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• Setup staging with multiple SVN

  - by Kapil Sharma

  We are a startup, setting new environments for product to be released soon. Planned server structure with planned release flow is as shown in below image It ideally have a local server (or Staging server, shown in green) in local office, without public IP address and Production Server (Red) at Amazon EC2. Both local and production server have there own SVN copy. Management here want to update production server with production SVN and without providing its access to developers (including freelancers/contract employees). So for developers, there is a Local SVN on local server. Another purpose of local SVN to keep a copy of code on local server, which is under our direct control. Although there are some technical concerns like how will code at local server will be updated from local SVN and commit on production SVN but bigger question is, is that structure correct? Major requirement remain don't provide production SVN access to developers. What are other possible options to achieve that? Another minor question, if suitable here, if above structure is correct, is it possible for a SVN checkout to get updated from one SVN (Local SVN) but commit to other (Production SVN)? If yes, How? edit An answer has been accepted but for bounty, I'm still looking for answer Is that structure correct? Its pros/Cons? Technical solution is already provided by accepted answer.

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• To Bit or Not To Bit

  - by Johnm

  'Twas a long day of troubleshooting and firefighting and now, with most of the office vacant, you face a blank scripting window to create a new table in his database. Many questions circle your mind like dirty water gurgling down the bathtub drain: "How normalized should this table be?", "Should I use an identity column?", "NVarchar or Varchar?", "Should this column be NULLABLE?", "I wonder what apple blue cheese bacon cheesecake tastes like?" Well, there are times when the mind goes it's own direction. A Bit About Bit At some point during your table creation efforts you will encounter the decision of whether to use the bit data type for a column. The bit data type is an integer data type that recognizes only the values of 1, 0 and NULL as valid. This data type is often utilized to store yes/no or true/false values. An example of its use would be a column called [IsGasoline] which would be intended to contain the value of 1 if the row's subject (a car) had a gasoline engine and a 0 if the subject did not have a gasoline engine. The bit data type can even be found in some of the system tables of SQL Server. For example, the sysssispackages table in the msdb database which contains SQL Server Integration Services Package information for the packages stored in SQL Server. This table contains a column called [IsEncrypted]. A value of 1 indicates that the package has been encrypted while the value of 0 indicates that it is not. I have learned that the most effective way to disperse the crowd that surrounds the office coffee machine is to engage into SQL Server debates. The bit data type has been one of the most reoccurring, as well as the most enjoyable, of these topics. It contains a practical side and a philosophical side. Practical Consideration This data type certainly has its place and is a valuable option for database design; but it is often used in situations where the answer is really not a pure true/false response. In addition, true/false values are not very informative or scalable. Let's use the previously noted [IsGasoline] column for illustration. While on the surface it appears to be a rather simple question when evaluating a car: "Does the car have a gasoline engine?" If the person entering data is entering a row for a Jeep Liberty, the response would be a 1 since it has a gasoline engine. If the person is entering data is entering a row for a Chevrolet Volt, the response would be a 0 since it is an electric engine. What happens when a person is entering a row for the gasoline/electric hybrid Toyota Prius? Would one person's conclusion be consistent with another person's conclusion? The argument could be made that the current intent for the database is to be used only for pure gasoline and pure electric engines; but this is where the scalability issue comes into play. With the use of a bit data type a database modification and data conversion would be required if the business decided to take on hybrid engines. Whereas, alternatively, if the int data type were used as a foreign key to a reference table containing the engine type options, the change to include the hybrid option would only require an entry into the reference table. Philosophical Consideration Since the bit data type is often used for true/false or yes/no data (also called Boolean) it presents a philosophical conundrum of what to do about the allowance of the NULL value. The inclusion of NULL in a true/false or yes/no response simply violates the logical principle of bivalence which states that "every proposition is either true or false". If NULL is not true, then it must be false. The mathematical laws of Boolean logic support this concept by stating that the only valid values of this scenario are 1 and 0. There is another way to look at this conundrum: NULL is also considered to be the absence of a response. In other words, it is the equivalent to "undecided". Anyone who watches the news can tell you that polls always include an "undecided" option. This could be considered a valid option in the world of yes/no/dunno. Through out all of these considerations I have discovered one absolute certainty: When you have found a person, or group of persons, who are willing to entertain a philosophical debate of the bit data type, you have found some true friends.

