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  • Causes of sudden massive filesystem damage? ("root inode is not a directory")

    - by poolie
    I have a laptop running Maverick (very happily until yesterday), with a Patriot Torx SSD; LUKS encryption of the whole partition; one lvm physical volume on top of that; then home and root in ext4 logical volumes on top of that. When I tried to boot it yesterday, it complained that it couldn't mount the root filesystem. Running fsck, basically every inode seems to be wrong. Both home and root filesystems show similar problems. Checking a backup superblock doesn't help. e2fsck 1.41.12 (17-May-2010) lithe_root was not cleanly unmounted, check forced. Resize inode not valid. Recreate? no Pass 1: Checking inodes, blocks, and sizes Root inode is not a directory. Clear? no Root inode has dtime set (probably due to old mke2fs). Fix? no Inode 2 is in use, but has dtime set. Fix? no Inode 2 has a extra size (4730) which is invalid Fix? no Inode 2 has compression flag set on filesystem without compression support. Clear? no Inode 2 has INDEX_FL flag set but is not a directory. Clear HTree index? no HTREE directory inode 2 has an invalid root node. Clear HTree index? no Inode 2, i_size is 9581392125871137995, should be 0. Fix? no Inode 2, i_blocks is 40456527802719, should be 0. Fix? no Reserved inode 3 (<The ACL index inode>) has invalid mode. Clear? no Inode 3 has compression flag set on filesystem without compression support. Clear? no Inode 3 has INDEX_FL flag set but is not a directory. Clear HTree index? no .... Running strings across the filesystems, I can see there are what look like filenames and user data there. I do have sufficiently good backups (touch wood) that it's not worth grovelling around to pull back individual files, though I might save an image of the unencrypted disk before I rebuild, just in case. smartctl doesn't show any errors, neither does the kernel log. Running a write-mode badblocks across the swap lv doesn't find problems either. So the disk may be failing, but not in an obvious way. At this point I'm basically, as they say, fscked? Back to reinstalling, perhaps running badblocks over the disk, then restoring from backup? There doesn't even seem to be enough data to file a meaningful bug... I don't recall that this machine crashed last time I used it. At this point I suspect a bug or memory corruption caused it to write garbage across the disks when it was last running, or some kind of subtle failure mode for the SSD. What do you think would have caused this? Is there anything else you'd try?

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  • How to delete files and folders that cannot be deleted?

    - by glenneroo
    I have a backup copy of a previous Windows' Documents and Settings folder which only contains my original user and within 2 more directories: Favorites and Local Settings. When I try to delete Local Settings I get this error: When I try to delete Favorites, I get this error: I ran this in a cmd shell: attrib *.* -r -a -s -h /s ...but it did not help, nor did it return any errors/warnings. I used Unlocker v1.8.5 and LockHunter repeatedly at multiple levels to see if any files are in use, but both always say: No Files Locked. Update #1: I was able to rename the directory, which now gives me this warning before (trying to) delete: If I press Yes (or Yes to All) then I get this error: Update #2: I let chkdsk /f run which required a reboot since it's on my primary system partition. During Stage 2 scanning, I received about 40 of these: Deleting an index entry from index $0 of file 25. ...followed by: Deleting index entry cookies in index $I30 of file 37576. ...but I still get the first error dialog above when trying to delete. I ran chkdsk again, this time: chkdsk /f /r. Produced no messages. Same result when deleting. Update #3: Digging deeper, the 99 is the name of one of many directories located deep in here: C:\Documents and Settings.OLD\User\Local Settings\Application Data\Microsoft\Messenger\[email protected]\SharingMetadata\[email protected]\DFSR\Staging\CS{D4E4AE55-B5E2-F03B-5189-6C4DA6E41788}\ Inside each of those directories were files with names such as: 2300-{C93D01AC-0739-4FD9-88C7-13D2F21A208E}-v2300-{C93D01AC-0739-4FD9-88C7-13D2F21A208E}-v2300-Downloaded.frx I noticed that, unlike all the directories, I couldn't rename any of these files. I also noticed that the file + dir names were extremely long: Original directory = 194 characters Filenames = 100+ characters Together the length exceeds the 255-char limit which is bad and would explain the error message I posted in Update #1. Partial Solution: Rename all directories until the total path length is less than 100. Afterwards I was able to rename the .frx files, not to mention delete everything inside the Local Settings directory. This is only a partial solution because these (empty) directories are still not deleteable, C:\1\2\Favorites\Wien\What To Do.. C:\1\2\Favorites\Photography\FIRE Same error as above: Here is what Explorer properties shows for both folders: Update #4 (another partial solution): Using harrymc's answer combined with thoroughly reading through this amazing MS-KB article which contains nearly everyone's idea and then some, inconspicuously titled: You cannot delete a file or a folder on an NTFS file system volume. I was able to delete the 2nd folder C:\1\2\Favorites\Photography\FIRE - the problem being that there was an invisible trailing space at the end. I got lucky when I did an auto-complete whilst playing around with the del "\\?\<path>" command which he suggested. NOTE: A normal del did NOT work, nor did deleting from explorer. Now all that is left is the first directory C:\1\2\Favorites\Wien\What To Do.. (yes I tried endlessly with multiple combinations of the above solution ;) Keep 'em coming! =)

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  • How to use more than 3 virtual disks in Linux using CentOS and XenServer

    - by 010110110101
    I've attached 5 virtual disks to a Virtual Machine in Citrix XenServer. The VM has the xs-tools installed. Initially it said that it couldn't add so many disks. After I installed the xs-tools, it let me add all the disks. But /dev doesn't show all the disks. It shows these: /dev/xvda /dev/xvdb /dev/xvdc /dev/cdrom Perhaps it is bound by the limits of an IDE bus? (3 disks + CD-ROM) If so, how does one change the VM to use SCSI? Edit: According to the documentation: 2.6.3. VM Block Devices In the PV Linux case, block devices are passed through as PV devices. XenServer does not attempt to emulate SCSI or IDE, but instead provides a more suitable interface in the virtual environment in the form of xvd* devices. It is also possible to get an sd* device using the same mechanism, where the PV driver inside the VM takes over the SCSI device namespace. This is not desirable so it is best to use xvd* where possible for PV guests (this is the default for Debian and RHEL). For Windows or other fully virtualized guests, XenServer emulates an IDE bus in the form of an hd* device. When using Windows, installing the Citrix Tools for Virtual Machines installs a special PV driver that works in a similar way to Linux, except in the fully virtualized environment. Still, with 5 virtual disks attached, I don't see the other xvd devices. Edit #2: (attached requested info) Host Machine: XenServer 6.1 Linux version 2.6.32.43-0.4.1.xs1.6.10.777.170770xen (geeko@buildhost) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-51)) #1 SMP Wed Apr 17 05:52:03 EDT 2013 Guest Machine: CentOS release 6.4 (Final) Linux version 2.6.32-358.6.2.el6.x86_64 ([email protected]) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-3) (GCC) ) #1 SMP Thu May 16 20:59:36 UTC 2013 Output of 'fdisk -l' on Guest Machine: Note, the disk beyond the first 3 attached are not displaying -- there should be 4 100GB disks. (There are a total of 5 disks displayed in XenCenter -- 16GB, 100GB, 100GB, 100GB, 100GB) Disk /dev/xvdb: 107.4 GB, 107374182400 bytes 255 heads, 63 sectors/track, 13054 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xfb6c95b9 Device Boot Start End Blocks Id System /dev/xvdb1 1 13054 104856223+ 83 Linux Disk /dev/xvda: 17.2 GB, 17179869184 bytes 255 heads, 63 sectors/track, 2088 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000e5f41 Device Boot Start End Blocks Id System /dev/xvda1 * 1 64 512000 83 Linux Partition 1 does not end on cylinder boundary. /dev/xvda2 64 2089 16264192 8e Linux LVM Disk /dev/xvdc: 107.4 GB, 107374182400 bytes 255 heads, 63 sectors/track, 13054 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xed249ced Device Boot Start End Blocks Id System /dev/xvdc1 1 13054 104856223+ 83 Linux Disk /dev/mapper/vg_blue-lv_root: 14.6 GB, 14571012096 bytes 255 heads, 63 sectors/track, 1771 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/vg_blue-lv_swap: 2080 MB, 2080374784 bytes 255 heads, 63 sectors/track, 252 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 I see that the Linux versions say SMP. The Guest VM doesn't say "xen" in the name. However, I have already run yum install kernel-xen. Could be a clue?

