Technology And Computer|

Linux has gained enough popularity for its new and updated features. Usually, this operating system is considered as the most regularly upgraded application and hence, with Linux, many users feel that they are having the advantage of using the most recent technologies. Even some feel that Linux is free from virus attack and other data loss problems. However, it is the fact that the technology has nothing to do with data loss. Linux systems also undergo severe data loss situations, leaving the system drive completely inaccessible. Under such cases, you can take the help of any Linux data recovery software to retrieve your data back.

Data loss in Linux can be in any form, starting from the accidental/intentional deletion, formatting of the media, virus/malware attack, operating system malfunction, file system corruption or any other software/hardware contradiction etc.

Whatever, be the reason behind the failure of the Linux system, it is your valuable data in the media which suffers the most. Some data can be urgently required, some are the result of months of research work and some even can never be recreated. In such situations, loss of them caused severe business loss and mental trauma.

Among all the odds, if you have taken regular backups of your data, you always resides at the safe side and can restore the data from a recently taken valid backup. But, if you have not taken any recent backup, you are under serious trouble for sure.

But, among all these troubles of data loss, the good fact is that data from the troubled Linux drive never gets lost permanently. Therefore, if you can take strict measures to avoid overwriting the data in the drive, and run any efficient Linux file recovery utility, then, all you lost data can be easily recovered back.

These undelete Linux applications can work on any Linux operating system based computer system and can recover your lost, deleted, formatted or inaccessible data effectively. These utilities have been developed with many advanced scanning algorithms to dig into the storage media throughly and are completely read-only in nature. Moreover, with detailed instructions at every step and highly graphical user interfaces, they are pretty easy to use even with much technical knowledge.

However advanced the technology may be and whatever precautions we may take, data loss is almost inevitable. Though Linux operating system is often improved upon its previous versions than any of its counterparts, still there are a number of reasons, for which data can be lost in a Linux operating system based computer. In a Linux computer, the fstab (/etc/fstab) and mtab (/etc/fstab) are the two most crucial directories. Without these directories, the operating system could not be able to locate neither the existing hard drive volumes nor the mounted drives on your system. For this reason, the system fails to boot and all your data in the hard drive becomes inaccessible. In such situation of data loss, you need any Linux data recovery software to recover back the lost or inaccessible data.

Facts about ‘fstab’ and ‘mtab’ directories:

• The fstab or ‘file systems table’ is a system directory within the Linux operating system. This system configuration file contains information about all the available hard drives and volumes attached to the system. The file tells, the way, hard drive volumes are initialized and integrated through the file system. Moreover, it lists the details of the file systems, which are accessed by the ‘fsck command.

• The mtab or ‘mounted file systems table’ is also part of system configuration and lists all the currently mounted file systems on your Linux system. The file retains every detail of the mounted volumes, that is whether mounted manually or automatically and is automatically updated once the mount command is triggered against any drive or volume.

Sometimes, while accessing the Linux drives or the mounted volumes you may come across error messages related to the mounted file system and all the files and directories become inaccessible. The error message that you may have encountered can be read as below:

“Cannot read table of mounted file systems”

The above error is caused due to the corruption of ‘fstab’ or ‘mtab’ directories. Thus, the file system fails to mount and the data remains inaccessible thereof.

Such situation of data loss can only be dealt by any efficient Linux data recovery utility. These applications are meant to recover the lost, deleted, formatted or inaccessible data from the Linux file system based volumes. Moreover, these helpful utilities are completely safe to use and come with detailed instructions, so that can be used without any prior knowledge.

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Linux is the UNIX like operating system that uses the Linux kernel of Monolithic type. The OS is being installed on a vast range of tablet computers, mobiles, video game consoles, mainframes, super computers etc. Even, statistics says that as, server OS, LINUX accounts more than 50% of the whole global installations. Also,over the years, Linux operating system has gained fair amount of popularity among the common home users with the Fedora, Ubuntu and OpenSUSE distributions. Moreover, with the egression of smart phones, netbooks etc, which are running on embedded LINUX, the operating system has been more closely used by many users. Though Linux has advanced technology and features, sometimes, some errors  lead to data loss or inaccessibility and you need to look for any Linux data recovery software to recover back your valuable data.

In day to day usage of a Linux system, there can be enormous possibility of data loss situations, and you may not always successful in trouble shooting the system to gain access of your data. Hence, if you don’t have a valid backup available or failed to restore the data from the backup, Linux recovery is the answer to bring back your data.