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• InnoDB Compression Improvements in MySQL 5.6

  - by Inaam Rana

  MySQL 5.6 comes with significant improvements for the compression support inside InnoDB. The enhancements that we'll talk about in this piece are also a good example of community contributions. The work on these was conceived, implemented and contributed by the engineers at Facebook. Before we plunge into the details let us familiarize ourselves with some of the key concepts surrounding InnoDB compression. In InnoDB compressed pages are fixed size. Supported sizes are 1, 2, 4, 8 and 16K. The compressed page size is specified at table creation time. InnoDB uses zlib for compression. InnoDB buffer pool will attempt to cache compressed pages like normal pages. However, whenever a page is actively used by a transaction, we'll always have the uncompressed version of the page as well i.e.: we can have a page in the buffer pool in compressed only form or in a state where we have both the compressed page and uncompressed version but we'll never have a page in uncompressed only form. On-disk we'll always only have the compressed page. When both compressed and uncompressed images are present in the buffer pool they are always kept in sync i.e.: changes are applied to both atomically. Recompression happens when changes are made to the compressed data. In order to minimize recompressions InnoDB maintains a modification log within a compressed page. This is the extra space available in the page after compression and it is used to log modifications to the compressed data thus avoiding recompressions. DELETE (and ROLLBACK of DELETE) and purge can be performed without recompressing the page. This is because the delete-mark bit and the system fields DB_TRX_ID and DB_ROLL_PTR are stored in uncompressed format on the compressed page. A record can be purged by shuffling entries in the compressed page directory. This can also be useful for updates of indexed columns, because UPDATE of a key is mapped to INSERT+DELETE+purge. A compression failure happens when we attempt to recompress a page and it does not fit in the fixed size. In such case, we first try to reorganize the page and attempt to recompress and if that fails as well then we split the page into two and recompress both pages. Now lets talk about the three major improvements that we made in MySQL 5.6.Logging of Compressed Page Images:InnoDB used to log entire compressed data on the page to the redo logs when recompression happens. This was an extra safety measure to guard against the rare case where an attempt is made to do recovery using a different zlib version from the one that was used before the crash. Because recovery is a page level operation in InnoDB we have to be sure that all recompress attempts must succeed without causing a btree page split. However, writing entire compressed data images to the redo log files not only makes the operation heavy duty but can also adversely affect flushing activity. This happens because redo space is used in a circular fashion and when we generate much more than normal redo we fill up the space much more quickly and in order to reuse the redo space we have to flush the corresponding dirty pages from the buffer pool.Starting with MySQL 5.6 a new global configuration parameter innodb_log_compressed_pages. The default value is true which is same as the current behavior. If you are sure that you are not going to attempt to recover from a crash using a different version of zlib then you should set this parameter to false. This is a dynamic parameter.Compression Level:You can now set the compression level that zlib should choose to compress the data. The global parameter is innodb_compression_level - the default value is 6 (the zlib default) and allowed values are 1 to 9. Again the parameter is dynamic i.e.: you can change it on the fly.Dynamic Padding to Reduce Compression Failures:Compression failures are expensive in terms of CPU. We go through the hoops of recompress, failure, reorganize, recompress, failure and finally page split. At the same time, how often we encounter compression failure depends largely on the compressibility of the data. In MySQL 5.6, courtesy of Facebook engineers, we have an adaptive algorithm based on per-index statistics that we gather about compression operations. The idea is that if a certain index/table is experiencing too many compression failures then we should try to pack the 16K uncompressed version of the page less densely i.e.: we let some space in the 16K page go unused in an attempt that the recompression won't end up in a failure. In other words, we dynamically keep adding 'pad' to the 16K page till we get compression failures within an agreeable range. It works the other way as well, that is we'll keep removing the pad if failure rate is fairly low. To tune the padding effort two configuration variables are exposed. innodb_compression_failure_threshold_pct: default 5, range 0 - 100,dynamic, implies the percentage of compress ops to fail before we start using to padding. Value 0 has a special meaning of disabling the padding. innodb_compression_pad_pct_max: default 50, range 0 - 75, dynamic, the  maximum percentage of uncompressed data page that can be reserved as pad.

