ARMONK, N.Y., Nov. 20, 2014 /PRNewswire/ -- IBM (NYSE: IBM) today announced that it is bringing a greater level of control, security and flexibility to cloud-based application development and delivery with a single-tenant version of Bluemix, IBM's platform-as-a-service. The new platform enables developers to build ap...
|By Brian Carrier||
|August 12, 2005 03:00 PM EDT||
The file we are trying to recover is /home/carrier/oops.dat and we can see it previously allocated to inode 415,926. The "(28)" shows us that the directory entry structure is 28 bytes long, but we don't care about that.
File Carving Recovery
The first recovery technique, called file carving, uses signatures from the deleted file. Many file types have standard values in the first bytes of the file header, and this recovery technique looks for the header value of the deleted file to determine where the file may have started. For example, JPEG files start with 0xffd8 and end with 0xffd9. To recover a deleted JPEG file, we would look at the first two bytes of each block and look for one with 0xffd8 in the first two bytes. When we find such a block, we look for a block that has 0xffd9 in it. The data in between are assumed to be the file. Unfortunately, not all file types have a standard footer signature, so determining where to end is difficult. An example of an open source tool that does file carving is foremost and there are several commercial options as well.
We can run a tool like foremost on the full file system, but we'll probably end up with way too many files, including allocated ones. We therefore want to run it on as little data as possible. The first way we can restrict the data size is to examine only the block group where the file was located. Remember that inodes and blocks for a file are allocated to the same block group, if there is room. In our case, we know which inode the file used and therefore we can examine only the blocks in the same group. The imap command in debugfs will tell us to which block group an inode belongs:
debugfs: imap <415926>
Inode 415926 is part of block group 25
located at block 819426, offset 0x0a80
The output of the fsstat command in TSK would also tell us this:
# fsstat /dev/hda5
Inode Range: 408801 - 425152
Block Range: 819200 - 851967
We next need to determine the blocks that are in the block group of the deleted file. We can see them in the previous fsstat output, but if we're using debugfs , we'll need to calculate the range. The stats command gives us the number of blocks in each group:
Blocks per group: 32768
Since we are looking at block group 25, then the block range is from 819,200 (25 * 32,768) to 851,967 (26 * 32,768 - 1). By focusing on only these blocks, we are looking at 128MB instead of the full file system. Although if we can't find the file in these blocks, we'll still need to search the full file system.
The next step to reduce the data we analyze is to extract the unallocated blocks from the file system because that is where our deleted file will be located. debugfs does not currently allow us to extract the unallocated space from only a specific block group, so we will need to use the dls tool from TSK.
# dls /dev/hda5 819200-851867 > /mnt/unalloc.dat
The above command will save the unallocated blocks in block group 25 to a file named /mnt/unalloc.dat. Make sure that this file is on a different file system because otherwise you may end up overwriting your deleted file.
Now we can run the foremost tool on the unallocated data. foremost can recover only file types for which it has been configured. If foremost doesn't have the header signature for the type of the deleted file, you'll need to examine some similar files and customize the configuration file. We can run it as follows:
# foremost -d -i /mnt/unalloc.dat -o /mnt/output/
The -d option will try to detect which blocks are indirect blocks and won't include them in the final output file. The /mnt/output/ directory will contain the files that could be recovered. If your file is not in there, you can expand your search to all unallocated blocks in the file system instead of only the blocks in the block group.
The second method for trying to recover the files is to use the journal. We already saw that inode updates are first recorded in the journal, but the important concept here is that the entire block in which an inode is located is recorded in the journal. Therefore, when one inode is updated, the journal will contain copies of other inodes stored in the same block. The previous version of our deleted file's inode may exist in the journal because another file was updated before the deletion.
