Tag: mount

How to Perform Linux Data Recovery

By Kuldeep Kulmii

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.

Stellar Phoenix Linux Data Recovery is a risk free Linux recovery utility to recover your lost, deleted, formatted or inaccessible data from ext2, ext4, ext3, FAT and NTFS file system based volumes. Moreover, with step-wise-instructions based GUI, the software can be easily used by any user without much technical knowledge.

Kuldeep a techno geek is a technical writer doing research on different file system in linux like Ext2, Ext3. And Ext4. He is also interested in linux data recovery, Linux Partition Recovery And Linux file recovery. He is currently working with http://www.data-recovery-linux.com

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How to Solve Zero Length File Problem in Linux’s Ext4 File System

By Tom Patrick

The ext4 (fourth extended) is a journaled file system of Linux that has many benefits compared to its predecessors, such as support for backward compatibility, large file system, delayed allocation, etc. However, the delayed allocation feature sometimes poses problems for the Linux system. The Linux system based on ext4 file system may encounter inconsistencies in the files in case of a power surge. To overcome this behavior, you should take appropriate corrective measures. However, if no method employed by you is successful then you should use a third-party Linux recovery software to do the needful.

Consider a scenario wherein you are working on a Linux system. Suddenly, there is a power loss and the system shuts down abruptly. When the power is restored, you switch on the system and find that the files that you created just before the crash are showing zero bytes.

Cause:

The most possible cause for such behavior is the delayed allocation feature. What happens is when a file is closed after creation, the data blocks are allocated for the file after a minute or so. Because of this, the metadata of the modified file will show zero bytes as its size. The data allocation is done after the delayed allocation is over. Hence, in the case of a power surge the new file is considered as an empty file.

Resolution:

To resolve the issue, you can use the following methods:

Mounting the file system using “data write-back”

Using three patches designed for ext4 file system: The three patches (bf1b69c0, f32b730a, and 8411e347) enforce any file with delayed allocation will be allocated immediately when a file is created.

Mount the ext4 file system with the nodealloc mount option

Mount the system with the data=alloc-on-commit option: This would ensure that all blocks that had delayed allocation would be allocated and moved to disk before a commit takes place.

However, if you still are not able to recover the lost files then you should use a third-party Linux recovery software to perform data recovery for Linux system. Such read-only tools are able to recover lost data without overwriting the original data.

Tom Patrick is a magazine editor currently researching on linux recovery

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