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• Content Query Web Part and the Yes/No Field

  - by Bil Simser

  The Content Query Web Part (CQWP) is a pretty powerful beast. It allows you to do multiple site queries and aggregate the results. This is great for rolling up content and doing some summary type reporting. Here’s a trick to remember about Yes/No fields and using the CQWP. If you’re building a news style site and want to aggregate say all the announcements that people tag a certain way, up onto the home page this might be a solution. First we need to allow a way for users of all our sites to mark an announcement for inclusion on our Intranet Home Page. We’ll do this by just modifying the Announcement Content type and adding a Yes/No field to it. There are alternate ways of doing this like building a new Announcement type or stapling a feature to all sites to add our column but this is pretty low impact and only affects our current site collection so let’s go with it for now, okay? You can berate me in the comments about the proper way I should have done this part. Go to the Site Settings for the Site Collection and click on Site Content Types under the Galleries. This takes you to the gallery for this site and all subsites. Scroll down until you see the List Content Types and click on Announcements. Now we’re modifying the Announcement content type which affects all those announcement lists that are created by default if you’re building sites using the Team Site template (or creating a new Announcements list on any site for that matter). Click on Add from new site column under the Column list. This will allow us to create a new Yes/No field that users will see in Announcement items. This field will allow the user to flag the announcement for inclusion on the home page. Feel free to modify the fields as you see fit for your environment, this is just an example. Now that we’ve added the column to our Announcements Content type we can go into any site that has an announcement list, modify that announcement and flag it to be included on our home page. See the new Featured column? That was the result of modifying our Announcements Content Type on this site collection. Now we can move onto the dirty part, displaying it in a CQWP on the home page. And here is where the fun begins (and the head scratching should end). On our home page we want to drop a Content Query Web Part and aggregate any Announcement that’s been flagged as Featured by the users (we could also add the filter to handle Expires so we don’t show old content so go ahead and do that if you want). First add a CQWP to the page then modify the settings for the web part. In the first section, Query, we want the List Type to be set to Announcements and the Content type to be Announcement so set your options like this: Click Apply and you’ll see the results display all Announcements from any site in the site collection. I have five team sites created each with a unique announcement added to them. Now comes the filtering. We don’t want to include every announcement, only ones users flag using that Featured column we added. At first blush you might scroll down to the Additional Filters part of the Query options and set the Featured column to be equal to Yes: This seems correct doesn’t it? After all, the column is a Yes/No column and looking at an announcement in the site, it displays the field as Yes or No: However after applying the filter you get this result: (I have the announcements from Team Site 1 and Team Site 4 flagged as Featured) Huh? It’s BACKWARDS! Let’s confirm that. Go back in and change the Additional Filters section from Yes to No and hit Apply and you get this: Wait a minute? Shouldn’t I see Team Site 1 and 4 if the logic is backwards? Why am I seeing the same thing as before. What gives… For whatever reason, unknown to me, a Yes/No field (even though it displays as such) really uses 1 and 0 behind the scenes. Yeah, someone was stuck on using integer values for booleans when they wrote SharePoint (probably after a long night of white boarding ways to mess with developers heads) and came up with this. The solution is pretty simple but not very discoverable. Set the filter to include your flagged items like so: And it will filter the items marked as Featured correctly giving you this result: This kind of solution could also be extended and enhanced. Here are a few suggestions and ideas: Modify the ItemStyle.xsl file to add a new style for this aggregation which would include the first few paragraphs of the body (or perhaps add another field to the Content type called Excerpt or Summary and display that instead) Add an Image column to the Announcement Content type to include a Picture field and display it in the summary Add a Category choice field (Employee News, Current Events, Headlines, etc.) and add multiple CQWPs to the home page filtering each one on a different category I know some may find this topic old and dusty but I didn’t see a lot out there specifically on filtering the Yes/No fields and the whole 1/0 trick was a little wonky, so I figured a few pictures would help walk through overcoming yet another SharePoint weirdness. With a little work and some creative juices you can easily us the power of aggregation and the CQWP to build a news site from content on your team sites.

