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  • Persistent (purely functional) Red-Black trees on disk performance

    - by Waneck
    I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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  • Old query String hard coded 301 url redirection using htaccess

    - by Nilesh Toshniwal
    I have recently changed CMS of my website and now looking to redirect old urls like: oldpage.php?key=7cdb93c26 to some new urls but I want all of them in hard coded way and it should be a 301 redirect I tried the following rules but none of them work for me redirect 301 /oldpage.php?key=7cdb93c26 http://www.mynewsite.com/my-new-page.html redirect 301 "/oldpage.php?key=7cdb93c26" http://www.mynewsite.com/my-new-page.html RewriteRule ^oldpage.php?key=7cdb93c26$ http://www.mynewsite.com/my-new-page.html [L,R=301] RewriteRule ^oldpage.php?key=7cdb93c26$ /my-new-page.html [L,R=301]

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  • C++ IO with Hard Drive

    - by Tomas Cokis
    I was wondering if there was any kind of portable (Mac&Windows) method of reading and writing to the hard drive which goes beyond iostream.h, in particular features like getting a list of all the files in a folder, moving files around, ect. I was hoping that there would be something like SDL around, but so far I havn't been able to find much. Any ideas??

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  • Help understanding my hard drive / partitioning situation... Pictures Included! :)

    - by xopenex
    So I have installed windows 7, and two different distros of linux... I have read and tried to understand things like "spanned" "extended" "primary" "swap" "dev/dev2/" "GRUB" "Windows Boot Loader/Manager" etc.... I have a very very limited understanding of all of it! :) I am trying to figure out how to get all OS boot options on one Boot manager (I'm thinking it will be GRUB), because at this point when i turn on my computer, I basically get two booting options (excluding the memtest options etc)... One options is to boot one of my Linux Distros and the second option is to boot my Windows 7. When i go with the first option, Linux boots up... when i go with the second Windows 7 option, I get the "windows boot manager screen" and I can choose Windows 7 or my other installation of Linux (Ubuntu)... In addition, I did not have swap partition from my first installation of Linux, I created it during the installation of my second distro... This is a lot of info for me, but I'm guessing that you linux Gurus, pretty much understand what is going on! Hope my question makes sense.. i will try and simplify... Can i get all 3 OS's optioned to boot from one GRUB? Can i get both Linux distros to use one swap file (I have seen this possible in other threads, but because of how my disk is partitioned, i dont know if i can do this) I hope that i dont have to start all over installing one after the other. Ive got some pics that may help understand my hard drive situation! Thanks guys! :) EDIT... i had some pics, but im a new member.. so cant post them... :( here is a description of the pics... incase i can email them or post later. [grub][3] First Screen I come to after turning on computer... "Ubuntu with linux 3.2.6" (highlighted) fires up Linux perfectly... other choice at bottom of list "Windows 7 (loader) (on dev/sda1)... brings me to the next picture below.. windows boot manager [win boot mngr][6] both options here load the os selected [Disk Manager Windows][1] picture of my hard drive situation through windows disk manager utility [gparted][2] picture of my hard drive situation through "gparted" [mycomp][4] picture of my hard drive situation through "my computer" [paragon][5] one last pic of my hard drive situation through the eyes of "paragon"

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  • Is Spring hard compared to Ruby on Rails?

    - by johnny
    If I have no to little experience in either of them, but know enough Java and Ruby to be comfortable, is one framework harder to learn than the other? Is one easier to use for the beginner on these? I know it is hard to answer. Just looking for general thoughts on it.

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  • MS Access-VBA _ Save a Report to Hard Drive

    - by ledge16
    Hi all, need some help with this code if anyone can answer. Any suggestions are most appreciated. I have a report that I want to save to my hard drive when clicking a button. When saving the report I want the filename to be created using two pieces of information from the report. Variables: Report = "Contract" Save Location = "C:\Folder\" File Name = [Customer] & " _ " & [Date] File Type = PDF Thank you!