The easiest way to look for previous versions of the inode is by using the logdump -i command in debugfs:
debugfs: logdump -i <415926>
Inode 415926 is at group 25, block 819426, offset 2688
Journal starts at block 1, transaction 104588
FS block 819426 logged at sequence 104940, journal block 2687
(inode block for inode 415926):
Inode: 415926 Type: regular Mode: 0664 Flags: 0x0
User: 500 Group: 500 Size: 2048000
Blocks: (0+12): 843274 (IND): 843286
In this case, we found a previous copy of the inode and the file content blocks are listed on the last line. The last line shows that the first block of the file is 843,274 and the next 12 blocks in the file system are the next 12 blocks in the file. The file is large and requires an indirect block, which is located in block 843,286. So far, all blocks are consecutive and there was no fragmentation. Block 843,286 contains the rest of the block addresses, so we should try to look at a previous version to learn where the rest of the file is located. We can see if there is a copy in the journal using logdump -b:
debugfs: logdump -b 843286 -c
Unfortunately, we don't find a copy of the block that contains the original list of block pointers so, if we want to recover the file, we need to assume that the remaining file content is stored in block 843,287 and onward. A more advanced approach would also consider which blocks are currently allocated and skip over those. The data can be extracted with tools such as dd or the Linux Disk Editor. The journal can also be searched using the jls and jcat tools from TSK.
File recovery with Ext3 is not a trivial matter, which reinforces the concept of making backups of important files. If the file was not fragmented, then searching for its header signature can be useful, but the tool needs to know to ignore the indirect blocks and where to stop copying (not all files have a standard footer signature). Restricting the search to the local block group can help save time. The journal could be useful if files near the deleted file were recently updated and a previous version of the inode existed, but this is not always guaranteed and the file's indirect block may not exist.
References and Bibliography
- Carrier, B. "The Sleuth Kit": www.sleuthkit.org
- Carrier, C. (2005). File System Forensic Analysis. Addison-Wesley.
- Crane, A. "Linux Ext2fs Undeletion mini-HOWTO." February 1999: http://tldp.org/HOWTO/Ext2fs-Undeletion.html
- Diedrich, O. "e2undel": http://e2undel.sourceforge.net/
- Farmer, D., and Venema, W. (2004). Forensic Discovery. Addison-Wesley.
- Heavner, S.D. "Linux Disk Editor": http://lde.sourceforge.net/
- Kendall, K.; Kornblum, J.; and Mikus, N. "Foremost": http://foremost.sourceforge.net/
- Ts'o, T. "E2fsprogs": http://e2fsprogs.sourceforge.net/
- Tweedie, S. "EXT3, Journaling Filesystem." July 2000: http://olstrans.sourceforge.net/release/ OLS2000-ext3/OLS2000-ext3.html
|theusr 07/09/09 09:29:00 AM EDT|
The figure 2 maybe misleading: the links between the address blocks and the file content are still there (though the address blocks are unallocated), that what's make the recovery possible.
|Mike Kay 01/15/08 03:57:07 PM EST|
Excellent article. Followed it step by step and successfully recovered a .XLS spreadsheet that had been deleted from the /tmp folder on Ubuntu Gutsy. It also found an associated .jpg that I wasn't looking for!
Saved me hours of retyping. Thanks a lot.
|Jahangir 10/22/07 05:26:36 PM EDT|
This was really the best article i could find inspite of 3 hrs of googling.
But what if you are trying to recover a 6GB VM.
|ruintower 04/23/06 09:07:29 PM EDT|
Trackback Added: ext3 undelete; I “mis-deleted” a big file several days ago. So I umount the the partition immediately and searched the recovery method because I knew (but forgot) some methods to recovery file in Linux. However, the result is disappointed. Alt...
|marco 03/13/06 08:04:20 AM EST|
U have saved my life.
U are a GURU,
|marco 03/13/06 08:04:04 AM EST|
U have saved my life.
U are a GURU,
Dec. 19, 2014 05:00 AM EST Reads: 2,961
SYS-CON Events announced today that IDenticard will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. IDenticard™ is the security division of Brady Corp (NYSE: BRC), a $1.5 billion manufacturer of identification products. We have small-company values with the strength and stability of a major corporation. IDenticard offers local sales, support and service to our customers across the United States and Canada. Our partner network encompasses some 300 of the world's leading systems integrators and security s...