Common data loss situations in Linux:

Error – Mount wrong fs type, bad option, bad super block on /dev/hdb2.
Error – Too many mounted file systems.
File system error.
Grub Error 12 – Invalid device requested.
Grub Error  17 – Can not mount selected partition.

There can be many such errors leading to the loss or inaccessibility of your Linux data. In such cases, if you are a technical person, then you can trouble shoot at the low-level. You can  run the ‘fsck’ command to detect and fix such error. Prior to running the ‘fsck’ command, first, you need to go to the single user mode. Then, you have to unmount the file system partition, you are going to work upon, if it is not the root file system. If you don’t take enough care to unmount the file system, the ‘fsck warns you, such as- ‘The file system is mounted, do you want to continue anyway?’ Saying yes to the message, may result in the loss of your data, because, at times, ‘fsck’ writes directly to the disk.

If you need to check the root file system based partition, you have to boot the system in single user mode and run the ‘fsck’ with a ‘-b’ option so that it will run in a read-only mode. Also, the ‘-b’ option directly go to the ‘init’ and makes an emergency booting while skipping the other start-up scripts.

Sometimes, ‘fsck’ fails to run or exits without running at all. At that time, you need to force run the utility with ‘-f’ option. This is a case of severe corruption and you need to give additional information to ‘fsck’, such as the size of the alternate superblock or the address of the superblock to fetch the data and fix the error.

However, sometimes, these low-level recovery process is tedious as well as risky with respect to your valuable data. Hence, you can go for any Linux data recovery software, which can recover the data for you safely.

In a Linux operating system based computer, directories, blocks, sockets, files, and other items are referred by their corresponding file descriptors. File descriptor is one of the significant data structures of Linux operating system. It is very essential for the file descriptor to be consistent for proper working of your system. In case it is damaged, you can not access your precious data from the disk and face severe data loss situations. In such cases, you need to opt for Linux data recovery solutions.

If you encounter any error from your system related to file descriptor corruption, it can be due to corruption to the Linux file system. File system corruption is a major reason of data loss and cause serious problems for you. For a practical instance of this problem with your Linux system, you may encounter the following error message when you attempt to access data from your Linux hard drive-

“Bad file descriptor”

The above error may also occur while booting your system or mounting a hard drive volume. It renders your precious data inaccessible. At this point, you need to find out the root of this problem and fix it using Linux recovery solutions.

Grounds of the problem-
You may encounter this behavior of Linux operating system due to any of the following reasons-

Linux uses /dev/null file that removes all data, which is written to the file after reporting that write process is completed successfully. You might encounter the file description problems if the file is deleted.
If this error occurs while accessing any file from the hard drive, it can be due to corrupt disk blocks or file system corruption.

Resolution
Try using the below methods to sort out this issue-
To fix overwritten or deleted /dev/null file problems, you are required to replace the file with suitable iNode.Run fsck command on the affected Linux hard drive to resolve file system inconsistency and hard drive integrity issues. Before you run this command, file system must be un-mounted and system must be running in single-user mode.

Restore data from the most recent backup. It is an efficient Ext3 recovery solution to get your precious data back.If none of the above methods work, use third-party Linux recovery software to perform data recovery Linux. The applications are capable of retrieving your significant data in all data loss situations.

What is a BSD Unix?

BSD family of Unix systems is based upon the source code of real Unix developed in Bell Labs, which was later purchased by the University of California – “Berkeley Software Distribution”. The contemporary BSD systems stand on the source code that was released in the beginning of 1990′s (Net/2 Lite and 386/BSD release).

BSD is behind the philosophy of TCP/IP networking and the Internet thereof; it is a developed Unix system with advanced features. Except for proprietary BSD/OS, the development of which was discontinued, there are currently four BSD systems available: FreeBSD, NetBSD, OpenBSD and Mac OS X, which is derived from FreeBSD. There are also various forks of these, like PC-BSD – a FreeBSD clone, or MirOS, an OpenBSD clone. The intention of such forks is to include various characteristics missing in the above BSD systems, on which these (forks), no matter how well they are designed, only strongly depend. PC-BSD, for example, has more graphical features than FreeBSD, but there are no substantial differences between these two. PC-BSD cannot breathe without FreeBSD; FreeBSD or OpenBSD are independent of one another.