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  • BitLocker with Windows DPAPI Encryption Key Management

    - by bigmac
    We have a need to enforce resting encryption on an iSCSI LUN that is accessible from within a Hyper-V virtual machine. We have implementing a working solution using BitLocker, using Windows Server 2012 on a Hyper-V Virtual Server which has iSCSI access to a LUN on our SAN. We were able to successfully do this by using the "floppy disk key storage" hack as defined in THIS POST. However, this method seems "hokey" to me. In my continued research, I found out that the Amazon Corporate IT team published a WHITEPAPER that outlined exactly what I was looking for in a more elegant solution, without the "floppy disk hack". On page 7 of this white paper, they state that they implemented Windows DPAPI Encryption Key Management to securely manage their BitLocker keys. This is exactly what I am looking to do, but they stated that they had to write a script to do this, yet they don't provide the script or even any pointers on how to create one. Does anyone have details on how to create a "script in conjunction with a service and a key-store file protected by the server’s machine account DPAPI key" (as they state in the whitepaper) to manage and auto-unlock BitLocker volumes? Any advice is appreciated.

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  • Ubuntu raid 1 write errors

    - by Micah
    I have an Ubuntu server set up with two SATA drives in a RAID 1 configuration with MDADM. The machine is used to record raw video, which involves a lot of writing to the disk. Sometimes during video recording the computer will crash, will the following errors in kern.log: Mar 15 10:39:41 video kernel: [414501.629864] ata2.00: exception Emask 0x10 SAct 0x0 SErr 0x400100 action 0x6 Mar 15 10:39:41 video kernel: [414501.629870] ata2.00: BMDMA stat 0x26 Mar 15 10:39:41 video kernel: [414501.629875] ata2.00: SError: { UnrecovData Handshk } Mar 15 10:39:41 video kernel: [414501.629880] ata2.00: failed command: WRITE DMA EXT Mar 15 10:39:41 video kernel: [414501.629889] ata2.00: cmd 35/00:00:28:6d:f6/00:04:06:00:00/e0 tag 0 dma 524288 out Mar 15 10:39:41 video kernel: [414501.629891] res 51/84:b1:77:6e:f6/84:02:06:00:00/e0 Emask 0x30 (host bus error) Mar 15 10:39:41 video kernel: [414501.629896] ata2.00: status: { DRDY ERR } Mar 15 10:39:41 video kernel: [414501.629899] ata2.00: error: { ICRC ABRT } Mar 15 10:39:41 video kernel: [414501.629910] ata2.00: hard resetting link Mar 15 10:39:41 video kernel: [414501.973009] ata2.01: hard resetting link Mar 15 10:39:41 video kernel: [414502.482642] ata2.00: SATA link up 3.0 Gbps (SStatus 123 SControl 300) Mar 15 10:39:41 video kernel: [414502.482658] ata2.01: SATA link down (SStatus 0 SControl 300) Mar 15 10:39:41 video kernel: [414502.546160] ata2.00: configured for UDMA/133 Mar 15 10:39:41 video kernel: [414502.546203] ata2: EH complete Is this the result of faulty drives? Is software RAID just not performant enough for data rates ~15 MB/s, even with a quad-core i7? Thanks for your help. Edit: cat /proc/mdstat returns this: Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 sdb1[1] sda1[0] 976760768 blocks [2/2] [UU] unused devices: <none>

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  • Does a 3ware "ECC-ERROR" matter on a JBOD when I have ZFS?

    - by Stefan Lasiewski
    I have a FreeBSD 8.x machine running ZFS and with a 3ware 9690SA controller. The 3ware controller shows an ECC-ERROR with one of the disks: //host> /c0 show VPort Status Unit Size Type Phy Encl-Slot Model ------------------------------------------------------------------------------ p0 OK u0 279.39 GB SAS 0 - SEAGATE ST3300657SS p1 OK u0 279.39 GB SAS 1 - SEAGATE ST3300657SS p2 OK u1 931.51 GB SAS 2 - SEAGATE ST31000640SS p3 ECC-ERROR u2 931.51 GB SAS 3 - SEAGATE ST31000640SS p4 OK u3 931.51 GB SAS 4 - SEAGATE ST31000640SS /c0 show events shows no ECC errors in it's recent history. ZFS does not currently detect any errors. zpool status says No known data errors My question: Is this ECC-ERROR something that I need to be concerned about? According to the 3ware CLI 9.5.2 Manual, an ECC-ERROR means that the 3ware controller caught a read-error for one or more sectors on this drive. This sometimes occurs when a RAID array is recovering from a failed disk. I believe that ECC-ERRORS can also be detected when the 3ware Controller verifies each disk. None of the drives have failed and thus there was no drive rebuild, so I assume that 3ware discovered a bad sector when it ran it's weekly auto-verify scan of the disks. Is this a safe assumption? According to our logs, ZFS has not detected any bad sectors on this drive. ZFS can work around read errors -- if ZFS detects a bad sector on the drive, it will simply mark that sector as bad and never use it again. From the ZFS perspective one bad sector isn't a big deal, although it might indicate that the drive is starting to go bad.

