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• MonoDevelop in Linux -- Terminal Commands

  - by Sandeep Bansal

  Hi everyone, I want to make a C# app in Mono as it's the only programming language I'm mostly comfortable with. Anyway, ATI Drivers on Linux do not have a Fan control feature and therefore the cards to tend to heat up. For me I prefer to have a cooler card. What I want to do is run a command such as: aticonfig --pplib-cmd 'set fanspeed 0 70' In a application but I the thing is..How can I run that code so it works, I am currently running Ubuntu 10.04, and it does work in the terminal, but I want to implement it into an application. Thanks

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• terminal: where am I?

  - by sid_com

  Is there a variable or a function, which can tell me the actual position of the cursor? #!/usr/bin/env perl use warnings; use 5.012; use Term::ReadKey; use Term::Cap; use POSIX; my( $col, $row ) = GetTerminalSize(); my $termios = new POSIX::Termios; $termios->getattr; my $ospeed = $termios->getospeed; my $terminal = Tgetent Term::Cap { TERM => undef, OSPEED => $ospeed }; # some movement ... # at which position (x/y) is the cursor now?

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• IBM HS23 Blade Server (7875) onboard NIC driver for linux

  - by Igor Spivak

  I work with IBM HS23 Blade Server (7875). It's onboard NIC adapter is: Emulex OCl11104-F-X Virtual Fabric Adapter 2-port 10GB and 2-port 1GB LOM . I'm tryed to the following Linux OS with the server: 2.6.32-22-generic-pae #36-Ubuntu SMP. and discovered my OS has not proper Network drive installed (for the NIC adapter described above). After investigation I made, I discovered that the driver I need is "be2net" placed in "net" directory of the linux under the folder "be2net". I managed to download this driver with the latest package for my kernel. Driver info ("modinfo be2net" result) is as follows: --------------------------------------------------------------------------------------- filename: /lib/modules/2.6.32-22-generic-pae/kernel/drivers/net/benet/be2net.ko license: GPL author: ServerEngines Corporation description: ServerEngines BladeEngine2 10Gbps NICDriver 2.101.205 version: 2.101.205 srcversion: 199ADD251CB874C3727CC47 alias: pci:v000019A2d00000710sv*sd*bc*sc*i* alias: pci:v000019A2d00000701sv*sd*bc*sc*i* alias: pci:v000019A2d00000700sv*sd*bc*sc*i* alias: pci:v000019A2d00000221sv*sd*bc*sc*i* alias: pci:v000019A2d00000211sv*sd*bc*sc*i* depends: vermagic: 2.6.32-22-generic-pae SMP mod_unload modversions 586TSC parm: rx_frag_size:Size of a fragment that holds rcvd data. (uint) --------------------------------------------------------------------------------------- After starting linux, I get the following error: be2net 0000:16:00.x: Emulex OneConnect 10Gbps NIC (be3) initilization failed. I checked the same server with another Linux version (Red-Had 5.5.1.0) and the NICs worked properly, so seems there is no problem in HW. Also, on IBM or Emulex offical sites I managed to find drivers only for Red-Had and SUSE versions.

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• Recommended motherboard with hardware raid for Linux

  - by luison

  Hi. We want to setup an internal office server for testing jobs (LAMP), email and samba. Only about 5-10 users. We are also considering starting to virtualize, initially by a base Ubuntu Server with Xen or VMWare Open Source server. Our current system runs with a Linux Raid which has worked great but it's always been complicated to recover the boot sector when one the drives fail and therefore I would prefer using now a hardware raid instead, but ideally with some kind of software monitoring. For this reason and considering we don't want to spend a fortune a I would appreciate any comments on the following options. Motherboard with RAID with linux support... which could you recommend. Motherboard + Hardware Raid card... Adaptec does not seem to have great Linux suppport. 3Ware seems to have a tc soft controller which we've used on a hosting company, but hard to find here in Spain. HP Proliant type basic server, which? Dell Small Servers... any good for Linux? Thanks in advance for any feedback.