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  • File copying utility like rsync with error handling like ddrescue, for data recovery from a hard drive with bad sectors or hardware failure

    - by purefusion
    I have a hard drive with either bad blocks or sectors that are failing to read due to potential mechanical issues, such as a bad disk head, bad motor, or some other issue that is causing the hard drive to read data excruciatingly slowly and with lots of read errors. I'm seeing an average of 50 KB/sec, with some reads dropping below 10 KB/sec, and frequently it gets stuck on a file or sector altogether, usually for quite a long time—from 2-10 minutes or more (when using rsync, before it times out). Speed seems to vary wildly, and it gets stuck on files a lot, and when it finally gets "unstuck" it only seems to last for a short burst before it gets stuck again. The drive is also very quiet with only an occasional sound of files copying (usually when it gets stuck/unstuck for a brief time, before getting stuck again). Thus, there are none of those evil sounds that are normally associated with HDD death. Someone suggested that the problems sounded like they might be caused by a misaligned disk head, which requires a lot of re-reads before it finally reads data with success. Sounds plausible, but I digress... Anyway, the problem with rsync is that it seems to have no decent error handling support. Obviously, it wasn't meant for use in recovering data from failing hard drives, but all the so-called "data recovery" utilities out there that are meant for such use usually focus on recovery of deleted files or messed up partitions, rather than copying files off dying hard drives. Deleted file recovery is not what I need, obviously, so perhaps you can understand my disappointment in not being able to find what I'm after yet. Naturally, this is where you'd probably say "You should use ddrescue!" Well, that's all fine and dandy, but I've already got most of the data backed up, so I just want to recover certain files. I'm not concerned with trying to recover a full partition block-by-block as ddrescue does. I am only interested in rescuing just specific files and directories. Ideally, what I'd like is some sort of cross between rsync and ddrescue: something that lets me specify source and destination as directories of normal files like rsync (rather than two full partitions as ddrescue requires), with a way to skip files with errors in an initial run, and then allows me to attempt recovery of those files with errors in a later run (with a slightly altered command, of course), perhaps even offering an option to specify the number of retry attempts ...just like how ddrescue works with blocks, only I want a utility that works with specific files/directories like rsync does. So am I daydreaming here, or does something out there exist that can do this? Or, maybe even a way to make rsync or ddrescue work in such a way? I'm really open to whatever solutions might work, so long as they let me choose which files I want to "rescue", and can skip files with errors in the initial run, and try/retry those errors again later. So far I've tried rsync with the following options, but it often gets stuck on a file for longer than the timeout, and ideally I'd just like it to move on to the next file and come back later to the files it gets stuck on. I don't think that's possible though. Anyway, here's what I've been using up till now: rsync -avP --stats --block-size=512 --timeout=600 /path/to/source/* /path/to/destination/

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  • Using different SSDs types (not only SATA based) as system drive

    - by Hubert Kario
    Currently I have a Thinkpad X61s and want to make it both a bit faster and a bit more power efficient. For that reason I thought that adding SSD drive would make most sense. Unfortunately, because of financial reasons, buying SSD of over 200GB capacity is out of reach for me (not only it would be worth more than the rest of the laptop, but also I currently have a 500GB drive in it, so even such a drive would be kind of a downgrade for me). During preliminary testing with a cheap Transcend 4GB Class 6 (14MiB/s streaming, 9MiB/s random read) card I experienced boot times to be reduced by half so putting the OS only on it would already would be an improvement. Unfortunately, my system now is about 11GiB in size so anything less than 16GB would be constraining. In this laptop I can connect additional drives on at least 5 different ways: using SATA-ATA converter caddy in the X6 Ultrabase using internal mini PCIe slot using integrated SDHC slot using CardBus (a.k.a PCMCIA or PC Card) slot using USB Thankfully, because I use only Linux on this PC the bootability of them is irrelevant as I can put the /boot partition on internal HDD and / on any of the above mentioned Flash memories (as I already did for the SDHC test). From what I was able to research and from my own experience those options come with rather big downsides or other problems: SATA-ATA caddy It has three downsides: I have to carry the Ultrabse with me at all times (it's not really inconvenient, but those grams do add) and couldn't disconnect it when I want to disconnect the battery It makes the bay unusable for the optical drive and occasional quick access to other hard drives the only caddies I could buy have rather flaky controllers in them so putting my OS on it would hamper its stability Internal mini PCIe slot This would be an ideal solution, if only I could find real PCIe SSDs, not only devices that could talk only SATA or ATA over PCIe mechanical connection (the ones used in Dell Mini or Asus EEE). Theoretically Samsung did release such devices but I couldn't find them in retail anywhere. Integrated SDHC slot It's a nice solution with a single drawback: the fastest 16GB SDHC card on the market can only do around 35MiB/s read and 15MiB/s write while still costing like a normal 40GB SATA SSD that's 10 times faster. Not really cost-effective. CardBus (a.k.a PCMCIA or PC Card) slot Those cards are much faster than the SDHC option (there are ones that can do well over 50MiB/s read in benchmarks) and from what I could find the PCMCIA controller in my laptop does support UDMA so it should be able to deliver comparable speeds. They still cost similarly to SD cards but at least they provide streaming performance comparable to my current HDD. USB That's the worst option. Not only is it limited to 20-30MiB/s by the interface itself the drive would stick out of the laptop so it's a big no no. The question As such I think that going the "CF in a CardBus adapter" route will be the best option. My question is: did anyone try using CF cards in CardBus adapters as system drives with Linux on Thinkpad laptops? Laptops in general? What was the real-world performance? I don't have any CF cards so I can't check how well does it work with suspend/resume, or whatever it's easy to make it work in initramfs (I'm using ArchLinux and SD card was trivial — add 3 modules in single config line and rebuilding initramfs) so any tips/gotchas on this are welcome as well.

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  • Do hard drive enclosures fail/is it the HDD or enclosure?

    - by x0a
    I'm having a whole host of problems with an external hard drive that was working just fine a couple of hours ago. I've had this problem before once, and that was about 3 months ago, here's what I documented: So a couple of hours ago I turned off all my computers and shut off the power to all my devices in my room, then went and turned the power off at the main switch so I could change an outlet. A couple hours later, after I've already slowly turned everything back on, I go to my xbox to try and watch a movie and it can't seem to list any of the movies I've got. So I go to my desktop to find that my external hard drive isn't there.. even though it's on and connected. It's also stationary and hidden behind something so there's not a whole lot of tampering/physical wear to that external. I plug it into my laptop to try and see what's going on. It starts making this endless loud screeching noise. None of that clicking that's usually associated with hd damage. It's not listed in my computers, and it shows up in Disk Management as "uninitialized" asking me to choose between two different partition types. After carefully disconnecting it and connecting it back, it asks me to format it, which I cancel. I start googling about my issue, starting to accept the situation, torn as hell and helpless and just about ready to toss the thing. Suddenly the screeching stops, after almost 45 minutes of it going, and Disk Management lists the drive as "Online" and "Healthy". Explorer pops up with all my files! I'm still being really careful with it and weary and treating it as though it's in fragile shape. I've downloaded some S.M.A.R.T. software to read the values and everything is listed as "OK" . No reallocated sectors, no read errors, no seek errors. I also ran a quick self-test, which completed without error. Everything seems fine. It looks to be a perfectly healthy external hard drive. So what the hell was that about? Was it doing some sort of maintenance or self-test? How am I supposed to tell the difference? I would've undoubtedly killed the drive for sure if had it gone on a bit longer. I've got the same problem now, with one exception: it doesn't magically reappear after the screeching stops. Occasionally I manage to get some S.M.A.R.T. diagnostics information, which basically reads everything as fine. The only problem is that my HD isn't initializing (so I can't access anything in it). I'm able to successfully run a quick smart test but not an extended one (I've only tried it once but got conflicting indications as to whether it was actually making any progress or not (was stuck on Random read test). So, final question (if all else fails): Could the hard drive enclosure be failing rather than the HDD? Is this a likely possibility at all? How would I know?

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  • How can I recover an ext4 filesystem corrupted after a fsck?

    - by Regan
    I have an ext4 filesystem on luks over software raid5. The filesystem was operating "just fine" for several years when I was beginning to run out of space. I had a 9T volume on 6x2T drives. I began upgrading to 3T drives by doing the mdadm fail, remove, add, rebuild, repeat process until I had a larger array. I then grew the luks container, and then when I unmounted and tried to resize2fs I was given the message the filesystem was dirty and needed e2fsck. Without thinking I just did e2fsck -y /dev/mapper/candybox and it began spewing all kinds of inode being removed type messages (can't remember exactly) I killed e2fsck and tried to remount the filesystem to backup data I was concerned about. When trying to mount at this point I get: # mount /dev/mapper/candybox /candybox mount: wrong fs type, bad option, bad superblock on /dev/mapper/candybox, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so Looking back at my older logs I noticed the filesystem was giving this error each time the machine booted: kernel: [79137.275531] EXT4-fs (dm-2): warning: mounting fs with errors, running e2fsck is recommended So shame on me for not paying attention :( I then tried to mount using every backup superblock (one after another) and each attempt left this in my log: EXT4-fs (dm-2): ext4_check_descriptors: Checksum for group 0 failed (26534!=65440) EXT4-fs (dm-2): ext4_check_descriptors: Checksum for group 1 failed (38021!=36729) EXT4-fs (dm-2): ext4_check_descriptors: Checksum for group 2 failed (18336!=39845) ... EXT4-fs (dm-2): ext4_check_descriptors: Checksum for group 11911 failed (28743!=44098) BUG: soft lockup - CPU#0 stuck for 23s! [mount:2939] Attempts to restart e2fsck results in: # e2fsck /dev/mapper/candybox e2fsck 1.41.14 (22-Dec-2010) e2fsck: Group descriptors look bad... trying backup blocks... candy: recovering journal e2fsck: unable to set superblock flags on candy At this point, I decided it best to order some more drives and make an image using ddrescue Now two weeks later I have an image of the luks partition in a .img file. # ls -lh total 14T -rw-r--r-- 1 root root 14T Oct 25 01:57 candybox.img -rw-r--r-- 1 root root 271 Oct 20 14:32 candybox.logfile After numerous attempts using everything I could find online I could not coerce e2fsck to do anything on the image, so I used mkfs.ext4 -L candy candybox.img -m 0 -S and I was able to mount the dirty filesystem readonly without the journal and recover 960G of data. It gave all kinds of errors of various directories not existing and so forth but I was able to get some stuff. Which gave me some hope! I then ran e2fsck again and it had to recreate the root inode and gave a massive list of correcting group counts, I accepted the root inode creation and said no to everything else, leaving a completely empty filesystem. Re-ran again and said yes to all questions with the same result but now a "clean" but empty filesystem. extundelete gives me 0 recoverable inodes found. And now I'm stuck again, I can't come up with any other methods other than dropping to something like photorec which will give me an absolute mess with how large the filesystem was. I'm willing to re-copy the image from the original array and start over, if I can get any suggestions or ideas on a way to get more of my files back. I wish I could give more detailed logs of the commands that have run, but the output is long scrolled passed except for what gets logged to syslog and my memory is not as detailed due to the timeframe this has occurred over. Any help is greatly appreciated!