What is Linux?

Albeit users like to use the term “Linux” for any Linux distro including its packages (Red Hat Linux, Mandrake Linux, etc.), for IT professionals Linux is only the kernel. Linux started in 1991, when its author, Linus Torvals, began his work on a free replacement of Minix. Developers of quite a few Linux system utilities used the source code from BSD, as both these systems started parallelly in about the same time (1992-1993) as Open Source.

Today, there are a few, if not many developers of their own kernels/operating systems (FreeDOS, Agnix, ReactOS, Inferno, etc.), but these guys simply missed the right train in the right hour. They did not lose anything except for the fact that they may be even better programmers, but without the public opinion acknowledging this at large. Linus built his fame also from work of many developers and he went on board in the right time. Linus deserves a credit as a software idea policy maker and he helped very much in this respect.

(Open)BSD vs Linux

It is often difficult to say what is better if you compare two things without regarding the purpose of their use. Mobile Internet may appear better for someone who travels often, but for people working at home such mobility is not necessary. In this view, it is a stupid question when someone asks: “What is better, a mobile or static Internet?” It all depends…

If you compare Linux and OpenBSD in their desktop environment features, Linux offers more applications than OpenBSD; but in a server solution BSD systems are known to be robust, more stable and secure, and without so many patches distributors release soon after their new version of Linux slithered to light.

BSD systems are based upon real Unix source code contrary to Linux, which was developed from scratch (kernel).

Differences between BSD and Linux

1) BSD license allows users/companies to modify a program’s source code and not to release changes to the public. In other words, BSD licenses allow commercial use and incorporation of a code into proprietary commercial products. This is how Microsoft incorporated BSD networking into their products and how Mac OS X earns money through muscles of FreeBSD.

Linux uses GPL license for most of the time (applications in Linux can also have a BSD license – or any license; it is up to developers how they decide). With a GPL-licensed program anybody can change the source code, but he or she MUST share it with the Open Source community to make sure that everybody will benefit from such a change.

2) BSD has the so-called “core system” (without packages). The core system consists of basic utilities (like ssh, fdisk, various commands like chmod or sysctl, manual pages, etc.) and anything beyond this is strictly seen as an add-on. Linux (not only the kernel, of course) is usually packaged as the whole system where this difference is not seen.

3) On BSD systems, all add-on packages are strictly installed into the /usr/local directory: documents to user/local/share/docs/application_name; themes and other things to /usr/local/share/application_name; binaries to /usr/local/bin/application_name. By application_name we mean a program’s name, so if you install IceWM, for example, its binary will be here: /usr/local/bin/icewm. With Linux, on the other hand, all applications get mostly installed into the /usr/bin directory.

4) BSD systems use the system of “ports”, which are fingerprints of applications in the /usr/ports directory, where a user may “cd” and execute a make command, which will download, via a directive contained in such a fingerprint’s code, the application’s source and the system will compile it as well. “Ports” are actually add-on packages for BSD systems and they are also packaged in packages repository of a concrete BSD system. They can be installed as binaries, too, with use of the “pkg_add” either directly from the Internet or locally. But “ports” have that advantage that if an author of any package makes a new version, a user can immediately get its newest/updated version. Packages released for a particular BSD version (like OpenBSD 4.1) are not updated and users have to wait for a new BSD release (like OpenBSD 4.2).

5) BSD systems have also their stable version. With FreeBSD, for example, you have a FreeBSD-Release (a version that can be used normally), FreeBSD-Stable (system more profoundly audited for bugs and security holes), and a development version – Current, which is not stable and not recommended for a regular use. Some Linux distributions started to imitate this philosophy, but with BSD systems this way of making distributions has become a rule.

6) Of course, the kernel is absolutely different.

7) BSD has FFS file system; it is the only file system on BSD’s contrary to Linux, where you can use dozens of file systems like ext2, ext3, ReiserFS, XFS, etc.

BSD systems divide their partitions internally. This means that after installing a BSD system to a hard disk, programs like fdisk, Partition Magic, Norton Ghost and many others will not see this internal division of a BSD (FFS) disk; thus, repartitioning of a disk is not such a pain when administrators require a rigorous partitioning (for /home, /tmp, /var, /etc directories). As a consequence, the naming convention also differs a little: a disk – /dev/ad0s3b in FreeBSD indicates that you deal with “slice” 3 (“s3″), which is the equivalent of Linux /dev/hda3; the internal “partition” has the name of a letter: “a”, “b”, “e”, etc. (“b” is a swap partition). BSD systems also use different naming conventions for devices (disks, etc.).

