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Articles indexed in February 2011

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• How to make a server check it's own availability on the web?

  - by Javawag

  Hi all, Just a quick question – my server is running at my house serving www pages at www.javawag.com. The problem is that my home internet connection keeps dropping randomly - for about 10 mins at a time. This is only an intermittent problem and will go away soon I hope. However, my server doesn't recover properly - when the connection comes back, I can still access it at 192.168.0.8 (locally) without any issue, but at www.javawag.com there's no reply! (Just an aside - my home internet connection is dynamic ISP, the domain www.javawag.com points to javawag.dyndns.org which in turn points to my IP, updated every minute by ddclient on the server) Is there some way for the server to check if it's accessible from the outside world periodically, and if not restart Apache/reboot? Oh, and if I reboot the problem fixes itself also! Javawag

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• A website hosted on the 1.0.0.0/8 subnet, somewhere on the Internet?

  - by Dave Markle

  Background I'm attempting to demonstrate, using a real-world example, of why someone would not want to configure their internal network on the 1.0.0.0/8 subnet. Obviously it's because this is not designated as private address space. As of 2010, ARIN has apparently allocated 1.0.0.0/8 to APNIC (the Asia-Pacific NIC), who seems to have begun assigning addresses in that subnet, though not in 1.1.0.0/16, 1.0.0.0/16, and others (because these addresses are so polluted by bad network configurations all around the Internet). My Question My question is this: I'd like to find a website that responds on this subnet somewhere and use it as a counter-example, demonstrating to a non-technical user its inaccessibility from an internal network configured on 1.0.0.0/8. Other than writing a program to sniff all ~16 million hosts, looking for a response on port 80, does anyone know of a directory I can use, or even better yet, does anyone know of a site that's configured on this subnet? WHOIS seems to be too general of a search for me at this point...

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• How can I make IPv6 on OpenVPN work using a tap device?

  - by Lekensteyn

  I've managed to setup OpenVPN for full IPv4 connectivity using tap0. Now I want to do the same for IPv6. Addresses and network setup (note that my real prefix is replaced by 2001:db8): 2001:db8::100:0:0/96 my assigned IPv6 range 2001:db8::100:abc:0/112 OpenVPN IPv6 range 2001:db8::100:abc:1 tap0 server side (set as gateway on client) 2001:db8::100:abc:2 tap0 client side 2001:db8::1:2:3:4 gateway for server Home laptop (tap0: 2001:db8::100:abc:2/112 gateway 2001:db8::100:abc:1/112) | | | (running Kubuntu 10.10; OpenVPN 2.1.0-3ubuntu1) | wifi | | router | | OpenVPN INTERNET | eth0 | /tap0 VPS (eth0:2001:db8::1:2:3:4/64 gateway 2001:db8::1) (tap0: 2001:db8::100:abc:1/112) (running Debian 6; OpenVPN 2.1.3-2) The server has both native IPv4 and IPv6 connectivity, the client has only IPv4. I can ping6 to and from my server over OpenVPN, but not to other machines (for example, ipv6.google.com). Using tcpdump on both the server and client, I can see that packets are actually transferred over tap0 to eth0. The router (2001:db8::1) send a neighbor solicitation for the client (2001:db8::100:abc:2) to eth0 after it receives the ICMP6 echo-request. The server does not respond to that solicitation, which causes the ICMP6 echo-request not be routed to the destination. How can I make this IPv6 connection work?

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• knife server create- finding lists of flavors

  - by JohnMetta

  I'm new to Chef and I think I'm missing something in reading the docs. I want to create servers using knife server create (options) but can't seem to find fully complete documentation on the options. Specifically, how do I find a mapping of server flavors to whatever knife is looking for? Given the official wiki entry for "Launch Cloud Instances with Knife," the following is an example server creation on Rackspace: knife rackspace server create 'role[webserver]' --server-name server01 --image 49 --flavor 2 Likewise, on the Knife Man Page, there are commands for EC2 server images (using --d --distro DISTRO) and for Slicehost servers (using -f --flavor FLAVOR) However, what none of the documentation I've found describes is how to translate what I want to build on Rackspace ("I want Ubuntu 10.04 LTS") to what the integer entry that knife is seeking. It strikes me that, given the lack of a description in the documentation for how to find the flavor, this should be obvious. Thus, I think I'm missing something.