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  • I am starting to think that Prevx.com isnt a legit site...but heres my long-winded question

    - by cop1152
    I apologize in advance for the long-winded post. I posted it all because I believe its informative and may be useful. Also, I posted my question at the end. Moments ago I was RDC to a file server in my home (from inside my home). I had opened Firefox and Googled for a manufacturers website. Immediately after clicking the link, Firefox abruptly closed. This seemed odd to me to so I checked the running processes and discovered d.exe, e.exe, and f.exe running. I Googled these processes on a different machine and found them belonging to a key-logger/screen-capturer/trojan called defender.exe, which according to the Prevx lives in c:\documents and settings\user\local settings\temp. (Prevx link http://www.prevx.com/filenames/147352809685142526-X1/DEFENDER32.EXE.html) Simultaneously, an obviously-spoofed Windows Firewall popup appeared on the server asking me to click ‘yes’ to update Windows Firewall. At this time I ended all rogue processes, emptied the temp folder, removed defender.exe from startup, and checked my registry and a few other locations. Before deleting Defender.exe I noted that it was created moments ago, just before Firefox crashed. I believe that I was ‘almost’ infected with this malware. I believe that it needed me to click the phony popup in order to complete infection because it wasn’t allowed to execute processes from the temp folder. After cleaning the machine, I restarted it and have been monitoring it for over an hour. I am debating on whether or not to restore the Windows partition (a separate physical drive from the data) or to just watch it for awhle. I should mention that, because of the specs on this machine, I do not run antivirus software, but I know it well and inspect it regularly. It is a very old Compaq with a 400mhz processer and 512mb of ram. I have a static IP and the server is in the DMZ running an FTP client and some HTTP server software. All files transferred to and stored on this machine are scanned for malware before transferring. Usually the machine only runs 19 processes and performs pretty well for its intended purpose. I posted the story so that you could be aware of a possible new piece of malware and how it acts, but I also have a question or two. First, over the last few months I have noticed that PREVX is listed at the top of most of my Google searches when researching malware, especially for new or obscure malware…and they always want you to purchase something. I don’t think they are one of the top AV companies, so it seems odd that they are always the top Google result. Does anyone have any experience with any of their products? Also, what sites do you rely on for malware researching? Recently, I have found it difficult to find good info because of HijackThis-logs and other deadend info cluttering up my searches. And lastly, besides antivirus, third-party firewall, etc, what settings would you use to lock down a machine to make it more secure in instances where a stubborn admin like myself refuses to run AV? Thanks.

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  • linux raid 1: right after replacing and syncing one drive, the other disk fails - understanding what is going on with mdstat/mdadm

    - by devicerandom
    We have an old RAID 1 Linux server (Ubuntu Lucid 10.04), with four partitions. A few days ago /dev/sdb failed, and today we noticed /dev/sda had pre-failure ominous SMART signs (~4000 reallocated sector count). We replaced /dev/sdb this morning and rebuilt the RAID on the new drive, following this guide: http://www.howtoforge.com/replacing_hard_disks_in_a_raid1_array Everything went smooth until the very end. When it looked like it was finishing to synchronize the last partition, the other old one failed. At this point I am very unsure of the state of the system. Everything seems working and the files seem to be all accessible, just as if it synchronized everything, but I'm new to RAID and I'm worried about what is going on. The /proc/mdstat output is: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md3 : active raid1 sdb4[2](S) sda4[0] 478713792 blocks [2/1] [U_] md2 : active raid1 sdb3[1] sda3[2](F) 244140992 blocks [2/1] [_U] md1 : active raid1 sdb2[1] sda2[2](F) 244140992 blocks [2/1] [_U] md0 : active raid1 sdb1[1] sda1[2](F) 9764800 blocks [2/1] [_U] unused devices: <none> The order of [_U] vs [U_]. Why aren't they consistent along all the array? Is the first U /dev/sda or /dev/sdb? (I tried looking on the web for this trivial information but I found no explicit indication) If I read correctly for md0, [_U] should be /dev/sda1 (down) and /dev/sdb1 (up). But if /dev/sda has failed, how can it be the opposite for md3 ? I understand /dev/sdb4 is now spare because probably it failed to synchronize it 100%, but why does it show /dev/sda4 as up? Shouldn't it be [__]? Or [_U] anyway? The /dev/sda drive now cannot even be accessed by SMART anymore apparently, so I wouldn't expect it to be up. What is wrong with my interpretation of the output? I attach also the outputs of mdadm --detail for the four partitions: /dev/md0: Version : 00.90 Creation Time : Fri Jan 21 18:43:07 2011 Raid Level : raid1 Array Size : 9764800 (9.31 GiB 10.00 GB) Used Dev Size : 9764800 (9.31 GiB 10.00 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 0 Persistence : Superblock is persistent Update Time : Tue Nov 5 17:27:33 2013 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 1 Spare Devices : 0 UUID : a3b4dbbd:859bf7f2:bde36644:fcef85e2 Events : 0.7704 Number Major Minor RaidDevice State 0 0 0 0 removed 1 8 17 1 active sync /dev/sdb1 2 8 1 - faulty spare /dev/sda1 /dev/md1: Version : 00.90 Creation Time : Fri Jan 21 18:43:15 2011 Raid Level : raid1 Array Size : 244140992 (232.83 GiB 250.00 GB) Used Dev Size : 244140992 (232.83 GiB 250.00 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 1 Persistence : Superblock is persistent Update Time : Tue Nov 5 17:39:06 2013 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 1 Spare Devices : 0 UUID : 8bcd5765:90dc93d5:cc70849c:224ced45 Events : 0.1508280 Number Major Minor RaidDevice State 0 0 0 0 removed 1 8 18 1 active sync /dev/sdb2 2 8 2 - faulty spare /dev/sda2 /dev/md2: Version : 00.90 Creation Time : Fri Jan 21 18:43:19 2011 Raid Level : raid1 Array Size : 244140992 (232.83 GiB 250.00 GB) Used Dev Size : 244140992 (232.83 GiB 250.00 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 2 Persistence : Superblock is persistent Update Time : Tue Nov 5 17:46:44 2013 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 1 Spare Devices : 0 UUID : 2885668b:881cafed:b8275ae8:16bc7171 Events : 0.2289636 Number Major Minor RaidDevice State 0 0 0 0 removed 1 8 19 1 active sync /dev/sdb3 2 8 3 - faulty spare /dev/sda3 /dev/md3: Version : 00.90 Creation Time : Fri Jan 21 18:43:22 2011 Raid Level : raid1 Array Size : 478713792 (456.54 GiB 490.20 GB) Used Dev Size : 478713792 (456.54 GiB 490.20 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 3 Persistence : Superblock is persistent Update Time : Tue Nov 5 17:19:20 2013 State : clean, degraded Active Devices : 1 Working Devices : 2 Failed Devices : 0 Spare Devices : 1 Number Major Minor RaidDevice State 0 8 4 0 active sync /dev/sda4 1 0 0 1 removed 2 8 20 - spare /dev/sdb4 The active sync on /dev/sda4 baffles me. I am worried because if tomorrow morning I have to replace /dev/sda, I want to be sure what should I sync with what and what is going on. I am also quite baffled by the fact /dev/sda decided to fail exactly when the raid finished resyncing. I'd like to understand what is really happening. Thanks a lot for your patience and help. Massimo

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  • use svcutil to map multiple namespaces for generating wcf service proxies

