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  • Why I have to redeclare a virtual function while overriding [C++]

    - by Neeraj
    #include <iostream> using namespace std; class Duck { public: virtual void quack() = 0; }; class BigDuck : public Duck { public: // void quack(); (uncommenting will make it compile) }; void BigDuck::quack(){ cout << "BigDuckDuck::Quack\n"; } int main() { BigDuck b; Duck *d = &b; d->quack(); } Consider this code, the code doesn't compiles. However when I declare the virtual function in the subclass, then it compiles fine. The compiler already has the signature of the function which the subclass will override, then why a redeclaration is required? Any insights.

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  • Find which config file Apache uses to find virtual host

    - by eje211
    I have a rather complicated Apache setup: some config files have to be manually written and some have to be automatically generated. So far, I've had no problems. But now, I've just tried to set a site at: newsubdomain.mydomain.com and Apache directs it to the data for: www.someotherdomain.com I've looking into all the many config files and can't find anything wrong. All is pointing where it should and no definitions, as far as I can tell, overlap. So what I'm wondering is: is there a way to see which config files or config instructions Apache is using to match a URL to a directory? Tanks.

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  • Large virtual memory size of ElasticSearch JVM

    - by wfaulk
    I am running a JVM to support ElasticSearch. I am still working on sizing and tuning, so I left the JVM's max heap size at ElasticSearch's default of 1GB. After putting data in the database, I find that the JVM's process is showing 50GB in SIZE in top output. It appears that this is actually causing performance problems on the system; other processes are having trouble allocating memory. In asking the ElasticSearch community, they suggested that it's "just" filesystem caching. In my experience, filesystem caching doesn't show up as memory used by a particular process. Of course, they may have been talking about something other than the OS's filesystem cache, maybe something that the JVM or ElasticSearch itself is doing on top of the OS. But they also said that it would be released if needed, and that didn't seem to be happening. So can anyone help me figure out how to tune the JVM, or maybe ElasticSearch itself, to not use so much RAM. System is Solaris 10 x86 with 72GB RAM. JVM is "Java(TM) SE Runtime Environment (build 1.7.0_45-b18)".

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  • Performance of Virtual machines on very low end machines

    - by TheLQ
    I am managing a few cheap servers as my user base isn't large enough to get much more powerful servers. I also don't have the money lying around to invest in a server to prepare for the larger user base. So I'm stuck with the old hardware I have. I am toying with the idea of virtualizing all the current OS's with most likely VMware vSphere Hypervisor (AKA ESXi) Xen (ESXi has too strict of an HCL, and my hardware is too old). Big reasons for doing so: Ability to upgrade and scale hardware rapidly - This is most likely what I'll be doing as I distribute services, get a bigger server, centralize (electricity bills are horrible), distribute, get a bigger server, etc... Manually doing this by reinstalling the entire OS would be a big pain Safety from me - I've made many rookie mistakes, like doing lots of risky work on a vital production server. With a VM I can just backup the state, work on my machine, test, and revert if necessary. No worries, and no OS reinstallation Safety from other factors - As I scale servers might go down, and a backup VM can instantly be started. Various other reasons. However the limiting factor here is hardware. And I mean very depressing hardware. The current server's run off of a Pentium 3 and 4, and have 512 MB and 768 MB RAM respectively (RAM can be upgraded soon however). Is the Virtualization layer small enough to run itself and a Linux OS effectively? Will performance be acceptable (50% CPU overhead for every operation isn't acceptable)? Does it leave enough RAM for the Linux OS? Is this even feasible?

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  • Virtual (ESXi4) Win 2k8 R2 server hangs when adding role(s)

    - by Holocryptic
    I'm trying to provision a 2k8r2 Enterprise server in ESXi4. The OS installation goes fine, VMware tools, adding to domain, updates. All the basic stuff before you start adding Roles and Features. I've had this happen on two attempts already, and I'm not sure where the problem might be. I don't think it's hardware, because I have another 2k8r2 Standard server that's running fine. The only real difference is the install media. The server that's working was installed using a trial ISO and license. The one I'm having problems with is a full MAK installation. When I go to add a Role (the last case was Application Server) it gets all the way to "collecting installation results" before it hangs. CPU utilization in the vSphere client shows little spikes of activity with flatlines inbetween, but the whole console is locked up. The only way to release it is to power off and bring it back up. When you go to look at the added roles after bringing it back up, it shows that it is installed, but I don't trust that something didn't get wedged in all of that. The first install I did was with Thin Disk provisioning. The second attempt was with regular disk provisioning. In both cases 4GB of RAM, 2 vCPUs. VMware host is a HP Proliant DL380 G6, RAID-1 OS, RAID-5 data volume. 12 GB RAM. Has anyone else had this problem, or know where I should start poking around?