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• Windows 2008 R2 Servers Sending Arp Requests for IPs outside Subnet

  - by Kyle Brandt

  By running a packet capture on my my routers I see some of my servers sending ARP requests for IPs that exist outside of its network. For example if my network is: Network: 8.8.8.0/24 Gateway: 8.8.8.1 (MAC: 00:21:9b:aa:aa:aa) Example Server: 8.8.8.20 (MAC: 00:21:9b:bb:bb:bb) By running a capture on the interface that has 8.8.8.1 I see requests like: Sender Mac: 00:21:9b:bb:bb:bb Sender IP: 8.8.8.20 Target MAC: 00:21:9b:aa:aa:aa Target IP: 69.63.181.58 Anyone seen this behavior before? My understanding of ARP is that requests should only go out for IPs within the subnet... Am I confused in my understanding of ARP? If I am not confused, anyone seen this behavior? Also, these seem to happen in bursts and it doesn't happen when I do something like ping an IP outside of the network. Update: In response to Ian's questions. I am not running anything like Hyper-V. I have multiple interfaces but only one is active (Using BACS failover teaming). The subnet mask is 255.255.255.0 (Even if it were something different it wouldn't explain an IP like 69.63.181.58). When I run MS Network Monitor or wireshark I do not see these ARP requests. What happens is that on the router capturing I see a burst of about 10 requests for IPs outside of the network from the host machine. On the machine itself using wireshark or NetMon I see a flood of ARP responses for all the machines on the network. However, I don't see any requests in the capture asking for those responses. So it seems like maybe it is maybe refreshing the arp cache but including IPs that outside of the network. Also when it does this NetMon doesn't show the ARP requests?

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• Servers - Buying New vs Buying Second-hand

  - by Django Reinhardt

  We're currently in the process of adding additional servers to our website. We have a pretty simple topology planned: A Firewall/Router Server infront of a Web Application Server and Database Server. Here's a simple (and technically incorrect) diagram that I used in a previous question to illustrate what I mean: We're now wondering about the specs of our two new machines (the Web App and Firewall servers) and whether we can get away with buying a couple of old servers. (Note: Both machines will be running Windows Server 2008 R2.) We're not too concerned about our Firewall/Router server as we're pretty sure it won't be taxed too heavily, but we are interested in our Web App server. I realise that answering this type of question is really difficult without a ton of specifics on users, bandwidth, concurrent sessions, etc, etc., so I just want to focus on the general wisdom on buying old versus new. I had originally specced a new Dell PowerEdge R300 (1U Rack) for our company. In short, because we're going to be caching as much data as possible, I focussed on Processor Speed and Memory: Quad-Core Intel Xeon X3323 2.5Ghz (2x3M Cache) 1333Mhz FSB 16GB DDR2 667Mhz But when I was looking for a cheap second-hand machine for our Firewall/Router, I came across several machines that made our engineer ask a very reasonable question: If we stuck a boat load of RAM in this thing, wouldn't it do for the Web App Server and save us a ton of money in the process? For example, what about a second-hand machine with the following specs: 2x Dual-Core AMD Opteron 2218 2.6Ghz (2MB Cache) 1000Mhz HT 16GB DDR2 667Mhz Would it really be comparable with the more expensive (new) server above? Our engineer postulated that the reason companies upgrade their servers to newer processors is often because they want to reduce their power costs, and that a 2.6Ghz processor was still a 2.6Ghz processor, no matter when it was made. Benchmarks on various sites don't really support this theory, but I was wondering what server admin thought. Thanks for any advice.

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• Linux stretch cluster: MD replication, DRBD or Veritas?

  - by PieterB

  For the moment there's a lot of choices for setting up a Linux cluster. For cluster manager: you can use Red Hat Cluster manager, Pacemaker or Veritas Cluster Server. The first one has the most momentum, the second one comes by default with RH subscriptions and the last one is very expensive and has a very good reputation ;-) For storage: - You can replicate LUN's using software raid / md device - You can use the network using DRBD replication, which offers a bit more flexibility - You can use Veritas Storage Foundation technology to talk to your SANs replication technology. Anyone has any recommandations or experience with these technologies?

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• Update Grub on Squeeze - Kernel downgrade due VMware Server