    - by Pratik
    I want to use svcutil to map multiple wsdl namespace to clr namespace when generating service proxies. I use strong versioning of namespaces and hence the generated clr namespaces are awkward and may mean many client side code changes if the wsdl/xsd namespace version changes. A code example would be better to show what I want. // Service code namespace TestService.StoreService { [DataContract(Namespace = "http://mydomain.com/xsd/Model/Store/2009/07/01")] public class Address { [DataMember(IsRequired = true, Order = 0)] public string street { get; set; } } [ServiceContract(Namespace = "http://mydomain.com/wsdl/StoreService-v1.0")] public interface IStoreService { [OperationContract] List<Customer> GetAllCustomersForStore(int storeId); [OperationContract] Address GetStoreAddress(int storeId); } public class StoreService : IStoreService { public List<Customer> GetAllCustomersForStore(int storeId) { throw new NotImplementedException(); } public Address GetStoreAddress(int storeId) { throw new NotImplementedException(); } } } namespace TestService.CustomerService { [DataContract(Namespace = "http://mydomain.com/xsd/Model/Customer/2009/07/01")] public class Address { [DataMember(IsRequired = true, Order = 0)] public string city { get; set; } } [ServiceContract(Namespace = "http://mydomain.com/wsdl/CustomerService-v1.0")] public interface ICustomerService { [OperationContract] Customer GetCustomer(int customerId); [OperationContract] Address GetStoreAddress(int customerId); } public class CustomerService : ICustomerService { public Customer GetCustomer(int customerId) { throw new NotImplementedException(); } public Address GetStoreAddress(int customerId) { throw new NotImplementedException(); } } } namespace TestService.Shared { [DataContract(Namespace = "http://mydomain.com/xsd/Model/Shared/2009/07/01")] public class Customer { [DataMember(IsRequired = true, Order = 0)] public int CustomerId { get; set; } [DataMember(IsRequired = true, Order = 1)] public string FirstName { get; set; } } } 1. svcutil - without namespace mapping svcutil.exe /t:metadata TestSvcUtil\bin\debug\TestService.CustomerService.dll TestSvcUtil\bin\debug\TestService.StoreService.dll svcutil.exe /t:code *.wsdl *.xsd /o:TestClient\WebServiceProxy.cs The generated proxy looks like namespace mydomain.com.xsd.Model.Shared._2009._07._011 { public partial class Customer{} } namespace mydomain.com.xsd.Model.Customer._2009._07._011 { public partial class Address{} } namespace mydomain.com.xsd.Model.Store._2009._07._011 { public partial class Address{} } The client classes are out of any namespaces. Any change to xsd namespace would imply changing all using statements in my client code all build will break. 2. svcutil - with wildcard namespace mapping svcutil.exe /t:metadata TestSvcUtil\bin\debug\TestService.CustomerService.dll TestSvcUtil\bin\debug\TestService.StoreService.dll svcutil.exe /t:code *.wsdl *.xsd /n:*,MyDomain.ServiceProxy /o:TestClient\WebServicesProxy2.cs The generated proxy looks like namespace MyDomain.ServiceProxy { public partial class Customer{} public partial class Address{} public partial class Address1{} public partial class CustomerServiceClient{} public partial class StoreServiceClient{} } Notice that svcutil has automatically changed one of the Address class to Address1. I don't like this. All client classes are also inside the same namespace. What I want Something like this: svcutil.exe /t:code *.wsdl *.xsd /n:"http://mydomain.com/xsd/Model/Shared/2009/07/01, MyDomain.Model.Shared;http://mydomain.com/xsd/Model/Customer/2009/07/01, MyDomain.Model.Customer;http://mydomain.com/wsdl/CustomerService-v1.0, MyDomain.CustomerServiceProxy;http://mydomain.com/xsd/Model/Store/2009/07/01, MyDomain.Model.Store;http://mydomain.com/wsdl/StoreService-v1.0, MyDomain.StoreServiceProxy" /o:TestClient\WebServiceProxy3.cs This way I can logically group the clr namespace and any change to wsdl/xsd namespace is handled in the proxy generation only without affecting the rest of the client side code. Now this is not possible. The svcutil allows to map only one or all namespaces, not a list of mappings. I can do one mapping as shown below but not multiple svcutil.exe /t:code *.wsdl *.xsd /n:"http://mydomain.com/xsd/Model/Store/2009/07/01, MyDomain.Model.Address" /o:TestClient\WebServiceProxy4.cs But is there any solution. Svcutil is not magic, it is written in .Net and programatically generating the proxies. Has anyone written an alternate to svcutil or point me to directions so that I can write one.

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  • Git for beginners: The definitive practical guide

    - by Adam Davis
    Ok, after seeing this post by PJ Hyett, I have decided to skip to the end and go with git. So what I need is a beginners practical guide to git. "Beginner" being defined as someone who knows how to handle their compiler, understands to some level what a makefile is, and has touched source control without understanding it very well. "Practical" being defined as this person doesn't want to get into great detail regarding what git is doing in the background, and doesn't even care (or know) that it's distributed. Your answers might hint at the possibilities, but try to aim for the beginner that wants to keep a 'main' repository on a 'server' which is backed up and secure, and treat their local repository as merely a 'client' resource. Procedural note: PLEASE pick one and only one of the below topics and answer it clearly and concisely in any given answer. Don't try to jam a bunch of information into one answer. Don't just link to other resources - cut and paste with attribution if copyright allows, otherwise learn it and explain it in your own words (ie, don't make people leave this page to learn a task). Please comment on, or edit, an already existing answer unless your explanation is very different and you think the community is better served with a different explanation rather than altering the existing explanation. So: Installation/Setup How to install git How do you set up git? Try to cover linux, windows, mac, think 'client/server' mindset. Setup GIT Server with Msysgit on Windows How do you create a new project/repository? How do you configure it to ignore files (.obj, .user, etc) that are not really part of the codebase? Working with the code How do you get the latest code? How do you check out code? How do you commit changes? How do you see what's uncommitted, or the status of your current codebase? How do you destroy unwanted commits? How do you compare two revisions of a file, or your current file and a previous revision? How do you see the history of revisions to a file? How do you handle binary files (visio docs, for instance, or compiler environments)? How do you merge files changed at the "same time"? How do you undo (revert or reset) a commit? Tagging, branching, releases, baselines How do you 'mark' 'tag' or 'release' a particular set of revisions for a particular set of files so you can always pull that one later? How do you pull a particular 'release'? How do you branch? How do you merge branches? How do you resolve conflicts and complete the merge? How do you merge parts of one branch into another branch? What is rebasing? How do I track remote branches? How can I create a branch on a remote repository? Other Describe and link to a good gui, IDE plugin, etc that makes git a non-command line resource, but please list its limitations as well as its good. msysgit - Cross platform, included with git gitk - Cross platform history viewer, included with git gitnub - OS X gitx - OS X history viewer smartgit - Cross platform, commercial, beta tig - console GUI for Linux qgit - GUI for Windows, Linux Any other common tasks a beginner should know? Git Status tells you what you just did, what branch you have, and other useful information How do I work effectively with a subversion repository set as my source control source? Other git beginner's references git guide git book git magic gitcasts github guides git tutorial Progit - book by Scott Chacon Git - SVN Crash Course Delving into git Understanding git conceptually I will go through the entries from time to time and 'tidy' them up so they have a consistent look/feel and it's easy to scan the list - feel free to follow a simple "header - brief explanation - list of instructions - gotchas and extra info" template. I'll also link to the entries from the bullet list above so it's easy to find them later.

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  • Removing expired certificates from LDS (new ver of ADAM)

    - by jonthebrewer
    Hi all. This is my situation: We are in the process of replacing a certificate store currently hosted on Sun's iPlanet with Microsoft's Lightweight Directory Services (new version of ADAM with Server 2008). These certificates have been imported into LDS into an application partition (say o=myorg, C=AU). Under this structure I have around 40,000 OU's each one representing a customer under each customers OU are one or more user (iNetOrg) objects (around 60,000 in all). In each user are one or more certificates in the UserCertificate attribute. A combination of in-house written application code and proprietory PKI code reads and publishes these certficates to validate financial transactions. As the LDAP path of the certificates is stored within the customer certificates (and within the application code) and there is zero appetite for changing any of the code, I have had to pick up the iPlanet directory as a whole and dump it in LDS in the same structure. (I will not be using or hosting a Microsoft CA, just implementing an LDAP compliant directory to host these certificates) We have fully tested the application using the data in LDS and everything works fine - here is my dilema and question (finally, phew!) There was no process put in place for removing revoked or expired certificates, consequently the vast majority of the data is completely useless, the system has been running for about 8 years! I have done a quick analysis and I estimate that at least 80% of the data is no longer valid. As I am taking on responsibility for managing the directory I would like to start with a clean directory. Does anyone have any idea how I can cleanup these expired certificates. I am not a highly experienced scripter but have some background in VB. I have been researching the use of CAPICOM and have a feeling this may be able to be used but in exactly what way I am not sure?? I would prefer to write a script that I could specify an expiration date (say any certs that expired prior to 2010) then run against the LDS paritition. This way I can reuse the script periodically to cleanup the directory (as mentioned above - I have no way to adjust the applications that are writing the certs, this is with a third party). Another, less attractive, alternative is to massage the LDIF file (2.7 million lines!) to rip the certs out prior to the import Any help and advice MUCH appreciated. Cheers Jon

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  • JBoss EJB Bean not bound

