in single output, db2pd -everything tells you all information found on all database partitions.

If you only interested in a particular database called sample, first establish a connection to the target database, e.g. db2 connect to sample in this example. Then, proceed to db2pd command, such as:

To view buffer pools setup and related information (In DB2 version 9.1, db2pd also provides bufferpool statistics, such as hit ratio):

db2pd -db sample -bufferpools

To view table spaces type (SMS or DMS) and associated table space containers statistics (total useable pages, used pages, free pages). The db2pd command output seems to be easier for me to write a shell script to automatic recording table space utilization statistics :-)

db2pd -db sample -tablespaces

For more db2pd related information, refer to IBM DB2 Information Center Home of respective version. For example:

db2pd of DB2 version 8.2 for Linux, UNIX, and Windows operating systems (LUW).
db2pd of DB2 version 9.1 for Linux, UNIX, and Windows operating systems (LUW).
db2pd of DB2 version 9.5 for Linux, UNIX, and Windows operating systems (LUW).

How To Check What Kernel Build Options Enabled In The Linux Kernel?

Walker — Thu, 20 Nov 2008 16:41:07 +0000

Linux Kernel Build Options is the list of optional Linux kernel features that a system engineer can explicitly turn on or off during kernel compilation.

By selectively enabling Kernel Build Options, Linux administrator can build an optimized Linux kernel for a specific system crafted for particular purpose (e.g. Linux firewall, router, database server, etc).

Now, how could you tell what are the Kernel Build Options enabled in the Linux kernel running on production server, if you did not build it?

My ex-co phoned me just now and asked how could he check or confirm his Red Hat Enterprise Linux server supports the “secret” Linux magic SysRq key, which requires CONFIG_MAGIC_SYSRQ option enabled at kernel compile time.

The magic SysRq key is a key combination using the SysRq key (Print Screen) that allows user to perform low-level commands regardless of the Linux kernel’s state (hang or panic).

Since it’s a standard RHEL installation, I suggested him to take a look on Linux kernel configuration file that installed to /boot partition.

It’s a (recommended) practice of copying Linux kernel configuration file to /boot partition each time after the kernel image is compiled and installed to this partition, to serve purpose of documentation and reference.

In his RHEL 4 server, there two config files exists in /boot partition, one for SMP and another one is setup for non-SMP kernel compilation.

For accuracy, execute uname -r to print the kernel release and look for the corresponding config file of kernel release reported by uname -r command (as shown in the screenshot):

^{How to verify some specific Linux Kernel Build Options are enabled for the running Linux kernel?}

In this case, the correct Linux kernel configuration to look for is /boot/config-2.6.9-42.ELsmp and this command confirms that his RHEL4 kernel supports the magic SysRq key:

cat /boot/config-2.6.9-42.ELsmp | grep CONFIG_MAGIC_SYSRQ

He can enable or disable this supported feature by manipulating /proc/sys/kernel/sysrq or kernel.sysrq.

How To Fix Telnet Rejection Error of Name or Service Not Known: Illegal Seek

Walker — Wed, 19 Nov 2008 17:16:08 +0000

We all know that telnet is a good remote access protocol in the old days. Now, we prefer SSH protocol because SSH is a secure protocol, i.e. it’s not easy to hack.

However, for some reasons, telnet server still installed for some (Microsoft Windows) users who desperately need remote access facility. (Maybe telnet server will go into history when Windows start to bundle Putty or its own SSH client).

So, this is what happen here, that we have to install and enable the insecure telnet server on all Red Hat Enterprise Linux servers, for obvious reason.

Problem happen today when one user reported that he cannot telnet to the server, with an rejection error message that said “GetAddrInfo: : Success. Name or service not known: Illegal seek” (as seen in the following screenshot taken when I telnet to localhost in a SSH session):

How to fix this so-called “Name or service not known: Illegal seek” error (replied by the telnet daemon)?

Well, I guess this has something to do with DNS resolution. It was working fine until we changed the Linux hostname on yesterday. The hostname is not registered to DNS servers that defined in /etc/resolv.conf file and there is no hostname-to-IP mapping in /etc/hosts file as well.

So, to try out the possible solution, I add in hostname-to-IP mapping in /etc/hosts file, and it works:

192.168.20.21      WalkerNews      WalkerNews.net

[ assuming the hostname is WalkerNews and its IP address is 192.168.20.21]

I am not sure (because I haven’t tried) the problem will be fixed, if I remove the hostname-IP mapping in /etc/hosts and register the hostname-IP to DNS servers that defined in /etc/resolv.conf file. (I bet this will work, too).