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  • does my machine configuration make sense?

    - by user1227914
    i couldn't think of a better place to ask this question, so here it goes. we're putting together a dedicated server for a website that will initially host the web server and the mysql database. as the website grows, we'll move the database to a different server and this machine will eventually only server the actual website. so the question is ...does my configuration look okay? it's the first time i'm building a server from scratch so i want to make sure i don't combine components that don't fit or something. things like ..do the drives i picked work for the hot swap ..etc. what do you guys think? am i good to go with this configuration? :) Chassis: Supermicro SuperServer 6016T-MTHF (6x DDR3 SDRAM - ECC DIMM 240-pin, 2x LGA1366 Socket, Power Provided: 600 Watt, 4 (free) x hot-swap - 3.5") CPU: Intel BX80614E5620 Xeon E5620 Processor - 4 Core, 2.40GHz, LGA 1366, 5.86GT/s QPI 12MB Cache, 64-Bit, 80W, HyperThreading Memory: Crucial CT51272BB1339 4GB PC10600 DDR3 Memory - 1333MHz, ECC, Registered, 1x4096MB (possibly 3 or 4 of them) Hard Drives: Western Digital WD2002FAEX Caviar Black Hard Drive - 2TB, 3.5", SATA 6Gbps, 7200 RPM, 64MB (possibly 2 or 3). thank you very much for any professional advice :)

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  • How to configure VirtualBox server for performance at home

    - by BluJai
    I currently have two physical Ubuntu Server 10.10 servers at home: one serves as our firewall/router/DHCP/VPN server and the other performs double-duty as a file server and a VirtualBox host for an Ubuntu Desktop 10.10 machine which I use from remote connections (via NoMachine) for many thin-client purposes which are irrelevant to my question. What I'd like to accomplish is to consolidate the two physical machines into one which is a dedicated VirtualBox host (most likely running Ubuntu Server 10.10). Note that I'd like to stick with VirtualBox (if possible) because I'm most comfortable with it and use it on a daily basis at both home and work. Specifically, I plan to have one VM set up as file server, another as the firewall/router/DHCP/VPN (or possibly split those a bit) and a third, which is the only current VM (already VirtualBox), which is the thin-client host. My question comes down to performance and/or recommendations about the file server VM. The file server hosts about 6 terabytes of data across 4 drives. What I'd like to do is use raw disk access from the VM directly to the existing disks. However, I'm curious what performance advantage/disadvantage that would have as compared to using shared folders from the VM host and basically just have the whole drive served as a shared folder to the VM which would then serve it to the other machines on the network. I don't know if virtual disks would even work in this scenario and I certainly wouldn't want a drive to be filled with just a single file which is 1.5 TB (disk image). To add understanding of context, but not to get additional advice, I want to virtualize these machines because I intend to regularly use the snapshot capabilities of VirtualBox for the system disks (which will be virtual drives) of the VMs and I have some physical space/power needs to address (as I mentioned, this is at home).