    - by portoalet
    Hi, I have the following error Exception in thread "main" javax.naming.NameNotFoundException: CounterBean not bound trying to access an EJB JAR CounterBean.jar deployed on JBoss5 from a client application outside the Application Server. From the Jboss log, it looks like it does not have a global JNDI name? Is this ok? What have I done wrong? JBoss log: 13:50:39,669 INFO [JBossASKernel] Created KernelDeployment for: Counter.jar 13:50:39,672 INFO [JBossASKernel] installing bean: jboss.j2ee:jar=Counter.jar,name=CounterBean,service=EJB3 13:50:39,672 INFO [JBossASKernel] with dependencies: 13:50:39,672 INFO [JBossASKernel] and demands: 13:50:39,673 INFO [JBossASKernel] partition:partitionName=DefaultPartition; Required: Described 13:50:39,673 INFO [JBossASKernel] jboss.ejb:service=EJBTimerService; Required: Described 13:50:39,673 INFO [JBossASKernel] and supplies: 13:50:39,673 INFO [JBossASKernel] jndi:CounterBean 13:50:39,673 INFO [JBossASKernel] Added bean(jboss.j2ee:jar=Counter.jar,name=CounterBean,service=EJB3) to KernelDeployment of: Counte r.jar 13:50:39,712 INFO [SessionSpecContainer] Starting jboss.j2ee:jar=Counter.jar,name=CounterBean,service=EJB3 13:50:39,727 INFO [EJBContainer] STARTED EJB: com.don.CounterBean ejbName: CounterBean 13:50:39,732 INFO [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI: The client code is: public static void main(String[] args) throws NamingException, InterruptedException { InitialContext ctx = new InitialContext(); Counter s = (Counter)ctx.lookup("CounterBean/remote"); for(int i = 0; i < 100; i++ ) { s.printCount(i); Thread.sleep(1000); } } Error message: java -Djava.naming.provider.url=jnp://123.123.123.123:1099 -Djava.naming.factory.initial=org.jnp.interfaces.NamingContextFactory com.don.Client Exception in thread "main" javax.naming.NameNotFoundException: CounterBean not bound at org.jnp.server.NamingServer.getBinding(NamingServer.java:771) at org.jnp.server.NamingServer.getBinding(NamingServer.java:779) at org.jnp.server.NamingServer.getObject(NamingServer.java:785) at org.jnp.server.NamingServer.lookup(NamingServer.java:396) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:305) at sun.rmi.transport.Transport$1.run(Transport.java:159) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Transport.java:155) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255) at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:142) at org.jnp.server.NamingServer_Stub.lookup(Unknown Source) at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:726) at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:686) at javax.naming.InitialContext.lookup(InitialContext.java:392) at com.don.Client.main(Client.java:10)

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  • Resons why I'm using php rather then asp.net [closed]

    - by spirytus
    I have basic idea of how asp .Net works, but finds all framework hard to use if you are a newbie. I found compiling, web applications vs websites and all that stuff you should know to program in asp .net a bit tedious and so personally I go with php to create small, to medium applications for my clients. There are couple of reasons for it: php is easy scripting language, top to bottom and you done. You still can create objects, classes and if you have idea of MVC its fairly easy to create basic structure yourself so you can keep you presentation layer "relatively" clean. Although I find myself still mixing basic logic in my view's, I am trying to stick to booleans, and for each loops. ASP .net keeps it cleaner as far as I know and I agree that this is great. Heaps of free stuff for php and lots of help everywhere Although choice of IDE's for php is very limited, I still don't have to be stuck with VisualStudio. Lets be honest.. you can program in whatever you like but does anyone uses anything else other than VS? For basic applications I create, Visual Studio doesn't come even close to notepad :) / phpEdit (or similar) combination. It lacks of many features I constantly use, although armies of developers are using it and it must be for good reason. Personally not a big fan of VS though. Being on the market for that long should make editing much easier. I know .Net comes with awesome set of controls, validators etc. which is truly awesome. For me the problem starts if I want my validator to behave slightly different way and lets say fade in/out error messages. I know its possible to extend it behavior, plug into lifecycle and output different JS to the client and so on. I just never see it happen in places I work, and honestly, I don't even think most of .net developers I worked with during last couple of years would know how to do that. In php I have to grab some plugin for jQuery and use it for validation, which is fairly easy task once you had done it before. Again I'm sure its easy for .net gurus, but for newbie like me its almost impossible. I found that many asp .net programmers are very limited in what they are able to do and basically whack together .net applications using same lame set of controls, not even bothering in looking into how it works and what if? Now I don't want to anger anyone :) I know there is huge number of excellent .Net developers who know their stuff and are able to extend controls and do all that magic in no time. I found it a bit annoying though that many of them stick to what is provided without even trying to make it better. Nothing against .net here, just a thought really :) I remember when asp.net came out the idea was that front-end people will not be able to screw anything up and do their fron-end stuff without worrying what happens behind. Now its never that easy and I always tend to get server side people to fix this and that during development. Things like ID's assigned to controls can very easily make your application break and if someone is pure HTML guy using VS its easy to break something. Thats my thoughs on php and .net and reasons why for my work I go with php. I know that once learned asp .net is awesome technology and summing all up php doesn't even come close to it. For someone like me however, individually developing small basic applications for clients, php seems to work much better. Please let me know your thoughts on the above :)

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  • Reliable way of generating unique hardware ID

    - by mr.b
    Question: what's the best way to accomplish following. I have to come up with unique ID for each networked client, such that: it (ID) should persist once client software is installed on target computer, and should continue to persist if software is re-installed on same computer and same OS installment, it should not change if hardware configuration is modified in most ways (except changing the motherboard) When hard drive with client software installed is cloned to another computer with identical hardware configuration (or, as similar as possible), client software should be aware of that change. A little bit of explanation and some back-story: This question is basically age old question that also touches topic of software copy-protection, as some of mechanisms used in that area are mentioned here. I should be clear at this point that I'm not looking for a copy-protection scheme. Please, read on. :) I'm working on a client-server software that is supposed to work in local network. One of problems I have to solve is to identify each unique client in network (not so much of a problem), so that I can apply certain attributes to every specific client, retain and enforce those attributes during deployment lifetime of a specific client. While I was looking for a solution, I was aware of following: Windows activation system uses some kind of heavy fingerprinting mechanism, that is extremely sensitive to hardware modifications, Disk imaging software copies along all Volume IDs (tied to each partition when formatted), and custom, uniquely generated IDs during installation process, during first run, or in any other way, that is strictly software in its nature, and stored in registry or on hard drive, so it's very easy to confuse two Obvious choice for this kind of problem would be to find out BIOS identifiers (not 100% sure if this is unique through identical motherboard models, though), as that's the only thing I can rely on, that isn't duplicated, transferred by cloning, and that can't be changed (at least not by using some user-space program). Everything else fails as either being not reliable (MAC cloning, anyone?), or too demanding (in terms that it's too sensitive to configuration changes). Am I missing something obvious here? Sub-question that I'd like to ask is, am I doing it correctly, architecture-wise? Perhaps there is a better tool for task that I have to accomplish... Another approach I had in mind is something similar to handshake mechanism, where server maintains internal lookup table of connected client IDs (which can be even completely software-based and non-unique at any given moment), and tells client to come up with different ID during handshake, if duplicate ID is provided upon connection. That approach, unfortunately, doesn't play nicely with one of requirements to tie attributes to specific client during lifetime.

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  • Connecting to Active Directory Application Mode from Perl

    - by Khurram Aziz
    I am trying to connect to Active Directory Application Mode instance. The instance is conenctable from third party LDAP clients like Softerra LDAP Browser. But I am getting the following error when connecting from Perl Net::LDAP=HASH(0x876d8e4) sending: Net::LDAP=HASH(0x876d8e4) received: 30 84 00 00 00 A7 02 01 02 65 84 00 00 00 9E 0A 0........e...... 01 01 04 00 04 84 00 00 00 93 30 30 30 30 30 34 ..........000004 44 43 3A 20 4C 64 61 70 45 72 72 3A 20 44 53 49 DC: LdapErr: DSI 44 2D 30 43 30 39 30 36 32 42 2C 20 63 6F 6D 6D D-0C09062B, comm 65 6E 74 3A 20 49 6E 20 6F 72 64 65 72 20 74 6F ent: In order to 20 70 65 72 66 6F 72 6D 20 74 68 69 73 20 6F 70 perform this op 65 72 61 74 69 6F 6E 20 61 20 73 75 63 63 65 73 eration a succes 73 66 75 6C 20 62 69 6E 64 20 6D 75 73 74 20 62 sful bind must b 65 20 63 6F 6D 70 6C 65 74 65 64 20 6F 6E 20 74 e completed on t 68 65 20 63 6F 6E 6E 65 63 74 69 6F 6E 2E 2C 20 he connection., 64 61 74 61 20 30 2C 20 76 65 63 65 00 __ __ __ data 0, vece.` My directory structure is Partition: CN=Apps,DC=MyCo,DC=COM User exists as CN=myuser,CN=Apps,DC=MyCo,DC=COM I have couple of other entries of the custom class which I am interested to browse; those instances appear fine in ADSI Edit, Softerra LDAP Browser etc. I am new to Perl....My perl code is #!/usr/bin/perl use Net::LDAP; $ldap = Net::LDAP->new("127.0.0.1", debug => 2, user => "CN=myuser,CN=Apps,DC=MyCo,DC=COM", password => "secret" ) or die "$@"; $ldap->bind(version => 3) or die "$@"; print "Connected to ldap\n"; $mesg = $ldap->search( filter => "(objectClass=*)" ) or die ("Failed on search.$!"); my $max = $mesg->count; print "$max records found!\n"; for( my $index = 0 ; $index < $max ; $index++) { my $entry = $mesg->entry($index); my $dn = $entry->dn; @attrs = $entry->attributes; foreach my $var (@attrs) { $attr = $entry->get_value( $var, asref => 1 ); if ( defined($attr) ) { foreach my $value ( @$attr ) { print "$var: $value\n"; } } } } $ldap->unbind();