Dec. 19, 2014 04:00 AM EST Reads: 2,380
DevOps Summit 2015 New York, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long development cycles that produce software that is obsolete at launch. DevOps may be disruptive, but it is essential.
Dec. 18, 2014 09:45 PM EST Reads: 1,475
“In the past year we've seen a lot of stabilization of WebRTC. You can now use it in production with a far greater degree of certainty. A lot of the real developments in the past year have been in things like the data channel, which will enable a whole new type of application," explained Peter Dunkley, Technical Director at Acision, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 18, 2014 11:30 AM EST Reads: 1,582
SYS-CON Events announced today that Windstream, a leading provider of advanced network and cloud communications, has been named “Silver Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Windstream (Nasdaq: WIN), a FORTUNE 500 and S&P 500 company, is a leading provider of advanced network communications, including cloud computing and managed services, to businesses nationwide. The company also offers broadband, phone and digital TV services to consumers primarily in rural areas.
Dec. 18, 2014 11:00 AM EST Reads: 2,688
The major cloud platforms defy a simple, side-by-side analysis. Each of the major IaaS public-cloud platforms offers their own unique strengths and functionality. Options for on-site private cloud are diverse as well, and must be designed and deployed while taking existing legacy architecture and infrastructure into account. Then the reality is that most enterprises are embarking on a hybrid cloud strategy and programs. In this Power Panel at 15th Cloud Expo (http://www.CloudComputingExpo.com), moderated by Ashar Baig, Research Director, Cloud, at Gigaom Research, Nate Gordon, Director of T...
Dec. 18, 2014 10:30 AM EST Reads: 2,869
The Internet of Things is not new. Historically, smart businesses have used its basic concept of leveraging data to drive better decision making and have capitalized on those insights to realize additional revenue opportunities. So, what has changed to make the Internet of Things one of the hottest topics in tech? In his session at @ThingsExpo, Chris Gray, Director, Embedded and Internet of Things, discussed the underlying factors that are driving the economics of intelligent systems. Discover how hardware commoditization, the ubiquitous nature of connectivity, and the emergence of Big Data a...
Dec. 18, 2014 10:15 AM EST Reads: 2,656
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 18, 2014 10:00 AM EST Reads: 2,303
"People are a lot more knowledgeable about APIs now. There are two types of people who work with APIs - IT people who want to use APIs for something internal and the product managers who want to do something outside APIs for people to connect to them," explained Roberto Medrano, Executive Vice President at SOA Software, in this SYS-CON.tv interview at Cloud Expo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 18, 2014 09:00 AM EST Reads: 2,076
Nigeria has the largest economy in Africa, at more than US$500 billion, and ranks 23rd in the world. A recent re-evaluation of Nigeria's true economic size doubled the previous estimate, and brought it well ahead of South Africa, which is a member (unlike Nigeria) of the G20 club for political as well as economic reasons. Nigeria's economy can be said to be quite diverse from one point of view, but heavily dependent on oil and gas at the same time. Oil and natural gas account for about 15% of Nigera's overall economy, but traditionally represent more than 90% of the country's exports and as...
Dec. 18, 2014 06:00 AM EST Reads: 1,164
The Internet of Things is a misnomer. That implies that everything is on the Internet, and that simply should not be - especially for things that are blurring the line between medical devices that stimulate like a pacemaker and quantified self-sensors like a pedometer or pulse tracker. The mesh of things that we manage must be segmented into zones of trust for sensing data, transmitting data, receiving command and control administrative changes, and peer-to-peer mesh messaging. In his session at @ThingsExpo, Ryan Bagnulo, Solution Architect / Software Engineer at SOA Software, focused on desi...