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  • How to configure a gateway virtual machine

    - by user225706
    I have a VM-host configured with eth0 (10.145.73.207) and eth1(192.168.101.231), and three VMs connecting the Internet through NAT, with the default gateway of 192.168.122.1. Now I want to configure VM2 as a gateway. I added eth0 (192.168.122.63) and eth1 (172.16.1.109) for VM2. It can connect to the Internet with each of them. I changed the default gateway of VM1 from 192.168.122.1 to 192.168.122.63. However, when I traceroute google.com on VM1, it shows that the packet only reaches 192.168.122.63, no further. Any help is appreciated. Thanks.

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  • Virtual terminal with at least 16bit color?

    - by trusktr
    It's 2013 and there should be terminals with more than 256 colors by now (you'd think). Are there any terminals with more than 8bit colors (usually from 8 bit we jump to 16bit) to use with linux? Ideally, I'd like to have a linux terminal with 32bit colors for the foreground and background of each character. So, the functionality would be the same, with escape sequences, but just more of them (or something like that?).

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  • My HiperV Virtual Server stops with critical error.

    - by Svisstack
    Hello, I on microsoft hyper v create a server, i installing on it linux debian, but while instalation this server stopped with critical error and if I start it, he stops after approximaly 1 minute. How to debug it? Where i can find information about this critical error because in a events viewer I can't find any information about it.

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  • How to enable Ipv6 on my ubunutu 11.04 virtual machine

    - by liv2hak
    I have installed 3 VM's on my PC.(Ubuntu 11.04).I want to setup an IPV6 network to review and test some of the IPV6 tools like NDPMonitor.(monitors ICMP messages of Neighbour Discovery Protocol.) IP v6 addresses are as follows. linux_router - fe80::a00:27ff:fed5:f7e9/64 labhack1 - fe80::a00:27ff:fed2:8bd1/64 labhack2 - fe80::a00:27ff:fed7:2f2d/64 The below commands have been run on both linux_router and labhack1. sudo ip r a 2001:468:181:f100::/64 dev eth0 sudo vim /etc/radvd.conf /file looks like below./ interface eth0 { AdvSendAdvert on; /*means that we are sending out advertisments.*/ MinRtrAdvInterval 5; /*these options control how often advertisments are sent*/ MaxRtrAdvInterval 15; /*these are not mandatory but valueable settings.*/ prefix fe80::a00:27ff::/64 { AdvOnLink on; /*Says to the host everyone sharing this prefix is on the sam local link as you.*/ AdvAutonomous on; /*Says to a host: "Use this prefix to autoconfigure your address"*/ }; }; sudo sysctl -w net.ipv6.conf.all.forwarding=1 I try to do a ping6 -I eth0 fe80::a00:27ff:fed5:f7e9 I get Destination unreachable: Address unreachable.I am not sure what I am doing wrong here.I am a beginner at linux administration.Basically I think I am missing whatever is analogous to physically connecting VM's.Any help that would point me in the right direction would be greatly appreciated.

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  • Apache server configuration name resolution (virtual host naming + security)

    - by Homunculus Reticulli
    I have just setup a minimal (hopefully secure? - comments welcome) apache website using the following configuration file: <VirtualHost *:80> ServerName foobar.com ServerAlias www.foobar.com ServerAdmin [email protected] DocumentRoot /path/to/websites/foobar/web DirectoryIndex index.php # CustomLog with format nickname LogFormat "%h %l %u %t \"%r\" %>s %b" common CustomLog "|/usr/bin/cronolog /var/log/apache2/%Y%m.foobar.access.log" common LogLevel notice ErrorLog "|/usr/bin/cronolog /var/log/apache2/%Y%m.foobar.errors.log" <Directory /> AllowOverride None Order Deny,Allow Deny from all </Directory> <Directory /path/to/websites/> Options -Indexes FollowSymLinks MultiViews AllowOverride None Order allow,deny allow from all </Directory> </VirtualHost> I am able to access the website by using www.foobar.com, however when I type foobar.com, I get the error 'Server not found' - why is this? My second question concerns the security implications of the directive: <Directory /path/to/websites/> Options -Indexes FollowSymLinks MultiViews AllowOverride None Order allow,deny allow from all </Directory> in the configuration above. What exactly is it doing, and is it necessary?. From my (admitedly limited) understanding of Apache configuration files, this means that anyone will be able to access (write to?) the /path/to/websites/ folder. Is my understanding correct? - and if yes, how is this not a security risk?