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• Install Linux Mint on PC without bootable CD

  - by crosenblum

  Unfortunately my PC's CD drive is not bootable; I have such a mixture of SATA and IDE drives, so until I have more money to redo my controller setup, I can't boot from any cd. Currently, I have a DVD burned with latest version of Linux Mint, and I have an USB drive with an old version of Mint. I have a partition ready to install Linx Mint into, but no idea how to install it, since I can only boot to my hard drive. I am totally unable to boot to CD, so that is definitely out. My main partition is WinXP Pro SP3. Is there software I can use to format my Linux partition, so that I can then just copy Mint over to that partition? Or is there a better way to install linux mint? I have to do it within Windows XP, since that's all that I can boot right now. I have considered Mint4Win, but that doesn't allow a full installation of Linux Mint. Any ideas?

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• Ensuring a repeatable directory ordering in linux

  - by Paul Biggar

  I run a hosted continuous integration company, and we run our customers' code on Linux. Each time we run the code, we run it in a separate virtual machine. A frequent problem that arises is that a customer's tests will sometimes fail because of the directory ordering of their code checked out on the VM. Let me go into more detail. On OSX, the HFS+ file system ensures that directories are always traversed in the same order. Programmers who use OSX assume that if it works on their machine, it must work everywhere. But it often doesn't work on Linux, because linux file systems do not offer ordering guarantees when traversing directories. As an example, consider there are 2 files, a.rb, b.rb. a.rb defines MyObject, and b.rb uses MyObject. If a.rb is loaded first, everything will work. If b.rb is loaded first, it will try to access an undefined variable MyObject, and fail. But worse than this, is that it doesn't always just fail. Because the file system ordering on Linux is not ordered, it will be a different order on different machines. This is worse because sometimes the tests pass, and sometimes they fail. This is the worst possible result. So my question is, is there a way to make file system ordering repeatable. Some flag to ext4 perhaps, that says it will always traverse directories in some order? Or maybe a different file system that has this guarantee?

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• Sync files between 2 remote computers using Linux terminal

  - by Eddy

  I want to be able to synchronise files between 2 remote computers in both directions. Say for example that I want to synchronise my /home/Documents directory with <username>@example.com:/home/Documents What's the easiest way to update the folders in both directions, so that new/updated files on my home computer get transferred to the remote computer, and new/updated files on the remote computer get transferred to my home computer?

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• How can I bridge a VM to a remote network?

  - by asciiphil

  I have a system running QEMU/KVM (via libvirt). One of its VMs needs to have a presence on a subnet that is not local to the VM host. I have a Linux system on the remote subnet. Is there a way to set up some sort of tunneled bridge to cause the VM to appear present on the remote system? This will be a temporary situation (hopefully just until the VM owner can configure their system) and network performance and long-term maintainability aren't really issues. To give some more concrete information: My VM host has IP address 192.168.54.155/24. The VM has IP address 192.168.65.71/24. I have a remote system at 192.168.65.254/24. Both the VM host and remote system are running Scientific Linux 6.5. I do not control the network or routing in between the VM host and remote system. I do not have access to the guest OS on the VM. I would like traffic to the VM's IP address to end up at the VM even though its host isn't directly connected to the appropriate network. I've tried using iproute2's tunnelling, but Linux won't let me add a tunnel to a bridge. I've considered using some sort of iptables mangling to route traffic over the tunnel and make the VM think it's on the right network, but I'm not sure whether there are better approaches. What's the best way to accomplish this hack?