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  • How to configure VirtualBox server for performance at home

    - by BluJai
    I currently have two physical Ubuntu Server 10.10 servers at home: one serves as our firewall/router/DHCP/VPN server and the other performs double-duty as a file server and a VirtualBox host for an Ubuntu Desktop 10.10 machine which I use from remote connections (via NoMachine) for many thin-client purposes which are irrelevant to my question. What I'd like to accomplish is to consolidate the two physical machines into one which is a dedicated VirtualBox host (most likely running Ubuntu Server 10.10). Note that I'd like to stick with VirtualBox (if possible) because I'm most comfortable with it and use it on a daily basis at both home and work. Specifically, I plan to have one VM set up as file server, another as the firewall/router/DHCP/VPN (or possibly split those a bit) and a third, which is the only current VM (already VirtualBox), which is the thin-client host. My question comes down to performance and/or recommendations about the file server VM. The file server hosts about 6 terabytes of data across 4 drives. What I'd like to do is use raw disk access from the VM directly to the existing disks. However, I'm curious what performance advantage/disadvantage that would have as compared to using shared folders from the VM host and basically just have the whole drive served as a shared folder to the VM which would then serve it to the other machines on the network. I don't know if virtual disks would even work in this scenario and I certainly wouldn't want a drive to be filled with just a single file which is 1.5 TB (disk image). To add understanding of context, but not to get additional advice, I want to virtualize these machines because I intend to regularly use the snapshot capabilities of VirtualBox for the system disks (which will be virtual drives) of the VMs and I have some physical space/power needs to address (as I mentioned, this is at home).

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  • Cannot access drive in Windows 7 after scandisk lockup, but can in safe mode....

    - by Matt Thompson
    I ran scandisk on my external USB drive due to the inability to delete a few files. Windows asked me if I wanted to unmount the drive before the scan, warning me that it would be unusable until the scan was finished, and I said yes. During the scan, my machine locked up, and I was forced to reboot the machine. When it came up, I was unable to access the drive, getting an error that "L:is not accessible, access is denied". Comupter Management sees the drive, and has the proper amount of disk space filled. I booted into safe mode, and can access the drive with no problems, and I noticed that in explorer, all the folders have locks on them. I booted back into windows, but still could not access the drive, getting the same error as above. Hovever, if I right click on the drive, select properties, and go to Customize, in the folder pictures ares, I select Choose File, and a window open up, that shows the root of the directory, with all the folder able to be accessed, but again, the icon is the folder icon with a lock on it. I can even copy files from the drive to another. So, the files are not gone, windows can obviously access the drive no matter what it thinks, so there has to be a problem with the flag windows put on the drive when it ran the original scan that failed. I was able to run a scan both in safe mode with no problems, and in windows. In windows, I received the cannot access error the first time I run scan disk on it, but if I try again, it works fine. Any ideas on how to clear the flag that windows set, so I can access the drive normally again?

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  • Troubleshooting: Monitor never turns on, system fans running, DVD-ROM does not open.

    - by Wesley
    Hi all, Here are my specs beforehand: ECS P4VXASD2+ (V5.0) motherboard FSB 533MHz Intel Pentium 4 2.40A GHz Prescott Socket 478 2x 256MB PC2100 DDR RAM, 2x 256MB PC133 SDRAM CoolMax 350W PSU DVD-ROM - will edit with brand & model 128MB ATi Radeon 9800 Pro AGP No hard drive So, I just put those parts together today and I tried to power it up, with the monitor connected to the Radeon 9800 in the AGP slot (mobo does not have VGA port). After turning it on, the CPU fan, graphics fan and system fan go on. However, the monitor remains in standby mode, despite being plugged in. Also, after pushing the button on the DVD-ROM drive, it does not open. I've used the DVD-ROM drive before with absolutely no issues. The graphics card was slightly buggy when I put it on another machine, which was left outside in winter weather for 3 months. (Still that computer's integrated graphics worked fine.) CMOS battery was replaced and jumpers are all set correctly. Now, I'm wondering whether the motherboard, CPU, PSU or GPU is the problem. What can I do to test which part is the problem? Just to clarify, I don't have a hard drive, so I usually boot Ubuntu from the disc drive. Anyways, thanks in advance!