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  • `:Zone.Identifier` files keep on appearing in Windows XP virtual machine

    - by Jonathan Reno
    I have a Windows XP Home Edition guest and a Linux Mint 13 host. I use VirtualBox and the ~/Public directory is shared with the guest. It sometimes happens that I use IE on the guest system to download files (until I get a better Windows browser). All of the downloaded files go the the L:\ drive (the ~/Public directory). When they are finished downloading, Windows Explorer adds a :Zone.Identifier file for each file I download. When I extract a downloaded ZIP archive on the guest (on drive L:\), Windows creates a :Zone.Identifier file for every file in the extracted directory. This even occurs if I use the host to move a file to the ~/Public directory. The shared ~/Public directory is on an ext4 partition and the colon character is supposed to be illegal in file names in Windows, but not on the ext4 partition. Is there any way to stop Windows from putting all this rubbish on my filesystem? (I might have to create a shell script to clean up after Windows' act.) Here is what I see in Windows Explorer: By the way, if I were running a Mac OS X host (where colons are illegal file name characters) this would be even more horrendous.

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  • how to optimize virtual box shared folders

    - by Nrew
    This is really pissing me off. No matter how much memory I put into the guest os(windows xp). It still hangs for about 365 days before you can access the file you want to access from the shared folder. What do I do to make things faster? Because after it hangs and not respond for 365 days. It will do it again for another 250 days. Ive even set the shared folder to permanent. This is a fairly decent machine: 2.50ghz processor(x64 architecture, but I have only 2Gb of memory so my host os is just 32 bit windows 7) hdd has much space left: 156 Gb free of 250Gb

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  • linux hardware raid 10 / lvm / virtual machine partition alignment and filesystem optimization

    - by Jason Ward
    I've been reading everything I can find about partition alignment and filesystem optimization (ext4 and xfs) but still don't know enough to be confident in setting up my current configuration. My remaining confusion comes from the LVM layer and if I should use raid parameters on the filesystem in guest os'es. My main questions are: When I use 'pvcreate --dataalignment' do I use the stripe-width as calculated for a filesystem on RAID (128kB for ext4 in my situation), the Stripe size of the RAID set (256kB), something else altogether, or do I not need this? When I create ext2/3/4 or xfs filesystems in guests on the Logical Volumes, should I add the settings for the underlying RAID (e.g. mkfs.ext4 -b 4096 -E stride=64,stripe-width=128)? Does anyone see any glaring errors in my set up below? I'm running some benchmarks now but haven't done enough to start comparing results. I have four drives in RAID 10 on a 3ware 9750-4i controller (more details on the settings below) giving me a 6.0TB device at /dev/sda. Here is my partition table: Model: LSI 9750-4i DISK (scsi) Disk /dev/sda: 5722024MiB Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 1.00MiB 257MiB 256MiB ext4 BOOTPART boot 2 257MiB 4353MiB 4096MiB linux-swap(v1) 3 4353MiB 266497MiB 262144MiB ext4 4 266497MiB 4460801MiB 4194304MiB Partition 1 is to be the /boot partition for my xen host. Partition 2 is swap. Partition 3 is to be the root (/) for my xen host. Partition 4 is to be (the only) physical volume to be used by LVM (for those who are counting, I left about 1.2TB unallocated for now) For my Xen guests, I usually create a Logical Volume of the needed size and present it to the guests for them to partition as needed. I know there are other ways of handling that but this method works best for my situation. Here's the hardware of interest on my CentOS 6.3 Xen Host: 4x Seagate Barracuda 3TB ST3000DM001 Drives (sector size: 512 logical/4096 physical) 3ware 9750-4i w/BBU (sector size reported: 512 logical/512 physical) All four drives make up a RAID 10 array. Stripe: 256kB Write Cache enabled Read Cache: intelligent StoreSave: Balance Thanks!