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• Picking a linux compatible motherboard

  - by Chris

  Last time I bought a new computer (I build them myself) I got a motherboard that had really poor linux support for a long time. Specifically the audio. I had to wait months before the kernel supported the on board audio chipset. That is exactly the situation I'm trying to avoid this time around. I have some specific questions about "server motherboards" actually. I looked at a few models of server motherboards by intel, and some random models on newegg. I wasn't able to see much of a difference from regular desktop motherboard other than most had two sockets, and support for much more ram. These boards seem more popular with Linux users. Why? AMD and Intel both have server CPUs as well. Some question, what's the difference? To make this question more concrete, I was looking at this this motherboard. The main questions about it that I can't answer are: Can I get a motherboard without on board raid and audio? I wanted to get a hardware raid controller and a PCI audio card. I thought a server motherboard would be cheaper and not have these "extras", since who wants an audio card on a server? Where can I found out about Linux support for the components on this board? "Intel ICH10R", "Realtek ALC889", "Marvell 88E8056" I'm buying this computer to work as a Linux desktop for a lot of compiling, coding and audio/video work, but I don't want to rule out the possibility of installing windows and playing some games at one point. (even if the last game I got has been sitting in its box unopened for almost a year). Is it a good idea to buy a "server motherboard" and play games on it, or are desktop boards better value for this? The ultimate solution for me would be a motherboard that had GPL divers for onboard LAN, a single CPU socket, lots of PCI express and PCI. USB 3.0, and no fancy hard disk controllers since I'll be getting a separate one.

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• Grant a user access to directories shared by root (mod: 770)

  - by Paul Dinham

  I want to grant a user (username: paul) access to all directories shared by root with mod 770. I do it this way: groups root (here comes a list of groups in which root user is) usermod -a -G group1 paul usermod -a -G group2 paul usermod -a -G group3 paul ... All the 'group1', 'group2', 'group3' are seen in the group list of root user. However, after adding 'paul' to all groups above, he still can not write to directories shared by root user with mod 770. Did I do it wrongly?

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• Tunning scrolling in urxvt

  - by Ivan Petrushev

  Hello, I'm using rxvt-unicode version 9.06 at Ubuntu 9.10. I was used to aterm, where you can use SHIFT + up/down arrow to scroll the printed output with a line up or down. You can also use SHIFT + pgup/pgdown to scroll one screen up or down. In urxvt I can use the pgup/pgdown combination as well, but can't use the up/down arrow combination. It is very useful to be able to scroll by single lines. Do you have any idea how to enable the up/down arrow scrolling? This is my ~/.inputrc: set show-all-if-ambiguous on And this is my ~/.Xdefaults: URxvt*geometry:80x35 URxvt*transparent:true URxvt*shading:40 URxvt*saveLines:12000 URxvt*foreground:White URxvt*background:Blue URxvt*font: -*-terminus-*-*-*-*-14-*-*-*-*-*-*-* URxvt*color4:RoyalBlue URxvt*color12:RoyalBlue URxvt*scrollBar:true URxvt*scrollBar_right:false URxvt*scrollstyle:rxvt

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• Copying files with SSH

  - by Deniz Zoeteman

  I am trying to copy a file from my other computer, to another computer. (both running Ubuntu 9.10) So say: I've ssh'ed into the other computer; i 'cd' to the directory; and i entered cp File.zip /home/me/Desktop as file.zip is located in the directory i just used cd with. Now, it gives me the following error message: cannot create regular file '/home/me/Desktop': no such file or directory What do i have to do?

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• Iptables Forwarding problem