9) Unless you make a good kernel hack, BSD systems can only be installed into the primary partition. This is not the rule with Linux. However, as BSD systems offer the above-mentioned internal division of partitions, this is not any pain. PC architecture for disks (IDE) follows the rule that you can have only four primary partitions. We will illustrate this on Linux: /dev/hda1 (note: first partition on master disk on first IDE channel), /dev/hda2 (second partition), /dev/hda3 (third partition), /dev/hda4 (fourth partition). PC architecture allows creation of the so-called logical disk on a physical disk (/dev/hda5, /dev/hda6, etc.). You can have as many logical disks/partitions as you wish and you can also install Linux into these “logical disks”. On the other hand, installing a BSD OS into such a “logical partition” is not normally possible.

10) System configuration is manual for most of the time, but various clones like PC-BSD break this convention. The manual approach is a very good thing, as administrators have everything under control without being pushed to waste time in a labyrinth of bloated configuration menus. A good comparison is to imagine a car mechanic repairing the car’s engine covered by a thick blanket. To give you even a little better example – you will hardly find a Linux distro that does not have a default X startup (graphical environment). Of course, you can switch off the X environment during the installation configuration, but if you keep forgetting like me and forget to switch this off, or you have difficulties to find it in the menu somewhere, you realize that most Linux distributors do indeed impose on us only one approach – to put our fingers first on the thick blanket, then on the engine. If you are a good administrator, you do not usually trust vendors who program you how to use Linux – you are the boss and you must have your own freedom. However, in most cases you lose few hours instead by deactivating various services, which are, unfortunately, not even necessary but almost always activated by default. Linux is praised both for being a good desktop and server, but administrators of a good server do not need X. The more software is stored on your hard disk, the more security problems you will face, because it is impossible to audit every package in every unthinkable situation. Good and secure systems are always tight, light and simple.

11) All BSD systems have a Linux emulation support. Running BSD binaries on Linux is a little harder.

12) BSD systems have less support from driver vendors, thus they lag behind in this view (they are not worse, but many vendors support only Microsoft and Linux). With a BSD system you must carefully research the Internet for supported products/chipsets before purchasing any hardware.

13) BSD systems do not use the Unix System V “runlevel scripts” (initialization startup scripts) like Linux.

14) BSD kernels can be set to several security levels. This is also possible with Linux, but BSD’s have taken a very good care of this kernel-tuning feature, which makes it even impossible to change something in files in higher security levels – you cannot delete them.

15) BSD’s have everything under one ROOF. Various Linux programs are often not even compatible with other Linuces. For example, if you install a SuSE RPM package on Mandrake, it may not work. BSD’s have one solid crown of power. If you move from Linux to FreeBSD, you will soon find out that you got out of this chaos. Do you want a package? Just visit: http://www.freebsd.org/ports/ and download it. Unless its developer made some programming errors, it will always work.

16) Generally, BSD systems boot and reboot faster than Linux. Linux can do this, too, but it must be tuned. It is very surprising that Linux is shipped, on the one hand, on huge DVD’s and, on the other hand, it has a compressed kernel. BSD systems do not use (but they can) a default kernel that is compressed, thus the system boots always faster. As I mentioned earlier in this article, Linux vendors program users to use various, often unnecessary services. I do not need SAMBA (file and print services) and many other things as well. Linux reboot process takes longer because various services running on Linux need time for deactivation. Many Linux users do not even know what is the purpose of these services.

17) In comparison to BSD, most Linux distributions are overbloated. Few good users noticed this some time ago and a new trend in the Linux world started with ideas to get closer to a BSD-style use. One of such distributions is Gentoo Linux, but also Slackware Linux, which has preserved a very good shape since its first release (1993). The Gentoo “About” page (http://www.gentoo.org) says that, “Gentoo is a free operating system based on either Linux or FreeBSD…” Therefore, if you use Slackware or Gentoo, these Linuces will always reboot faster than any other Linux.

18) If you compile programs from ports, you will not stumble into compilation errors. BSD packagers prepare their packages carefully, so that users will always compile them successfully. This does not always happen with Linux.