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  • Oracle Virtual Server OEL vm fails to start - kernel panic on cpu identify

    - by Towndrunk
    I am in the process of following a guide to setup various oracle vm templates, so far I have installed OVS 2. 2 and got the OVM Manager working, imported the template for OEL5U5 and created a vm from it.. the problem comes when starting that vm. The log in the OVMM console shows the following; Update VM Status - Running Configure CPU Cap Set CPU Cap: failed:<Exception: failed:<Exception: ['xm', 'sched-credit', '-d', '32_EM11g_OVM', '-c', '0'] => Error: Domain '32_EM11g_OVM' does not exist. StackTrace: File "/opt/ovs-agent-2.3/OVSXXenVMConfig.py", line 2531, in xen_set_cpu_cap run_cmd(args=['xm', File "/opt/ovs-agent-2.3/OVSCommons.py", line 92, in run_cmd raise Exception('%s => %s' % (args, err)) The xend.log shows; [2012-11-12 16:42:01 7581] DEBUG (DevController:139) Waiting for devices vtpm [2012-11-12 16:42:01 7581] INFO (XendDomain:1180) Domain 32_EM11g_OVM (3) unpaused. [2012-11-12 16:42:03 7581] WARNING (XendDomainInfo:1907) Domain has crashed: name=32_EM11g_OVM id=3. [2012-11-12 16:42:03 7581] ERROR (XendDomainInfo:2041) VM 32_EM11g_OVM restarting too fast (Elapsed time: 11.377262 seconds). Refusing to restart to avoid loops .> [2012-11-12 16:42:03 7581] DEBUG (XendDomainInfo:2757) XendDomainInfo.destroy: domid=3 [2012-11-12 16:42:12 7581] DEBUG (XendDomainInfo:2230) Destroying device model [2012-11-12 16:42:12 7581] INFO (image:553) 32_EM11g_OVM device model terminated I have set_on_crash="preserve" in the vm.cfg and have then run xm create -c to get the console screen while booting and this is the log of what happens.. Started domain 32_EM11g_OVM (id=4) Bootdata ok (command line is ro root=LABEL=/ ) Linux version 2.6.18-194.0.0.0.3.el5xen ([email protected]) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)) #1 SMP Mon Mar 29 18:27:00 EDT 2010 BIOS-provided physical RAM map: Xen: 0000000000000000 - 0000000180800000 (usable)> No mptable found. Built 1 zonelists. Total pages: 1574912 Kernel command line: ro root=LABEL=/ Initializing CPU#0 PID hash table entries: 4096 (order: 12, 32768 bytes) Xen reported: 1600.008 MHz processor. Console: colour dummy device 80x25 Dentry cache hash table entries: 1048576 (order: 11, 8388608 bytes) Inode-cache hash table entries: 524288 (order: 10, 4194304 bytes) Software IO TLB disabled Memory: 6155256k/6299648k available (2514k kernel code, 135548k reserved, 1394k data, 184k init) Calibrating delay using timer specific routine.. 4006.42 BogoMIPS (lpj=8012858) Security Framework v1.0.0 initialized SELinux: Initializing. selinux_register_security: Registering secondary module capability Capability LSM initialized as secondary Mount-cache hash table entries: 256 CPU: L1 I Cache: 64K (64 bytes/line), D cache 16K (64 bytes/line) CPU: L2 Cache: 2048K (64 bytes/line) general protection fault: 0000 [1] SMP last sysfs file: CPU 0 Modules linked in: Pid: 0, comm: swapper Not tainted 2.6.18-194.0.0.0.3.el5xen #1 RIP: e030:[ffffffff80271280] [ffffffff80271280] identify_cpu+0x210/0x494 RSP: e02b:ffffffff80643f70 EFLAGS: 00010212 RAX: 0040401000810008 RBX: 0000000000000000 RCX: 00000000c001001f RDX: 0000000000404010 RSI: 0000000000000001 RDI: 0000000000000005 RBP: ffffffff8063e980 R08: 0000000000000025 R09: ffff8800019d1000 R10: 0000000000000026 R11: ffff88000102c400 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffffffff805d2000(0000) knlGS:0000000000000000 CS: e033 DS: 0000 ES: 0000 Process swapper (pid: 0, threadinfo ffffffff80642000, task ffffffff804f4b80) Stack: 0000000000000000 ffffffff802d09bb ffffffff804f4b80 0000000000000000 0000000021100800 0000000000000000 0000000000000000 ffffffff8064cb00 0000000000000000 0000000000000000 Call Trace: [ffffffff802d09bb] kmem_cache_zalloc+0x62/0x80 [ffffffff8064cb00] start_kernel+0x210/0x224 [ffffffff8064c1e5] _sinittext+0x1e5/0x1eb Code: 0f 30 b8 73 00 00 00 f0 0f ab 45 08 e9 f0 00 00 00 48 89 ef RIP [ffffffff80271280] identify_cpu+0x210/0x494 RSP ffffffff80643f70 0 Kernel panic - not syncing: Fatal exception clear as mud to me. are there any other logs that will help me? I have now deployed another vm from the same template and used the default vm settings rather than adding more memory etc - I get exactly the same error.