  - by ankit

  Hi all, I had initally asked question about sertting up my linux box for natting for my home network and was given suggestions in the thread here. Did not want to clutter the old question so starting a new one here. based on the earlier suggestions, i have come up with the following rules ... :PREROUTING ACCEPT [1:48] :OUTPUT ACCEPT [12:860] :POSTROUTING ACCEPT [3:228] -A POSTROUTING -o eth0 -j MASQUERADE COMMIT *filter :INPUT DROP [3:228] :FORWARD DROP [0:0] :OUTPUT DROP [0:0] -A INPUT -i lo -j ACCEPT -A INPUT -i eth0 -p icmp -j ACCEPT -A INPUT -i eth0 -p tcp -m tcp --dport 80 -j ACCEPT -A INPUT -i eth0 -p tcp -m tcp --dport 443 -j ACCEPT -A INPUT -i eth0 -p tcp -m tcp --dport 22 -j ACCEPT -A FORWARD -i eth1 -p icmp -j ACCEPT -A FORWARD -i eth1 -p tcp -m tcp --dport 80 -j ACCEPT -A FORWARD -i eth1 -p tcp -m tcp --dport 443 -j ACCEPT -A OUTPUT -p icmp -j ACCEPT -A OUTPUT -j ACCEPT COMMIT If you notice, i do have the proper MASQURADING rule and the proper FORWARD filter rule as well. However i am facing 2 problems On the linux box itself DNS resolving is not working the lan clients connected to the linux box, are still not able to get to internet. when i ping something from them, i see the DROP count in iptables INPUT rule increasing. now my question is, when i am pinging something from the lan client, how come it is being matched by the input chain ?! should it be in the forward chain ? Chain INPUT (policy DROP 20 packets, 2314 bytes) pkts bytes target prot opt in out source destination 99 9891 ACCEPT all -- lo any anywhere anywhere 0 0 ACCEPT icmp -- eth0 any anywhere anywhere 0 0 ACCEPT tcp -- eth0 any anywhere anywhere tcp dpt:http 0 0 ACCEPT tcp -- eth0 any anywhere anywhere tcp dpt:https 122 9092 ACCEPT tcp -- eth0 any anywhere anywhere tcp dpt:ssh Thanks ankit

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• Performance monitoring on Linux/Unix

  - by ervingsb

  I run a few Windows servers and (Debian and Ubuntu) Linux and AIX servers. I would like to continously monitor performance on these systems in order to easily identify bottlenecks as well as to have an overview of the general activity on the servers. On Windows, I use Windows Performance Monitor (perfmon) for this. I set up these counters: For bottlenecks: Processor utilization : System\Processor Queue Length Memory utilization : Memory\Pages Input/Sec Disk Utilization : PhysicalDisk\Current Disk Queue Length\driveletter Network problems: Network Interface\Output Queue Length\nic name For general activity: Processor utilization : Processor\% Processor Time_Total Memory utilization : Process\Working Set_Total (or per specific process) Memory utilization : Memory\Available MBytes Disk Utilization : PhysicalDisk\Bytes/sec_Total (or per process) Network Utilization : Network Interface\Bytes Total/Sec\nic name (More information on the choice of these counters on: http://itcookbook.net/blog/windows-perfmon-top-ten-counters ) This works really well. It allows me to look in one place and identify most common bottlenecks. So my question is, how can I do something equivalent (or just very similar) on Linux servers? I have looked a bit on nmon (http://www.ibm.com/developerworks/aix/library/au-analyze_aix/) which is a free performance monitoring tool developed for AIX but also availble for Linux. However, I am not sure if nmon allows me to set up the above counters. Maybe it is because Linux and AIX does not allow monitoring these exact same measures. Is so, which ones should I choose and why? If nmon is not the tool to use for this, then what do you recommend?

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• picking a linux compatable motherboard

  - by Chris

  Last time I bought a new computer (I build them myself) I got a motherboard that had really poor linux support for a long time. Specifically the audio. I had to wait months before the kernel supported the on board audio chipset. That is exactly the situation I'm trying to avoid this time around. I have some specific questions about "server motherboards" actually. I looked at a few models of server motherboards by intel, and some random models on newegg. I wasn't able to see much of a difference from regular desktop motherboard other than most had two sockets, and support for much more ram. These boards seem more popular with Linux users. Why? AMD and Intel both have server CPUs as well. Some question, what's the difference? To make this question more concrete, I was looking at this this motherboard. The main questions about it that I can't answer are: Can I get a motherboard without on board raid and audio? I wanted to get a hardware raid controller and a PCI audio card. I thought a server motherboard would be cheaper and not have these "extras", since who wants an audio card on a server? Where can I found out about Linux support for the components on this board? "Intel ICH10R", "Realtek ALC889", "Marvell 88E8056" I'm buying this computer to work as a Linux desktop for a lot of compiling, coding and audio/video work, but I don't want to rule out the possibility of installing windows and playing some games at one point. (even if the last game I got has been sitting in its box unopened for almost a year). Is it a good idea to buy a "server motherboard" and play games on it, or are desktop boards better value for this? The ultimate solution for me would be a motherboard that had GPL divers for onboard LAN, a single CPU socket, lots of PCI express and PCI. USB 3.0, and no fancy hard disk controllers since I'll be getting a separate one.