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  • PC only boots from Linux-based media and won't boot from DOS-based media

    - by Xolstice
    I have this problem where the PC only seems to boot from a floppy disk or CD if it was created as a Linux-based bootable media. If it was created as a DOS-based bootable media the system just freezes at the starting point of the boot process. I originally asked this under question 139515 for CD booting only, and based on the given answers, I was under the impression the problem was with the CD-ROM drive; however, I have since installed a newly purchased CD-ROM drive and the same freezing occurs. This then made me try the DOS bootable floppy disk approach and I was quite surprised that it exhibited the same freezing problem. I then tried try a Linux bootable floppy and everything booted from it without any issues. As I mentioned in my original question, the PC was booting just fine from the DOS-based bootable CD, and then it suddenly decides to pull this freezing stunt. I can't remember if I changed anything in the BIOS settings that may I have caused the problem, but I am wondering if that could be the case - it is currently using the Award Module BIOS v4.60PGMA. Can anyone help?

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  • Quota, AD and C#

    - by Gnial0id
    At first, my mother tongue is not English, so I apologize for the possible mistakes. I'm working on a WS2008R2 server with an Active Directory and a web platform manages this AD with C# code. A group of users have to be able to create user accounts but during the procedure, a disk quota for this new account is (and have to be) created. As the "creator" must not be a member of the Administrators group, the access to the c/: disk is denied. So, I want to perform the File Server Resource Manager operations with C# code by an non-admin account. The code is correct, it works normally with admin account. So, the problem turns around the permissions on the hard drive. I've looked after help on the Internet, without success. It seems that quota delegation is impossible. Only admin can perform this. A colleague helped me a bit, and found the GPO "By pass traverse checking" on a forum but it doesn't seems to be the good way. Any help would be appreciate.

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  • Dell PowerEdge T710, add a new hard disk, how to?

    - by user1340802
    I need to add a new hard disk to a PowerEdge T710 running on Vmware EXSI 4. this hard disk is a 'normal' desktop hard disk 1TB (that is it is not coming from Dell, I also have no rack for it to plug it inside any of the front bay) I would like to add this disk for a virtual machine needing space, the most easily as possible. I have find that there is an avaiable sata cable with its electric power, so may I just add the disk plugging these and using the empty 5"1/4 slot available under the CD drive (with a 5"1/4 - 3"1/2 bay adaptater) ? (even if this way it seems that i bypass the raid controller that own the front bay with racks)) that way i think could be easier than adding the disk to the already defined Raid (btw i am also not sure on how to do these but i would not risk to mess the already working things) what are the other operations that i would have to do to ? (sorry I am a real beginner on Vmware EXSI and PowerEdge management :/ i have seen that there is some management from Bios (CTRL+R as start up) so that the disk will be seen or initialize it. I am really not sure of the steps needed...) thank you, best.

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  • mysql disk io keeps increasing ... is that normal?

    - by trustfundbaby
    So I've been trying to figure out this disk IO problem I have been having with my linode VPS. Over the last day or two I've just left watch -n1 pidstat -d running in a console window and the output looks like this: Monitoring it over the last few days, I've noticed that my problem lies with the init, searchd, and mysql processes. Searchd is sphinx and all its indexes are on disk, so disk io there is inevitable (apparently). What I can't understand is why the disk reads (kB_rd/s) for mysql refuse to stabilize and just keep going up. It started out at 154 yesterday and is up to what you see in that screen shot. but disk writes (kB_wr/s) have remained pretty constant the entire time. My VPS only has 768MB RAM, my mysql db has a size of about 220MB and after running mysqltuner.pl and reading a bit about it, I've been advised to set my innodb_buffer_pool_size to 220MB but I simply cannot afford to do that ... I have it up to 150MB. My question is twofold. Why does the init process have that much disk reading to do? Why is mysql doing so much disk reading?

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  • Recover Data Like a Forensics Expert Using an Ubuntu Live CD