Dec. 17, 2014 11:15 PM EST Reads: 2,103
"At our booth we are showing how to provide trust in the Internet of Things. Trust is where everything starts to become secure and trustworthy. Now with the scaling of the Internet of Things it becomes an interesting question – I've heard numbers from 200 billion devices next year up to a trillion in the next 10 to 15 years," explained Johannes Lintzen, Vice President of Sales at Utimaco, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 17, 2014 11:00 PM EST Reads: 2,134
"For over 25 years we have been working with a lot of enterprise customers and we have seen how companies create applications. And now that we have moved to cloud computing, mobile, social and the Internet of Things, we see that the market needs a new way of creating applications," stated Jesse Shiah, CEO, President and Co-Founder of AgilePoint Inc., in this SYS-CON.tv interview at 15th Cloud Expo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 17, 2014 08:00 PM EST Reads: 2,109
SYS-CON Events announced today that Gridstore™, the leader in hyper-converged infrastructure purpose-built to optimize Microsoft workloads, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Gridstore™ is the leader in hyper-converged infrastructure purpose-built for Microsoft workloads and designed to accelerate applications in virtualized environments. Gridstore’s hyper-converged infrastructure is the industry’s first all flash version of HyperConverged Appliances that include both compute and storag...
Dec. 17, 2014 06:30 PM EST Reads: 2,018
Today’s enterprise is being driven by disruptive competitive and human capital requirements to provide enterprise application access through not only desktops, but also mobile devices. To retrofit existing programs across all these devices using traditional programming methods is very costly and time consuming – often prohibitively so. In his session at @ThingsExpo, Jesse Shiah, CEO, President, and Co-Founder of AgilePoint Inc., discussed how you can create applications that run on all mobile devices as well as laptops and desktops using a visual drag-and-drop application – and eForms-buildi...
Dec. 17, 2014 11:45 AM EST Reads: 2,214
We certainly live in interesting technological times. And no more interesting than the current competing IoT standards for connectivity. Various standards bodies, approaches, and ecosystems are vying for mindshare and positioning for a competitive edge. It is clear that when the dust settles, we will have new protocols, evolved protocols, that will change the way we interact with devices and infrastructure. We will also have evolved web protocols, like HTTP/2, that will be changing the very core of our infrastructures. At the same time, we have old approaches made new again like micro-services...
Dec. 16, 2014 11:45 PM EST Reads: 2,084
Code Halos - aka "digital fingerprints" - are the key organizing principle to understand a) how dumb things become smart and b) how to monetize this dynamic. In his session at @ThingsExpo, Robert Brown, AVP, Center for the Future of Work at Cognizant Technology Solutions, outlined research, analysis and recommendations from his recently published book on this phenomena on the way leading edge organizations like GE and Disney are unlocking the Internet of Things opportunity and what steps your organization should be taking to position itself for the next platform of digital competition.
Dec. 15, 2014 11:45 PM EST Reads: 2,507
The 3rd International Internet of @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that its Call for Papers is now open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
Dec. 15, 2014 10:30 AM EST Reads: 8,122
As the Internet of Things unfolds, mobile and wearable devices are blurring the line between physical and digital, integrating ever more closely with our interests, our routines, our daily lives. Contextual computing and smart, sensor-equipped spaces bring the potential to walk through a world that recognizes us and responds accordingly. We become continuous transmitters and receivers of data. In his session at @ThingsExpo, Andrew Bolwell, Director of Innovation for HP's Printing and Personal Systems Group, discussed how key attributes of mobile technology – touch input, sensors, social, and ...
Dec. 15, 2014 10:00 AM EST Reads: 3,274
In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect at GE, and Ibrahim Gokcen, who leads GE's advanced IoT analytics, focused on the Internet of Things / Industrial Internet and how to make it operational for business end-users. Learn about the challenges posed by machine and sensor data and how to marry it with enterprise data. They also discussed the tips and tricks to provide the Industrial Internet as an end-user consumable service using Big Data Analytics and Industrial Cloud.
Dec. 15, 2014 10:00 AM EST Reads: 2,397