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• Get Illegal Instruction error when booting Linux in VirtualBox, works fine when booted directly

  - by rkjnsn

  I have a computer on which I am dual booting Windows 7 and Gentoo Linux (both 64-bit). I want to be able to load up my Linux installation in a VM while I am booted into Windows. I have installed VirtualBox and followed the instructions for creating a raw disk VMDK. When I start the VM, Linux starts booting, but then fails with the following error when unlocking my root partition: truecrypt[441] trap invalid opcode ip:373615538e0 sp:3dd0e0dfb60 error:0 in libpixman-1.so.0[373614d6000+8d000] Everything works fine when I boot into Linux directly. What could cause an illegal instruction to be hit in libpixman only when booting in VirtualBox? Update: As a troubleshooting step, I recompiled pixman without "-march", and no longer get an illegal instruction error in that library. (The boot fails in the same spot with the same error in a different library, however.) How can I determine the specific opcode that isn't working in VirtualBox so I can disable it in my CFLAGS without having to disable all CPU-specific optimizations? I am still confused as to why there would be any user-mode instruction that would fail to work in a VM. Is this a known limitation? My CPU is an Intel Core i7 3720QM, and I have hardware virtualization support enabled.

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• Setting up a Network Bridge on Linux VM (Windows 7 Host)

  - by GrandAdmiral

  I would like to use NetEm to simulate a low bandwidth environment while testing an Internet-connected device. My plan is to setup a bridge in a Linux VM (Linux Mint 13) on a Windows 7 host. Unfortunately I'm having trouble setting up the bridge. Then I can use NetEm in the Linux VM to limit the bandwidth to an external device. I went with the following script: ifconfig eth0 0.0.0.0 promisc up ifconfig eth1 0.0.0.0 promisc up Then create the bridge and bring it up: brctl addbr br0 brctl setfd br0 0 brctl addif br0 eth0 brctl addif br0 eth1 dhclient br0 ifconfig br0 up When I run that script, I see the following warning: Rather than invoking init scripts through /etc/init.d, use the service(8) utility, e.g. service smbd reload Since the script you are attempting to invoke has been converted to an Upstart job, you may also use the reload(8) utility, e.g. reload smbd The device connecting to the bridge is able to obtain an IP Address, but it can only ping the IP Address of the bridge (both are 10.2.32.xx). Then after a few minutes, other parts of our network go down. I'm not sure why, but once I kill the bridge the network is fine. Is it possible to setup a network bridge in a Linux VM? Do I need to do something else with the dhclient br0 part of the script? By the way, I'm using VirtualBox. The wired connection is eth0 and the wireless connection is eth1. The wired connection is connecting to the device and the wireless connection is going to the network. Both adapters are set up as bridged adapters with promiscuous mode set to "allow all".

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• how to switch to another window when Ctrl + B not works for tmux?

  - by hugemeow

  as we all know tmux is quite nice tool, but there is some scenerios that Ctrl + B cannot be used for example: i sshd to server A, and now i connect to A's tmux pty, so Ctrl + B is captured by server A. then i ssh to server B from server A, and there is also tmux running on Server B, this time, Ctrl + B only works for server A, and cannot be used by server B, so if i want to switch windows for server B, what should i do then?

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• Why do hosts prefer Linux to Windows Server?