  - by vodoo_boot

  Hi! I happen to run into various problems regarding grub and kernels. I don't really care about the kernel internas. All I want is VMware server in that dedicated root-server. 1.) What is a bzImage vs. vmlinuz? kaze:~# ls /boot/ System.map-2.6.32-5-amd64 bzImage-2.6.33.2 config-2.6.33.2 initrd.img-2.6.32-5-amd64 System.map-2.6.33.2 bzImage-2.6.35.6 config-2.6.35.6 vmlinuz-2.6.32-5-amd64 System.map-2.6.35.6 config-2.6.32-5-amd64 grub I updated my menu.lst (grub2): timeout 5 default 0 fallback 1 title 2.6.32.5 kernel (hd0,1)/boot/vmlinuz-2.6.32-5-amd64 root=/dev/sda2 panic=60 noapic acpi=off title 2.6.35.6 kernel (hd0,1)/boot//bzImage-2.6.35.6 root=/dev/sda2 panic=60 noapic acpi=off title 2.6.32.3 kernel (hd0,1)/boot//bzImage-2.6.33.2 root=/dev/sda2 panic=60 noapic acpi=off That doesn't do well... I think the vmlinuz file is missing initrd or so. Dunno. In fact I don't give too much about kernel boot voodoo as long as it works. update-grub(2) does not work. Does anybody know what magical trick there is to get the 2.6.32-5 booting? 2.) I thought t follow the Deban wiki.. I cannot get header-files for the installed 35.6 or 33.2 kernel in the repositories. I cannot build foreign headers because they will not match the running kernel. So how does one deal with that situtation? I'd prefer not to have to downgrade the kernel. Thanks for any answers!

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• Sending e-mail on behalf of our customer(s), with Postfix

  - by NathanE

  We send e-mail on behalf of our customers, via our own SMTP services. It's always been a problem for us because usually our "spoofing" of their source address results in the mails being caught in spam traps. This hasn't been a problem in the past due to the small volume and low importance of these mails that we sent. However this requirement has recently changed and we need to fix this issue. We realise that fundamentally our application is sending e-mail incorrectly, as per this post: Send email on behalf of clients However, we would like to resolve the problem at the SMTP server level. We have deployed a server running Postfix. Is it possible to have Postfix automatically adjust the mail headers so that we get this "Sent on behalf of" behaviour? I figure it should just be a case of Postfix noticing that the FROM address is the spoofed (i.e. a domain that is not mentioned in its config anywhere) and therefore inject/replace the appropriate headers to get the desired effect. Thanks.

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• Oracle 11g Data Guard over a WAN

  - by Dave LeJeune

  Hi - We are in process of looking at using Oracle's Data Guard to replicate our 11g instance from a colo facility in Washington DC to Chicago. To give some basics we have approximately 25TB of storage and a healthy transaction rate in the 1-2K/sec range. Also, because we are processing data in real-time we have a 24x7x365 requirement for processing data. We don't have any respites as far as volume except for system upgrades (once every few months) where we take the system offline but then course experience a spike in transactions when we bring the system back on-line. Ideally we would want the second instance in the DG configuration semi-online in a read-only fashion for reports/etc. We evaluated DG in 10g and were not overly impressed and research seemed to show that earlier versions had issues with replication over a WAN but I have heard good things about modifications the product has gone through w/ 11g. Can anyone confirm an instance of this size and transaction rate being replicated over a WAN and if so what is the general latency? An information or experiences with a DG implementation that is of this size and scope would really be helpful (or larger - I also realize we are still relatively small compared to many others out there). Many thanks in advance.

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• Does SELinux make Redhat more secure?

  - by vfclists

  Does SELinux make Redhat more secure? I can't remember the number of times when I have disabled SELinux because it kept frustrating my ability to get stuff running. Lots of times to there was no obvious reason why stuff wasn't working and I had to Google to discover why. Given that most casual users will disable or weaken security when it appears to get in the way, with the exclusion of serious, enterprisey Redhat users, is SELinux really useful? PS. Is there some tool that helps you log, track and manage SELinux issues across all applications? In spite of being an Ubuntu user I am a closet Fedora fan.

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• OpenVPN Permission Denied Error

  - by LordCover

  I am setting OpenVPN up, and I'm in the state of adding users. Details: Host System: Windows Server 2003 32-bit. Guest System: Ubuntu Linux (with OpenVPN installed already), actually I downloaded it from OpenVPN.Net. Virtualization: VMWare v7.0 Problem: I can access the Access Server web portal (on the port 5480), but when I login to http://host_ip:943/admin and enter my (correct) login info, it shows me a page saying that "You don't have enough permissions". I am the (root) user!!!! that is really weird!!! Note: if I enter wrong login it will denote an incorrect login, this means that I am logging in successfully but the problem comes after the login process. What I tried: I tried to create another user after (root) logging in to Linux Bash using (useradd) command, but the same resulted.

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• Which components should I invest in.. for a backup machine.