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  • Mounting an FTP as a virtual disk (FTPDrive analogue)

    - by axk
    FTPDrive has been a great utility for me, but it does not support 64bit Windows 7. The feature of FTPDrive that is useful for me is accesing files from an FTP as local files without pre-downloading so that I can preview and watch movies from a local FTP server without waiting for a full movie to get downloaded first. Do you know of any software which allows accessing files over FTP without pre-downloading? Thanks!

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  • virtual machines and cryptography

    - by Unknown
    I suspect I'm a bit offtopic with the site mission, but it seems me more fitting for the question than stackoverflow i'm in preparing to create a vm with sensible data (personal use, it will be a web+mail+... appliance of sorts), i'd like to protect the data even with cryptography; the final choice have to be cross-platform for the host basically, I have to choose between guest system-level cryptography (say, dm-crypt or similar) or host level cryptography with truecrypt. do you think that the "truecrypt-volume contained virtualized disks" approach will hit the i/o performance of the vm badly (and therefore dm-crypt like approaches into the vm would be better), or is it doable? I'd like to protect all the guest data, not only my personal data, to be able to suspend the vm freely without worrying for the swap partition, etc

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  • Virtual PC lost parent disk for differential vhd

    - by SeeR
    2 years ago I had that brilliant idea to create base Windows XP disk which all of my VM with XP will use. Of course it ended that I had only one VM with XP :-). Today I needed to make some free space on my HDD so I found one not used VM named "Windows XP" which had only 5GB. I deleted it as fast as possible :-) and of course I used shift to not use "Recycle bin". Now when I want to run my XP VM I have following error: "One of the parent hard disks of ... is missing." It's not a problem for me as soon as I can restore files from this differential vhd that I have right now. So: I have differential disk with files I need I don't have parent disk My question is: How can I restore files from this differential hvd?

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  • My HyperV Virtual Server stops with critical error.

    - by Svisstack
    Hello, I on microsoft hyper v create a server, i installing on it linux debian, but while installation this server stopped with critical error and if I start it, he stops after approximaly 1 minute. How to debug it? Where i can find information about this critical error because in a events viewer I can't find any information about it.

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  • How to specify a different ip address in virtual box guest os

    - by Nrew
    I am using Windows 7 as the host. And xp as guest. I've already check out this site: http://forums.virtualbox.org/viewtopic.php?f=3&t=17232 But the info is not complete. What do I need to set here, so that the guest would have another IP Address but can still connect to the internet. Because what I'm trying to accomplish here is to be able to try Team Viewer or Cross loop. With the host os and guest os. Because I only have one computer.

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  • Virtual OS using same Wallpaper as Host

    - by Jeff
    Greetings, I'm running a guest Linux OS on top of Windows XP, which rotates its wallpapers using the PowerToy Wallpaper Changer. I'm hoping for a way for my guest OS to somehow detect which wallpaper the host is using, and automatically switch to it. Why? Because if I run my guest OS in seamless mode and have transparent windows, I want the transparent background to match the host OS. It looks nice that way :). A couple tidbits of relevant information: Guest OS is Peppermint Ice (Ubuntu based) Host OS is Windows XP VirtualBox as virtualization software I realize this is somewhat breaking borders between the host and the guest, but I want my pretty rotating wallpaper! I'm guessing there is a way using scripts and shared folders or something similar, if not by means of just querying the host OS.

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  • Alias a Virtual Directory or Application as Root on IIS 7

    - by manyxcxi
    Our current IIS setup as two applications running on different paths at (for example) http://server/sub-a and http://server/sub-b. I want to alias http://server/sub-a as root so that just going to http://server/ will bring up the contents of sub-a. The problem I face is that when I initially set up a ReverseProxy it negatively affected http://server/sub-b. I know this is a fairly common problem- how have you solved it? 99.9% of my experience is with Apache, so I feel a tad lost in the GUI world of IIS.

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