  - by iconiK

  So far I see a HUGE majority of hosts provide only Linux shared hosting, providing Windows only to VPS (or even to only dedicated servers). Why is it so? While Windows is a lot more expensive than Linux (though it depends on a lot of factors, not just initial and support license cost), it also provides ASP.NET, IIS and of course, Microsoft SQL Server. I know in the past it might have been because of cPanel being Linux only but now they have a Windows version. But still, why is Linux predominantly used on shared hosting? PHP works on both systems. IIS can be (and probably is) faster. MySQL runs on both systems as well. cPanel has a Windows version. Python, Perl, Ruby, all run on Windows as well. You even have MS SQL Server Express, which I find more superior than MySQL in both speed and features. Access is there for low usage requirements, as is SQLite (which is so great for quick small stuff). And with PowerShell you have a good alternative to the Unix shell. EDIT: I am looking for common reasons, I realize each hosting company (and/or it's clients) may have different needs. This becomes very important when you get to VPS or Cloud which give you a full operating system to use.

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• Downloading a large site with wget

  - by Evan Gill

  Hi, I'm trying to mirror a very large site but wget never seems to finish properly. I am using the command: wget -r -l inf -nc -w 0.5 {the-site} I have downloaded a good portion of the site, but not the whole thing. The content does not change fast enough to bother using time-stamping. After running overnight, this message appears: File `{filename}.html' already there; not retrieving. File `{filename}.html' already there; not retrieving. File `{filename}.html' already there; not retrieving. File `{filename}.html' already there; not retrieving. Killed does anyone know what is happening and how I can fix it?

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• Curl authentication

  - by Jack Humphries

  I am trying to download a file with cURL from a password protected directory on my site. It is not working. Instead of the downloading the requested file, it downloads a HTML file that says, "Authentication Required!" I'm not sure what the problem is. I've tried both of these (with the same result). The username and password are correct (and if the link below is used in a web browser, the file downloads successfully). 1) The username and password are included as part of the URL. curl https://username:[email protected]/auth/file.dmg --O /file.dmg; 2) The username and password are included as an option. curl -u username:wordpass.1 https://www.example.com/auth/file.dmg --O /file.dmg;

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• WMII Terminal Width of 80 Columns for xterm (colrules)

  - by BCable

  I'm trying to get WMII to split horizontally at 80 columns for xterm, but I'm only seeing a way to do this via percentage. It would be nice to be able to set it by something other than percentage for various resolutions, but if I have to deal with that I will. The problem is that even percentages don't work at my resolution (1366x768). 47+47 in /colrules yields 79 characters and 48+48 yields 81 characters. As far as I can tell, there is no decimal system allowed so I could do 47.5 for instance. I came from Ion3 and I'm used to using 80 column terminals, resizable by the keyboard, to get a reasonable cut off point for VIM when I'm coding. I would just settle with using the mouse, but WMII seems to be much more fluid than Ion3, so I would have to do it a LOT, which sounds annoying. Any ideas?

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• Routing table on Linux not respected