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  • Finding minimum cut-sets between bounded subgraphs

    - by Tore
    If a game map is partitioned into subgraphs, how to minimize edges between subgraphs? I have a problem, Im trying to make A* searches through a grid based game like pacman or sokoban, but i need to find "enclosures". What do i mean by enclosures? subgraphs with as few cut edges as possible given a maximum size and minimum size for number of vertices for each subgraph that act as a soft constraints. Alternatively you could say i am looking to find bridges between subgraphs, but its generally the same problem. Given a game that looks like this, what i want to do is find enclosures so that i can properly find entrances to them and thus get a good heuristic for reaching vertices inside these enclosures. So what i want is to find these colored regions on any given map. My Motivation The reason for me bothering to do this and not just staying content with the performance of a simple manhattan distance heuristic is that an enclosure heuristic can give more optimal results and i would not have to actually do the A* to get some proper distance calculations and also for later adding competitive blocking of opponents within these enclosures when playing sokoban type games. Also the enclosure heuristic can be used for a minimax approach to finding goal vertices more properly. A possible solution to the problem is the Kernighan-Lin algorithm: function Kernighan-Lin(G(V,E)): determine a balanced initial partition of the nodes into sets A and B do A1 := A; B1 := B compute D values for all a in A1 and b in B1 for (i := 1 to |V|/2) find a[i] from A1 and b[i] from B1, such that g[i] = D[a[i]] + D[b[i]] - 2*c[a][b] is maximal move a[i] to B1 and b[i] to A1 remove a[i] and b[i] from further consideration in this pass update D values for the elements of A1 = A1 / a[i] and B1 = B1 / b[i] end for find k which maximizes g_max, the sum of g[1],...,g[k] if (g_max > 0) then Exchange a[1],a[2],...,a[k] with b[1],b[2],...,b[k] until (g_max <= 0) return G(V,E) My problem with this algorithm is its runtime at O(n^2 * lg(n)), i am thinking of limiting the nodes in A1 and B1 to the border of each subgraph to reduce the amount of work done. I also dont understand the c[a][b] cost in the algorithm, if a and b do not have an edge between them is the cost assumed to be 0 or infinity, or should i create an edge based on some heuristic. Do you know what c[a][b] is supposed to be when there is no edge between a and b? Do you think my problem is suitable to use a multi level problem? Why or why not? Do you have a good idea for how to reduce the work done with the kernighan-lin algorithm for my problem?

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  • A little bit of Ajax goes a long way

    - by Holland
    ..except when you're having problems. My problem is this: I have a hierarchical list of categories stored in a database which I wish to output in a dropdown list. The hierarchy comes into place when the subcategories are to be displayed, which are dependent on a parent id (which equals out to the first seven or so main categories listed). My thoughts are relatively simple: when the user clicks the dynamically allocated list of main categories, they are clicking on an option tag. For each option tag, an id (i.e., the parent) is listed in the value attribute, as well as an argument which is sent to a Javascript function which then uses AJAX to get the data via PHP and sends it to my 'javascript.php' file. The file then does magic, and populates the subcategory list, which is dependent on the main category selected. I believe I have the idea down, it's just that I'm implementing the solution improperly, for some reason. Here's what I have so far: from javascript.php <script type="text/javascript" src=<?=JPATH_BASE.DS.'includes'.DS.'jquery.js';?>> var ajax = { ajax.sendAjaxData = function(method, url, dataTitle, ajaxData) { $.ajax({ type: 'post', url: "C:/wamp/www/patention/components/com_adsmanagar/views/edit/tmpl/javascript.php", data: { 'data' : ajaxData }, success: function(result){ // we have the response alert("Your request was successful." + result); }, error: function(e){ alert('Error: ' + e); } }); } ajax.printSubCategoriesOnClick = function(parent) { alert("hello world!"); ajax.sendAjaxData('post', 'javascript.php', 'data' parent); <?php $categories = $this->formData->getCategories($_POST['data']); ?> ajax.printSubCategories(<?=$categories;?>); } ajax.printSubCategories = function(categories) { var select = document.getElementById("subcategories"); for (var i = 0; i < categories.length; i++) { var opt = document.createElement("option"); opt.text = categories['name']; opt.value = categories['id']; } } } </script> the function used to populate the form data function populateCategories($parent, FormData $formData) { $categories = $formData->getCategories($parent); echo "<pre>"; print_r($categories); echo "</pre>"; foreach($categories as $section => $row){ ?> <option value=<?=$row['id'];?> onclick="ajax.printSubCategoriesOnClick(<?=$row['id']?>)"> <? echo $row['name']; ?> </option> <?php } } The problem is that when I try to do a print_r on my $_POST variable, nothing shows up. I also receive an "undefined index" error (which refers to the key I set for the data type). I'm thinking that for some reason, the data is being sent to my form.php file, or my default.php file which includes both the form.php and javascript.php files via a function. Is there something specific that I'm missing here? Just looking up basic AJAX syntax (via jQuery) hasn't helped out, unfortunately.

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  • ASP.net roles and Projects

    - by Zyphrax
    EDIT - Rewrote my original question to give a bit more information Background info At my work I'm working on a ASP.Net web application for our customers. In our implementation we use technologies like Forms authentication with MembershipProviders and RoleProviders. All went well until I ran into some difficulties with configuring the roles, because the roles aren't system-wide, but related to the customer accounts and projects. I can't name our exact setup/formula, because I think our company wouldn't approve that... What's a customer / project? Our company provides management information for our customers on a yearly (or other interval) basis. In our systems a customer/contract consists of: one Account: information about the Company per Account, one or more Products: the bundle of management information we'll provide per Product, one or more Measurements: a period of time, in which we gather and report the data Extranet site setup Eventually we want all customers to be able to access their management information with our online system. The extranet consists of two sites: Company site: provides an overview of Account information and the Products Measurement site: after selecting a Measurement, detailed information on that period of time The measurement site is the most interesting part of the extranet. We will create submodules for new overviews, reports, managing and maintaining resources that are important for the research. Our Visual Studio solution consists of a number of projects. One web application named Portal for the basis. The sites and modules are virtual directories within that application (makes it easier to share MasterPages among things). What kind of roles? The following users (read: roles) will be using the system: Admins: development users :) (not customer related, full access) Employees: employees of our company (not customer related, full access) Customer SuperUser: top level managers (full access to their account/measurement) Customer ContactPerson: primary contact (full access to their measurement(s)) Customer Manager: a department manager (limited access, specific data of a measurement) What about ASP.Net users? The system will have many ASP.Net users, let's focus on the customer users: Users are not shared between Accounts SuperUser X automatically has access to all (and new) measurements User Y could be Primary contact for Measurement 1, but have no role for Measurement 2 User Y could be Primary contact for Measurement 1, but have a Manager role for Measurement 2 The department managers are many individual users (per Measurement), if Manager Z had a login for Measurement 1, we would like to use that login again if he participates in Measurement 2. URL structure These are typical urls in our application: http://host/login - the login screen http://host/project - the account/product overview screen (measurement selection) http://host/project/1000 - measurement (id:1000) details http://host/project/1000/planning - planning overview (for primary contact/superuser) http://host/project/1000/reports - report downloads (manager department X can only access report X) We will also create a document url, where you can request a specific document by it's GUID. The system will have to check if the user has rights to the document. The document is related to a Measurement, the User or specific roles have specific rights to the document. What's the problem? (finally ;)) Roles aren't enough to determine what a user is allowed to see/access/download a specific item. It's not enough to say that a certain navigation item is accessible to Managers. When the user requests Measurement 1000, we have to check that the user not only has a Manager role, but a Manager role for Measurement 1000. Summarized: How can we limit users to their accounts/measurements? (remember superusers see all measurements, some managers only specific measurements) How can we apply roles at a product/measurement level? (user X could be primarycontact for measurement 1, but just a manager for measurement 2) How can we limit manager access to the reports screen and only to their department's reports? All with the magic of asp.net classes, perhaps with a custom roleprovider implementation. Similar Stackoverflow question/problem http://stackoverflow.com/questions/1367483/asp-net-how-to-manage-users-with-different-types-of-roles

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  • Best way to handle multiple tables to replace one big table in Rails? (e.g. 'Books1', 'Books2', etc.