    - by Trevor Bekolay
    There are lots of utilities to recover deleted files, but what if you can’t boot up your computer, or the whole drive has been formatted? We’ll show you some tools that will dig deep and recover the most elusive deleted files, or even whole hard drive partitions. We’ve shown you simple ways to recover accidentally deleted files, even a simple method that can be done from an Ubuntu Live CD, but for hard disks that have been heavily corrupted, those methods aren’t going to cut it. In this article, we’ll examine four tools that can recover data from the most messed up hard drives, regardless of whether they were formatted for a Windows, Linux, or Mac computer, or even if the partition table is wiped out entirely. Note: These tools cannot recover data that has been overwritten on a hard disk. Whether a deleted file has been overwritten depends on many factors – the quicker you realize that you want to recover a file, the more likely you will be able to do so. Our setup To show these tools, we’ve set up a small 1 GB hard drive, with half of the space partitioned as ext2, a file system used in Linux, and half the space partitioned as FAT32, a file system used in older Windows systems. We stored ten random pictures on each hard drive. We then wiped the partition table from the hard drive by deleting the partitions in GParted. Is our data lost forever? Installing the tools All of the tools we’re going to use are in Ubuntu’s universe repository. To enable the repository, open Synaptic Package Manager by clicking on System in the top-left, then Administration > Synaptic Package Manager. Click on Settings > Repositories and add a check in the box labelled “Community-maintained Open Source software (universe)”. Click Close, and then in the main Synaptic Package Manager window, click the Reload button. Once the package list has reloaded, and the search index rebuilt, search for and mark for installation one or all of the following packages: testdisk, foremost, and scalpel. Testdisk includes TestDisk, which can recover lost partitions and repair boot sectors, and PhotoRec, which can recover many different types of files from tons of different file systems. Foremost, originally developed by the US Air Force Office of Special Investigations, recovers files based on their headers and other internal structures. Foremost operates on hard drives or drive image files generated by various tools. Finally, scalpel performs the same functions as foremost, but is focused on enhanced performance and lower memory usage. Scalpel may run better if you have an older machine with less RAM. Recover hard drive partitions If you can’t mount your hard drive, then its partition table might be corrupted. Before you start trying to recover your important files, it may be possible to recover one or more partitions on your drive, recovering all of your files with one step. Testdisk is the tool for the job. Start it by opening a terminal (Applications > Accessories > Terminal) and typing in: sudo testdisk If you’d like, you can create a log file, though it won’t affect how much data you recover. Once you make your choice, you’re greeted with a list of the storage media on your machine. You should be able to identify the hard drive you want to recover partitions from by its size and label. TestDisk asks you select the type of partition table to search for. In most cases (ext2/3, NTFS, FAT32, etc.) you should select Intel and press Enter. Highlight Analyse and press enter. In our case, our small hard drive has previously been formatted as NTFS. Amazingly, TestDisk finds this partition, though it is unable to recover it. It also finds the two partitions we just deleted. We are able to change their attributes, or add more partitions, but we’ll just recover them by pressing Enter. If TestDisk hasn’t found all of your partitions, you can try doing a deeper search by selecting that option with the left and right arrow keys. We only had these two partitions, so we’ll recover them by selecting Write and pressing Enter. Testdisk informs us that we will have to reboot. Note: If your Ubuntu Live CD is not persistent, then when you reboot you will have to reinstall any tools that you installed earlier. After restarting, both of our partitions are back to their original states, pictures and all. Recover files of certain types For the following examples, we deleted the 10 pictures from both partitions and then reformatted them. PhotoRec Of the three tools we’ll show, PhotoRec is the most user-friendly, despite being a console-based utility. To start recovering files, open a terminal (Applications > Accessories > Terminal) and type in: sudo photorec To begin, you are asked to select a storage device to search. You should be able to identify the right device by its size and label. Select the right device, and then hit Enter. PhotoRec asks you select the type of partition to search. In most cases (ext2/3, NTFS, FAT, etc.) you should select Intel and press Enter. You are given a list of the partitions on your selected hard drive. If you want to recover all of the files on a partition, then select Search and hit enter. However, this process can be very slow, and in our case we only want to search for pictures files, so instead we use the right arrow key to select File Opt and press Enter. PhotoRec can recover many different types of files, and deselecting each one would take a long