  - by MRHaarmann

  I have a very specific problem, building a Linux VPN endpoint (with external VPN Gateway), which should route certain networks over the tunnel, others via default gateway. The Linux VPN should do a NAT on the outgoing connections for the VPN peers. Setup is as following: Internet gateway LAN 192.168.25.1/24 VPN Gateway LAN 10.45.99.2/24 (VPN tunnel 10.45.99.1 to net 87.115.17.40/29, separate connection to Internet) Linux VPN Router eth0 192.168.25.71/24 eth0:503 10.45.99.1/24 Default 192.168.25.1 route to 87.115.17.40/29 via 10.45.99.2 (send_redirects disabled, ip_forward enabled) Linux clients (multiple): eth0 192.168.25.x/24 Default 192.168.25.1 route to 87.115.17.40/29 via 192.168.25.71 Ping to the machines via tunnel from the VPN Router is working. Now I want to establish a routing from my clients over the VPN gateway and the client packet gets routed to 192.168.25.1 ! traceroute output shows the packets get routed to 192.168.25.71, but then to 192.168.25.1. So the route is not respected in forward ! IPTables and Routing: ip route show 87.115.17.40/29 via 10.45.99.2 dev eth0 10.45.99.0/24 dev eth0 proto kernel scope link src 10.45.99.1 192.168.25.0/24 dev eth0 proto kernel scope link src 192.168.25.71 default via 192.168.25.1 dev eth0 iptables -A INPUT -i eth0:503 -j REJECT iptables -t nat -A POSTROUTING -o eth0:503 -j MASQUERADE iptables -A FORWARD -i eth0:503 -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -s 192.168.25.0/24 -o eth0:503 -j ACCEPT So what is wrong with my setup ? The route is chosen correctly from localhost, but all the clients get forwarded to the Internet GW. thanks for helping, Marcus

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• Linux virtualization choices with graphic acceleration / video card support

  - by Urbn

  I am in the process of building a new desktop machine for work and fun. I am looking to run a undecided flavor of Linux (guessing Ubuntu) as my primary OS and several Windows installs with a Windows 7 install for .net development and gaming as virtualized environments. From my previous experiences with virtualization software in Linux I was never able to find an application that offered descent video card support / graphic acceleration etc. to be capable of playing any games within one of the virtualized environments. And since I will be investing quite a bit of money into this system for gaming I would naturally want to find the best option available to achieve this setup. So Onto my question: Is there any virtualization software available for Linux that has full video card support, graphic acceleration and capable of taking advantage of everything the video cards have to offer within the virtualized environments? Or am I stuck with running Windows 7 as my primary OS and using virtualization for Linux and the other OS's? Also I have no preference on open/closed source and price range would be up to $175.00 to support at least 3 virtualized environments.

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• Parallel processing slower than sequential?

  - by zebediah49

  EDIT: For anyone who stumbles upon this in the future: Imagemagick uses a MP library. It's faster to use available cores if they're around, but if you have parallel jobs, it's unhelpful. Do one of the following: do your jobs serially (with Imagemagick in parallel mode) set MAGICK_THREAD_LIMIT=1 for your invocation of the imagemagick binary in question. By making Imagemagick use only one thread, it slows down by 20-30% in my test cases, but meant I could run one job per core without issues, for a significant net increase in performance. Original question: While converting some images using ImageMagick, I noticed a somewhat strange effect. Using xargs was significantly slower than a standard for loop. Since xargs limited to a single process should act like a for loop, I tested that, and found it to be about the same. Thus, we have this demonstration. Quad core (AMD Athalon X4, 2.6GHz) Working entirely on a tempfs (16g ram total; no swap) No other major loads Results: /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 1 convert -auto-level real 0m3.784s user 0m2.240s sys 0m0.230s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 2 convert -auto-level real 0m9.097s user 0m28.020s sys 0m0.910s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 10 convert -auto-level real 0m9.844s user 0m33.200s sys 0m1.270s Can anyone think of a reason why running two instances of this program takes more than twice as long in real time, and more than ten times as long in processor time to complete the same task? After that initial hit, more processes do not seem to have as significant of an effect. I thought it might have to do with disk seeking, so I did that test entirely in ram. Could it have something to do with how Convert works, and having more than one copy at once means it cannot use processor cache as efficiently or something? EDIT: When done with 1000x 769KB files, performance is as expected. Interesting. /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 1 convert -auto-level real 3m37.679s user 5m6.980s sys 0m6.340s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 1 convert -auto-level real 3m37.152s user 5m6.140s sys 0m6.530s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 2 convert -auto-level real 2m7.578s user 5m35.410s sys 0m6.050s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 4 convert -auto-level real 1m36.959s user 5m48.900s sys 0m6.350s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 10 convert -auto-level real 1m36.392s user 5m54.840s sys 0m5.650s

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