    - by mikep
    Hello, I've decided to use multiple tables for an entity (e.g. Books1, Books2, Books3, etc.), instead of just one main table which could end up having a lot of rows (e.g. just Books). I'm doing this to try and to avoid a potential future performance drop that could come with having too many rows in one table. With that, I'm looking for a good way to handle this in Rails, mainly by trying to avoid loading a bunch of unused associations. (I know that I could use a partition for this, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. I'm going to split the adds across the tables. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end class Books3 < ActiveRecord::Base belongs_to :user end I'm assuming that the main performance hit would come in terms of memory and possibly some method call overhead for each User object, since it has to load all of those associations, which in turn creates all of those nice, dynamic model accessor methods like User.find_by_. But for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. For example, with a user.id of 2, I'd only need books3.find_by_author('Author'), but the way I'm thinking of setting this up, I'd still have access to Books1..n. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. So, a few questions: 1) Is there's some sort of special Ruby/Rails methodology that could be applied to this 'multiple tables to represent one entity' scheme? Are there any 'best practices' for this? 2) Is it really bad to have so many unused has_many associations for each object? Is there a better way to do this? 3) Does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class? For example, so I can call books.find_by_author('Author') instead of books3.find_by_author('Author'). Thank you!

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  • How does one track down an error using the YII Framework?

    - by ian
    I am learning the Yii Framework and I got this error wich does not really point to the specific pages I am working on or as far as i can tell show me where I should start looking for my problem. How do I make sense of this? As far as I can see all my 'type_id' references are typed in correctly. CException Description Property "Project.type_id" is not defined. Source File /Users/user/Dropbox/localhost/yii/framework/db/ar/CActiveRecord.php(107) 00095: */ 00096: public function __get($name) 00097: { 00098: if(isset($this->_attributes[$name])) 00099: return $this->_attributes[$name]; 00100: else if(isset($this->getMetaData()->columns[$name])) 00101: return null; 00102: else if(isset($this->_related[$name])) 00103: return $this->_related[$name]; 00104: else if(isset($this->getMetaData()->relations[$name])) 00105: return $this->getRelated($name); 00106: else 00107: return parent::__get($name); 00108: } 00109: 00110: /** 00111: * PHP setter magic method. 00112: * This method is overridden so that AR attributes can be accessed like properties. 00113: * @param string property name 00114: * @param mixed property value 00115: */ 00116: public function __set($name,$value) 00117: { 00118: if($this->setAttribute($name,$value)===false) 00119: { Stack Trace #0 /Users/user/Dropbox/localhost/yii/framework/db/ar/CActiveRecord.php(107): CComponent->__get('type_id') #1 /Users/user/Dropbox/localhost/trackstar/protected/views/project/_view.php(15): CActiveRecord->__get('type_id') #2 /Users/user/Dropbox/localhost/yii/framework/web/CBaseController.php(119): require('/Users/user/Dro...') #3 /Users/user/Dropbox/localhost/yii/framework/web/CBaseController.php(88): CBaseController->renderInternal('/Users/user/Dro...', Array, true) #4 /Users/user/Dropbox/localhost/yii/framework/web/CController.php(748): CBaseController->renderFile('/Users/user/Dro...', Array, true) #5 /Users/user/Dropbox/localhost/yii/framework/zii/widgets/CListView.php(215): CController->renderPartial('_view', Array) #6 /Users/user/Dropbox/localhost/yii/framework/zii/widgets/CBaseListView.php(152): CListView->renderItems() #7 [internal function]: CBaseListView->renderSection(Array) #8 /Users/user/Dropbox/localhost/yii/framework/zii/widgets/CBaseListView.php(135): preg_replace_callback('/{(\w+)}/', Array, '{summary}?{sort...') #9 /Users/user/Dropbox/localhost/yii/framework/zii/widgets/CBaseListView.php(121): CBaseListView->renderContent() #10 /Users/user/Dropbox/localhost/yii/framework/web/CBaseController.php(174): CBaseListView->run() #11 /Users/user/Dropbox/localhost/trackstar/protected/views/project/index.php(17): CBaseController->widget('zii.widgets.CLi...', Array) #12 /Users/user/Dropbox/localhost/yii/framework/web/CBaseController.php(119): require('/Users/user/Dro...') #13 /Users/user/Dropbox/localhost/yii/framework/web/CBaseController.php(88): CBaseController->renderInternal('/Users/user/Dro...', Array, true) #14 /Users/user/Dropbox/localhost/yii/framework/web/CController.php(748): CBaseController->renderFile('/Users/user/Dro...', Array, true) #15 /Users/user/Dropbox/localhost/yii/framework/web/CController.php(687): CController->renderPartial('index', Array, true) #16 /Users/user/Dropbox/localhost/trackstar/protected/controllers/ProjectController.php(148): CController->render('index', Array) #17 /Users/user/Dropbox/localhost/yii/framework/web/actions/CInlineAction.php(32): ProjectController->actionIndex() #18 /Users/user/Dropbox/localhost/yii/framework/web/CController.php(300): CInlineAction->run() #19 /Users/user/Dropbox/localhost/yii/framework/web/filters/CFilterChain.php(129): CController->runAction(Object(CInlineAction)) #20 /Users/user/Dropbox/localhost/yii/framework/web/filters/CFilter.php(41): CFilterChain->run() #21 /Users/user/Dropbox/localhost/yii/framework/web/CController.php(999): CFilter->filter(Object(CFilterChain)) #22 /Users/user/Dropbox/localhost/yii/framework/web/filters/CInlineFilter.php(59): CController->filterAccessControl(Object(CFilterChain)) #23 /Users/user/Dropbox/localhost/yii/framework/web/filters/CFilterChain.php(126): CInlineFilter->filter(Object(CFilterChain)) #24 /Users/user/Dropbox/localhost/yii/framework/web/CController.php(283): CFilterChain->run() #25 /Users/user/Dropbox/localhost/yii/framework/web/CController.php(257): CController->runActionWithFilters(Object(CInlineAction), Array) #26 /Users/user/Dropbox/localhost/yii/framework/web/CWebApplication.php(320): CController->run('') #27 /Users/user/Dropbox/localhost/yii/framework/web/CWebApplication.php(120): CWebApplication->runController('project') #28 /Users/user/Dropbox/localhost/yii/framework/base/CApplication.php(135): CWebApplication->processRequest() #29 /Users/user/Dropbox/localhost/trackstar/index.php(12): CApplication->run() #30 {main} 2011-10-17 18:17:18 Apache/2.2.17 (Unix) mod_ssl/2.2.17 OpenSSL/0.9.8r DAV/2 PHP/5.3.6 Yii Framework/1.1.2

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  • NSMutableString leaks on append or replaceOccurrencesOfString

    - by John
    Hello Folks, I know similar questions have been asked time and time again but I ask that you please bear with me as I cannot seem to find an answer that helps. My application has leaks that are driving me out of my mind. Actually, they are not reported as leaks using Leaks, but my net bytes in ObjectAlloc goes up and up and up and never stops, eventually leading to a crash if it goes on long enough (not very long). The problem occurs with NSMutableStrings. I think there is either something fundamental I don't understand about them, or I am facing another problem that I am having difficulty tracking down but keeps hiding behind the NSMutableStrings. Specifically, I am noticing that whenever I append to or perform a replace on a NSMutableString, ObjectAlloc reports what appear to be mismatches in malloc/frees behind the scene when resizing the NSMutableString. I'm sorry to say this is the second time I'm facing this problem - the first time I messed around for hours and hours and finally the problem went away (magic!) but I don't really know why. When I look at the code below (and believe me, I've stared at it for hours) I cannot see the problem. I look at the code and think to myself that I should be fine because I'm releasing the only object for which I am responsible (aString) and that NSMutableString should be taking care of cleaning up after any resizing it does. In the second example, just so you know in case it helps, the string being passed in comes from an ASIHTTPRequest object (it's the responseString) and I don't do anything at all with it. It's being called simply like so ([self DoStuff2:[request responseString]]) and I don't free the request myself either (I'm using a ASINetworkQueue and I assume that the requests are destroyed for me (I tried and caused errors because the request was already being release somewhere else). Also, I know it shouldn't do anything, but I even tried wrapping the code in autorelease pools, which of course did nothing. I should mention that this code is being run inside of an NSOperation. I thought that perhaps I am experiencing problems because NSOperations should create an autorelease pool for themselves, but I've tried that to no avail. Not related to NSMutableString, but I find I also have similar problems using the NSString componentsSeparatedByString method. Sometimes the memory used by the array that gets the separated components is never released. Hmmm...strings in general seem to be somewhat problematic for me it seems. I would appreciate ANY help anyone can provide. If you require more info, I'll be glad to add it. I do promise you that I've struggled with this (and other problems) for weeks and every problem I encounter I research hard and long until I find a solution - this is not an idle request, but a true cry for help! I've written so much code and now I'm trying to seal some small leaks etc and I notice this problem. Honestly, I cannot believe how memory management in Objective C can stump me so at times...I've read Apple's memory mgmt docs many times and I thought I thoroughly understood it and I try to be diligent about releasing objects I own, but sometimes I find myself wondering if I truly understand...I would like to put this to bed once and make sure I understand all this fully - to have this sort of question/problem after writing thousands of lines of code is more than a little scary/embarrassing/annoying. So again, if anybody has any insight, I'd be grateful. Thanks for your time and efforts. -(void)DoStuff { NSString *aString [ [[NSString alloc] initWithFormat:@"text %@ more text", self.strVariable]; [self.someMutableStringVar replaceOccurrencesOfString:@"replace" withString:aString options:NSCaseInsensitiveSearch range:NSMakeRange(0, [self.someMutableStringVar length])]; [aString release]; } -(void)DoStuff2:(NSString *)aString { [self.someMutableStringVar appendString:aString]; }

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  • Is the design notion of layers contrived?