Conclusion

I am the author of One Floppy CD Audio and MP3 Player, and a single floppy OpenBSD router. I really like all BSD systems. If you are interested, look into FreeBSD documentation, which is one of the best. It will give you a very good overview of history and hard work done in the development of these robust systems. Today, BSD Unices are the only quality alternative to Linux in the Open Source world.

Copyright (c) Juraj Sipos

Author’s website about FreeBSD and OpenBSD

Sometimes when you try to install device drivers on your Linux system, you might fail to do it. It could be due to incompatibility of the operating system Kernel with your device driver or device.

To work around this issue, you need to install the latest version of Linux kernel. It may include ‘forcedeth’ patch, which is capable of resolving most of the incompatibility issues.

In some cases, after installing the latest version of Kernel, when you reboot the Linux system, you might face the following error message:

“fsck.ext2: No such file or directory while trying to open /dev/hda8. The super block could not be read or does not describe a correct ext2 file system. If the device is valid and it really contains an ext2 file system (and not swap or ufs or something else) then the super block is corrupt, and you might try running e2fsck with an alternate super block: e2fsck -b 8193 <device> fsck failed.”

After this error message, neither the system boots nor any file can be accessed.

Grounds of the issue

As stated in the error message, this problem generally occurs due to super block corruption or file system corruption.

è Super block and file system are two most important data structure of Linux system. Proper functioning of both these is required for ensuring effective working of the system.

After corruption, the operating system could not locate the file and thus can not retrieve it.

Resolution

To work around this problem, you need to install a fresh copy of super block and file system. It is possible through formatting of the hard drive and reinstallation of operating system.

Though, it will remove the errors but will also erase all the data stored on your hard drive. It is the worst scenario of data loss and needs Linux data recovery to get it fixed.

Linux data recovery is feasible with the application of third party Linux recovery software known as Linux data recovery software. Linux recovery software is easy to use and thus allow you to have simple and fast data recovery Linux.

Stellar Phoenix Linux Data Recovery is the most advanced Linux recovery software offered by the data recovery giant- Stellar. This data recovery Linux software works well in all data loss cases and allows Linux data recovery for all sorts of files.

Stellar Phoenix Linux Data Recovery software is powerful enough to carry out efficient scanning of entire hard drive and extract all lost data from it. The user interface of this software is very interactive and thus does not require any sound technical knowledge from users’ side.

Kernel is a core component of Linux operating system, which works as an interface between the application and actual data processing performed at hardware level. It is responsible for managing all of the system resources. Kernel uses a device manager to make its functions easier. For example, Linux 2.6 kernel series uses udev. Basically udev manages the device nodes in root directory. It also handles /dev directory and all of the user space actions while removing/adding devices. In case if you use new version of the udev with Linux kernel 2.6.13 or earlier, you may not boot your system and access data from your hard drive. Issues with the udev file causes critical situations of data loss and need Linux Data Recovery to be handled.

The udev device manager in Linux dynamically offers only nodes for devices that are actually present on your system. Though, the devfs used to offer same functionality, but udev has a number of reasons to prefer it over devfs:

It supports unrelenting device naming that doesn’t depend upon the order of plugging of devices into system. Default udev setup offers persistent name for storage devices. Hard drive is recognized by the unique file system id.

The execution of udev is completely in user space, in place of kernel space. It could execute arbitrary programs for composing name for devices from properties of device, before creating the node.

The simplest method to use the udev on your Linux system is to let the device manager send events via a socket to Hardware Abstraction Layer (HAL) that would carry out further device-specific operations. For instance, HAL would notify other applications running on your system that new hardware resource has arrived though a broadcast message on D-Bus IPC system to all of the interested processes.

For proper working of your Linux system, it is essential for udev file to be stable. In case if it gets damaged due to any reason, your system would become inaccessible and you come across data loss issues. At this point, Data Recovery Linux is required to get your valuable data back.

Linux Recovery is potential through efficient and effective third-party tools, known as Linux Data Recovery software. The applications are completely safe and easy to use and carry out absolute recovery in most of the data loss situations.

Stellar Phoenix Linux Data Recovery is the most comprehensive and efficient utility for successful recovery. It recovers lost data from Ext4, Ext3, Ext2, FAT32, FAT16 and FAT12 file system volumes. The software is compatible with most of the major distributions of Linux operating system including Red Hat, Ubuntu, Fedora, SUSE and Mandriva.