  - by Senthil

  I am a freelance developer. I have a PC, a laptop and an old testing and file server machine. I might add one or two in future. I want to have an on-site backup machine that can handle backups of ALL these machines - file backups, MySQL backups, backup of subversion repository, etc.. When building the machine, which components should I invest more in? Examples: The cabinet should have lots of room for expansion. Hard disk size should be large. But I guess hard disk speed need not be high (?) But other components like, RAM, PSU, Processor, Network card, Cooling, etc.. how much relative importance do these have in a backup machine? Which of these components should be high-end or large, and which ones need not be? Some Idea of the load: There will TBs of data. File backups and subversion repository backups will at least be done daily. MySQL backups done weekly. assume 3 machines at the moment and somewhere around 10 machines in the future.

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• How to embed word doc as background picture of an Access report using .EMF or equivalent ?

  - by iDevlop

  My company's standard paper has logo, address and all the details in the right margin with a vertical blue line. I have that as a word template. I want to have the same thing as the background of my Invoices report. I managed to do that 5 years ago by saving to EMF format (vector format, prints out nicely) and putting the file as the background of the report. Now my company is moving, and I need to change the address on my invoices, but I can't find out how I did to convert the word doc to EMF. Any suggestion ? By EMF or another process, but I want to avoid BMP, which is huge and does not print nicely. Thanks !

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• Strange strace and setuid behaviour: permission denied under strace, but not running normally.

  - by Autopulated

  This is related to this question. I have a script (fix-permissions.sh) that fixes some file permissions: #! /bin/bash sudo chown -R person:group /path/ sudo chmod -R g+rw /path/ And a small c program to run this, which is setuided: #include "sys/types.h" #include "unistd.h" int main(){ setuid(geteuid()); return system("/path/fix-permissions.sh"); } Directory: -rwsr-xr-x 1 root root 7228 Feb 19 17:33 fix-permissions -rwx--x--x 1 root root 112 Feb 19 13:38 fix-permissions.sh If I do this, everything seems fine, and the permissions do get correctly fixed: james $ sudo su someone-else someone-else $ ./fix-permissions but if I use strace, I get: someone-else $ strace ./fix-permissions /bin/bash: /path/fix-permissions.sh: Permission denied It's interesting to note that I get the same permission denied error with an identical setup (permissions, c program), but a different script, even when not using strace. Is this some kind of heureustic magic behaviour in setuid that I'm uncovering? How should I figure out what's going on? System is Ubuntu 10.04.2 LTS, Linux 2.6.32.26-kvm-i386-20101122 #1 SMP

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• Safari Private Browsing and gmail

  - by John Smith

  I have two gmail accounts. If I follow the following steps then Safari will not let me log in to any other gmail account Go the gmail, log in as user1 Enable Private browsing Go to one website Disable Private browsing Go to gmail and logout. At this point gmail will not let me switch to user2. I have to quit the whole browser before I get that option. Is there a way to fix this? I am not trying to open two gmail accounts at the same time. Just one after the other. As long as I do not enter Private Browsing mode between the two logins I can switch between account1 and account2. Also, I am not changing browser to Firefox

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• Running IE on OSX with WineBottler: Can't find wine?

  - by AP257

  So I want to run IE7 on OSX 10.6 with WineBottler. I saw it was possible to run IE on Mac with WineBottler, following these instructions. I installed WineBottler and IE7. All was looking good. However, when I tried to open IE7 from the Applications menu, I got an error message: "Can't find Wine. Wine is required to run this program." I then installed wine-devel from macports (which was a bit fiddly as I hit this problem and had to update a lot of dependencies, but it did eventually build). However, even after doing that, I'm still seeing the 'Can't find wine' error message whenever I try to open IE7 or WineBottler. Could anyone advise? Do I need to start wine running somehow?

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• Problems installing Windows 7 on Dell Inspiron 531 desktop

  - by wardedmocha

  Hello. I am having a problem installing Windows 7 on a Dell Inspiron 531 desktop. I got the setup to run and now it was trying to restart and now the computer just beeps. Two times a second, one right after the other. The beep is not like a key is being held down. And the computer isn't showing anything on the screen. edit: this is a computer I am trying to fix there where two blue screen errors that I know of. the first one had something to do with a display driver the second one was unknown

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• How to run Firefox jailed without serious performance loss?

  - by Vi

  My Firefox configuration is tricky: Firefox runs at separate restricted user account which cannot connect to main X server. Firefox uses Xvfb (virtual "headless" X server) as X server. x11vnc is running on that Xvfb. On the main X server there is vncviewer running that connect to this x11vnc On powerful laptop (Acer Extensa 5220) it seems to work more or less well, but on "Acer Aspire One" netbook it is slowish (on a background that firefox is loaded with lots of extensions). How to optimise this scheme? Requirements: Browser cannot connect to main X server. Browser should be in chroot jail (no "suid" scripts, readonly for many things) Browser should have a lot of features (like in AutoPager, NoScript, WoT, AdBlockPlus)

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• Recover data from a corrupted virtualbox vmdk file?