    - by Bruce
    Hi all I'm reading through Eric Evans' awesome work, Domain-Driven Design. However, I can't help feeling that the 'layers' model is contrived. To expand on that statement, it seems as if it tries to shoe-horn various concepts into a specific, neat model, that of layers talking to each other. It seems to me that the layers model is too simplified to actually capture the way that (good) software works. To expand further: Evans says: "Partition a complex program into layers. Develop a design within each layer that is cohesive and that depends only on the layers below. Follow standard architectural patterns to provide loose coupling to the layers above." Maybe I'm misunderstanding what 'depends' means, but as far as I can see, it can either mean a) Class X (in the UI for example) has a reference to a concrete class Y (in the main application) or b) Class X has a reference to a class Y-ish object providing class Y-ish services (ie a reference held as an interface). If it means (a), then this is clearly a bad thing, since it defeats re-using the UI as a front-end to some other application that provides Y-ish functionality. But if it means (b), then how is the UI any more dependent on the application, than the application is dependent on the UI? Both are decoupled from each other as much as they can be while still talking to each other. Evans' layer model of dependencies going one way seems too neat. First, isn't it more accurate to say that each area of the design provides a module that is pretty much an island to itself, and that ideally all communication is through interfaces, in a contract-driven/responsibility-driven paradigm? (ie, the 'dependency only on lower layers' is contrived). Likewise with the domain layer talking to the database - the domain layer is as decoupled (through DAO etc) from the database as the database is from the domain layer. Neither is dependent on the other, both can be swapped out. Second, the idea of a conceptual straight line (as in from one layer to the next) is artificial - isn't there more a network of intercommunicating but separate modules, including external services, utility services and so on, branching off at different angles? Thanks all - hoping that your responses can clarify my understanding on this..

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  • Problem with URL encoded parameters in URL view helper

    - by Richard Knop
    So my problem is kinda weird, it only occurs when I test the application offline (on my PC with WampServer), the same code works 100% correctly online. Here is how I use the helper (just example): <a href="<?php echo $this->url(array('module' => 'admin', 'controller' => 'index', 'action' => 'approve-photo', 'id' => $this->escape($a->id), 'ret' => urlencode('admin/index/photos')), null, true); ?>" class="blue">approve</a> Online, this link works great, it goes to the action which looks similar to this: public function approvePhotoAction() { $request = $this->getRequest(); $photos = $this->_getTable('Photos'); $dbTrans = false; try { $db = $this->_getDb(); $dbTrans = $db->beginTransaction(); $photos->edit($request->getParam('id'), array('status' => 'approved')); $db->commit(); } catch (Exception $e) { if (true === $dbTrans) { $db->rollBack(); } } $this->_redirect(urldecode($request->getParam('ret'))); } So online, it approves the photo and redirects back to the URL that is encoded as "ret" param in the URL ("admin/index/photos"). But offline with WampServer I click on the link and get 404 error like this: Not Found The requested URL /public/admin/index/approve-photo/id/1/ret/admin/index/photos was not found on this server. What the hell? I'm using the latest version of WampServer (WampServer 2.0i [11/07/09]). Everything else works. Here is my .htaccess file, just in case: RewriteEngine On RewriteCond %{REQUEST_FILENAME} -s [OR] RewriteCond %{REQUEST_FILENAME} -l [OR] RewriteCond %{REQUEST_FILENAME} -d RewriteRule ^.*$ - [NC,L] RewriteRule ^.*$ /index.php [NC,L] # Turn off magic quotes #php_flag magic_quotes_gpc off I'm using virtual hosts to test ZF projects on my local PC. Here is how I add virtual hosts. httpd.conf: NameVirtualHost *:80 <VirtualHost *:80> ServerName myproject DocumentRoot "C:\wamp\www\myproject" </VirtualHost> the hosts file: 127.0.0.1 myproject Any help would be appreciated because this makes testing and debugging projects on my localhost a nightmare and almost impossible task. I have to upload everything online to check if it works :( UPDATE: Source code of the _redirect helper (built in ZF helper): /** * Set redirect in response object * * @return void */ protected function _redirect($url) { if ($this->getUseAbsoluteUri() && !preg_match('#^(https?|ftp)://#', $url)) { $host = (isset($_SERVER['HTTP_HOST'])?$_SERVER['HTTP_HOST']:''); $proto = (isset($_SERVER['HTTPS'])&&$_SERVER['HTTPS']!=="off") ? 'https' : 'http'; $port = (isset($_SERVER['SERVER_PORT'])?$_SERVER['SERVER_PORT']:80); $uri = $proto . '://' . $host; if ((('http' == $proto) && (80 != $port)) || (('https' == $proto) && (443 != $port))) { $uri .= ':' . $port; } $url = $uri . '/' . ltrim($url, '/'); } $this->_redirectUrl = $url; $this->getResponse()->setRedirect($url, $this->getCode()); } UPDATE 2: Output of the helper offline: /admin/index/approve-photo/id/1/ret/admin%252Findex%252Fphotos And online (the same): /admin/index/approve-photo/id/1/ret/admin%252Findex%252Fphotos UPDATE 3: OK. The problem was actually with the virtual host configuration. The document root was set to C:\wamp\www\myproject instead of C:\wamp\www\myproject\public. And I was using this htaccess to redirect to the public folder: RewriteEngine On php_value upload_max_filesize 15M php_value post_max_size 15M php_value max_execution_time 200 php_value max_input_time 200 # Exclude some directories from URI rewriting #RewriteRule ^(dir1|dir2|dir3) - [L] RewriteRule ^\.htaccess$ - [F] RewriteCond %{REQUEST_URI} ="" RewriteRule ^.*$ /public/index.php [NC,L] RewriteCond %{REQUEST_URI} !^/public/.*$ RewriteRule ^(.*)$ /public/$1 RewriteCond %{REQUEST_FILENAME} -f RewriteRule ^.*$ - [NC,L] RewriteRule ^public/.*$ /public/index.php [NC,L] Damn it I don't know why I forgot about this, I thought the virtual host was configured correctly to the public folder, I was 100% sure about that, I also double checked it and saw no problem (wtf? am I blind?).

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  • Python/numpy tricky slicing problem

    - by daver
    Hi stack overflow, I have a problem with some numpy stuff. I need a numpy array to behave in an unusual manner by returning a slice as a view of the data I have sliced, not a copy. So heres an example of what I want to do: Say we have a simple array like this: a = array([1, 0, 0, 0]) I would like to update consecutive entries in the array (moving left to right) with the previous entry from the array, using syntax like this: a[1:] = a[0:3] This would get the following result: a = array([1, 1, 1, 1]) Or something like this: a[1:] = 2*a[:3] # a = [1,2,4,8] To illustrate further I want the following kind of behaviour: for i in range(len(a)): if i == 0 or i+1 == len(a): continue a[i+1] = a[i] Except I want the speed of numpy. The default behavior of numpy is to take a copy of the slice, so what I actually get is this: a = array([1, 1, 0, 0]) I already have this array as a subclass of the ndarray, so I can make further changes to it if need be, I just need the slice on the right hand side to be continually updated as it updates the slice on the left hand side. Am I dreaming or is this magic possible? Update: This is all because I am trying to use Gauss-Seidel iteration to solve a linear algebra problem, more or less. It is a special case involving harmonic functions, I was trying to avoid going into this because its really not necessary and likely to confuse things further, but here goes. The algorithm is this: while not converged: for i in range(len(u[:,0])): for j in range(len(u[0,:])): # skip over boundary entries, i,j == 0 or len(u) u[i,j] = 0.25*(u[i-1,j] + u[i+1,j] + u[i, j-1] + u[i,j+1]) Right? But you can do this two ways, Jacobi involves updating each element with its neighbours without considering updates you have already made until the while loop cycles, to do it in loops you would copy the array then update one array from the copied array. However Gauss-Seidel uses information you have already updated for each of the i-1 and j-1 entries, thus no need for a copy, the loop should essentially 'know' since the array has been re-evaluated after each single element update. That is to say, every time we call up an entry like u[i-1,j] or u[i,j-1] the information calculated in the previous loop will be there. I want to replace this slow and ugly nested loop situation with one nice clean line of code using numpy slicing: u[1:-1,1:-1] = 0.25(u[:-2,1:-1] + u[2:,1:-1] + u[1:-1,:-2] + u[1:-1,2:]) But the result is Jacobi iteration because when you take a slice: u[:,-2,1:-1] you copy the data, thus the slice is not aware of any updates made. Now numpy still loops right? Its not parallel its just a faster way to loop that looks like a parallel operation in python. I want to exploit this behaviour by sort of hacking numpy to return a pointer instead of a copy when I take a slice. Right? Then every time numpy loops, that slice will 'update' or really just replicate whatever happened in the update. To do this I need slices on both sides of the array to be pointers. Anyway if there is some really really clever person out there that awesome, but I've pretty much resigned myself to believing the only answer is to loop in C.

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