time. Instead, we press “s” to clear all of the selections, and then find the appropriate file types – jpg, gif, and png – and select them by pressing the right arrow key. Once we’ve selected these three, we press “b” to save these selections. Press enter to return to the list of hard drive partitions. We want to search both of our partitions, so we highlight “No partition” and “Search” and then press Enter. PhotoRec prompts for a location to store the recovered files. If you have a different healthy hard drive, then we recommend storing the recovered files there. Since we’re not recovering very much, we’ll store it on the Ubuntu Live CD’s desktop. Note: Do not recover files to the hard drive you’re recovering from. PhotoRec is able to recover the 20 pictures from the partitions on our hard drive! A quick look in the recup_dir.1 directory that it creates confirms that PhotoRec has recovered all of our pictures, save for the file names. Foremost Foremost is a command-line program with no interactive interface like PhotoRec, but offers a number of command-line options to get as much data out of your had drive as possible. For a full list of options that can be tweaked via the command line, open up a terminal (Applications > Accessories > Terminal) and type in: foremost –h In our case, the command line options that we are going to use are: -t, a comma-separated list of types of files to search for. In our case, this is “jpeg,png,gif”. -v, enabling verbose-mode, giving us more information about what foremost is doing. -o, the output folder to store recovered files in. In our case, we created a directory called “foremost” on the desktop. -i, the input that will be searched for files. This can be a disk image in several different formats; however, we will use a hard disk, /dev/sda. Our foremost invocation is: sudo foremost –t jpeg,png,gif –o foremost –v –i /dev/sda Your invocation will differ depending on what you’re searching for and where you’re searching for it. Foremost is able to recover 17 of the 20 files stored on the hard drive. Looking at the files, we can confirm that these files were recovered relatively well, though we can see some errors in the thumbnail for 00622449.jpg. Part of this may be due to the ext2 filesystem. Foremost recommends using the –d command-line option for Linux file systems like ext2. We’ll run foremost again, adding the –d command-line option to our foremost invocation: sudo foremost –t jpeg,png,gif –d –o foremost –v –i /dev/sda This time, foremost is able to recover all 20 images! A final look at the pictures reveals that the pictures were recovered with no problems. Scalpel Scalpel is another powerful program that, like Foremost, is heavily configurable. Unlike Foremost, Scalpel requires you to edit a configuration file before attempting any data recovery. Any text editor will do, but we’ll use gedit to change the configuration file. In a terminal window (Applications > Accessories > Terminal), type in: sudo gedit /etc/scalpel/scalpel.conf scalpel.conf contains information about a number of different file types. Scroll through this file and uncomment lines that start with a file type that you want to recover (i.e. remove the “#” character at the start of those lines). Save the file and close it. Return to the terminal window. Scalpel also has a ton of command-line options that can help you search quickly and effectively; however, we’ll just define the input device (/dev/sda) and the output folder (a folder called “scalpel” that we created on the desktop). Our invocation is: sudo scalpel /dev/sda –o scalpel Scalpel is able to recover 18 of our 20 files. A quick look at the files scalpel recovered reveals that most of our files were recovered successfully, though there were some problems (e.g. 00000012.jpg). Conclusion In our quick toy example, TestDisk was able to recover two deleted partitions, and PhotoRec and Foremost were able to recover all 20 deleted images. Scalpel recovered most of the files, but it’s very likely that playing with the command-line options for scalpel would have enabled us to recover all 20 images. These tools are lifesavers when something goes wrong with your hard drive. If your data is on the hard drive somewhere, then one of these tools will track it down! 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  • how can I fix error: hd0 out of disk?

    - by rux
    I am running Ubuntu 12.04 on a netbook - Acer AS 1410. After a download session, I restarted the computer and it said: error: hd0 out of disk. Press any key to continue... I pressed everything, but it's just frozen there. Any idea what's wrong with it and what I can do to fix it? I haven't been able to run my computer at all since it's frozen like that. Help please! I booted the live cd and ran sudo fdisk -lu into terminal, and here's what it gave me: Disk /dev/sda: 60.0 GB, 60022480896 bytes 255 heads, 63 sectors/track, 7297 cylinders, total 117231408 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x9a696263 Device Boot Start End Blocks Id System /dev/sda3 2048 117229567 58613760 5 Extended /dev/sda5 * 71647232 109039615 18696192 83 Linux /dev/sda6 109041664 117229567 4093952 82 Linux swap / Solaris /dev/sda7 4096 71645183 35820544 83 Linux Partition table entries are not in disk order I am somewhat of a beginner in this, so don't know what this means. any ideas? Thanks!

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