  - by Neth

  The power went out while I was doing a build on a VirtualBox machine, when I restarted the vmdk for the disk the vm was using was corrupted, apparently irrecoverably. I have been able to grep the 66GB vmdk file and it finds strings from the code I was working on that hadn't gotten in to subversion yet (yeah, yeah I know). But the strings are either in the shell history or what look to be strings inside object files. Any ideas for finding/recovering the source code? If it helps the vm was Linux, Fedora Core 10 on an ext3 filesystem. The host is an ubuntu 10.04_amd64 and has an ext4 filesystem.

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• Indexing text file content with command line query

  - by Drew Carlton

  I take daily notes in a plaintext file labeled with date in the YYYYMMDD format. These files are no more than 100 lines long, and are written in a blog style format. I'd like to be able search these files as if they were blog posts indexed by google, with some phrase query returning the most relevant/recent date filenames, with a snippet containing the relevant part. Ideally it would be something like this: #searchindex "laptop no sound" returns: 20100909.txt: ... laptop sound isn't working... 20100101.txt ... sound is too loud... debating what laptop to buy... and so on and so forth. I'm working on a linux platform (Debian with GNOME). I've looked at beagle and tracker, but they just seem complete overkill for what I want.

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• Choice of filesystem for GNU/Linux on an SD card

  - by gspr

  Hi. I have am embedded ARM-based system running on an SD card. It's currently Debian GNU/Linux using ext3 as filesystem. As I'm about to reinstall the system, I started wondering about changing to a more flash-friendly filesystem. I've heard about JFFS2, YAFFS2 and LogFS, and they all seem suited to the job. Which one would you recommend? Also, I've heard there have been a lot of ext4 improvements to better suit SSD disks; am I to interpret that as running ext4 should be just fine? What do I need to think especially about in that case? I guess the usage of the system is important. But for the sake of generality, imagine it'll do standard desktop stuff (even though it is infact a small ARM-based system). Thanks for any replies. Edit: Wikipedia tells me (in a "citation needed" statement) that Removable flash memory cards and USB flash drives have built-in controllers to perform wear leveling and error correction so use of a specific flash file system does not add any benefit. Thus, I'm leaning towards sticking with an ext filesystem.

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• Graphics Card Compatability

  - by Aaron

  I am a first time builder and while I have the basic understanding of how to put a computer together, one final thing eludes me. What are the requirements for instaling 2 or more graphics cards on a computer? Example: EVGA 015-P3-1589-AR GeForce GTX 580 (Fermi) FTW Hydro Copper 2 1536MB 384-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card ECS NGTX580-1536PI-F GeForce GTX 580 (Fermi) 1536MB 384-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card I am not planning on buying either of these cards in the near future. I simply am using them as an example because of the number of differences. As I understand it these two cards will work together (given the proper motherboard) because the only thing that matters is that they are both GeForce GTX 580. Is my assumption correct? If not, why?

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• Is it possible to upgrade HTC HD2 to Windows Mobile 7? [closed]

  - by Ladislav Mrnka

  I have HD2 over one year and I have to say it was pretty wrong purchase. Both HTC HW and MS OS (Windows Mobile 6.5) are somehow crappy. I had several crashes wich resulted in hard reset (no flashing and almost no additionally installed applications) and phone was under repair two times (2x replaced motherboard and 1x replaced dislay). After these reapirs at least HW works pretty well but OS is still bad. I would like to upgrade the phone to Windows Mobile 7. I'm not looking for some flashing (I already saw some guides). I'm ready to pay for upgrade to have it legal. Is it possible? Buying new phone just to have SW upgrade is ridiculous. Btw. My primary phone is iPhone 4 and I think on iPhone 3GS it is possible to upgrade OS iOS 4 so I would like to see similar possibility with Windows Mobile.

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• how to compare files/directories of 2 separate solaris boxes ?

  - by chz

  Hi Friends I have 2 solaris boxes and I need to check certain directories (on local filesystem and mounted nfs) to make sure that they match up on both boxes and to delete or move the other mismatches to elsewhere on the local filesystem. I investigated for unix commands like rsync, and tree but it appears that these commands are not supported on my Solaris boxes. What is the best approach to this problem with the least pain to solve it ? to use rsync, tree and then diff the outputs or find ? I have trouble limiting the find command to certain directories as there are mounted folders that contain too many xml files that I don't care to much in that directory. What's the find command to search multiple directory paths on a single find command. Thanks Sincerely

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