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• Serving and caching content from Amazon S3 with Tomcat

  - by Rob

  Hi all, We're looking to serve a range of content using Amazon S3 as a store for the content and Tomcat to host the web application. The content is divided into free and paid for content. We intend to authenticate the users when they access the web application running in Tomcat. Based around their authentication we are able to tell if the user has access to paid for content or simply free stuff. So I envision the flow of a request being something like this: Authenticated request to Tomcat If user is "paid" user, display links to premium content Direct requests for paid content back through Tomcat to prevent direct access to it by non-paying users. Tomcat makes request to S3 through a web cache to keep our costs down Content is returned to user. As we have to pay for each request to S3, I'd ideally like to cache content locally to the Tomcat instance after it has been requested for the first time to keep costs to a minimum and to speed things up. I would also like to be able to invalidate this cache if we publish fresh content to S3. So to confirm my proposal: Client Request - Tomcat - Web Cache - S3 To invalidate the cache, I was thinking of using something like PubSubHubbub with the cache waiting for updates to the feed for content that it should invalidate. I'd appreciate some general feedback on this approach as I've no real experience of caching and I'm sure I've made some invalid assumptions. I'd also appreciate any recommendations for caching technologies. Thanks.

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• Windows 7 task bar stuck in hiding, how to fix?

  - by Rainer Blome

  In Windows 7, I use the "Auto-hide the task bar" feature. Usually, it works fine: As soon as the pointer touches the screen bottom, the task bar pops up. However sometimes, it refuses to rise. Pressing the "Windows" key (or Ctrl-ESC) makes the start menu appear, forcing the task bar from hinding as well. Once I've done this, the task-bar auto-rises again. This is annoying, it interrupts flow. Has anyone else noticed this? How do I avoid this? Searching for "Windows 7 task bar auto-raise" shows that at least one other person experienced this problem: http://answers.microsoft.com/en-us/windows/forum/windows_7-desktop/how-can-i-fix-the-taskbars-auto-hide/8cdf6369-7354-4d29-9249-b7096ed0e28b?msgId=6dac3361-9d0f-4a9e-8642-b91a72826ba4 To answer the question posed by the "helpful" support engineer on the above page, of course I am running some apps when this happens, usually Explorer, Firefox, Eclipse, Cygwin/X, Xterm, Emacs, Notes, VPN client, Firewall. If my memory serves correctly, I have seen this behavior on earlier versions of Windows as well, XP at least. To reproduce this behavior, I tried switching between apps, and bringing apps to open other windows. I am unable to reproduce this behavior so far. So far, it appears to happen out of the blue, sometimes multiple times a day. Looks like a bug to me. The task bar should raise no matter what.

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• AWS VPC public web application connecting to database via VPN

  - by Chris

  What I am trying to do is set up a web application that is public facing but makes calls to a database that is on an internal network. I have been trying to set up an AWS VPC with a public subnet, private subnet, and hardware VPN access but I can't seem to get it to work. Can someone help me understand what the process flow here should be? My understanding is that I need a public subnet to handle the website requests and then a private subnet to connect to the VPN but what I do not understand is how to send requests down the chain and get the response. Basically what I am asking is how can I query the database via VPN from that public website? I've tried during rout forwarding but I can't successfully complete the process. Does anyone have any advice on something I can read on this subject or an FAQ on setting something like this up? Is it even possible? I'm out of my league here, this is not my area of expertise but I'm being asked to solve this problem. Any help would be appreciated. Thanks

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• Designing a software based load balancer

  - by Kishore pandey

  Hello to all Server fault users, I am new to this website but have constantly been using the mother website, stackover flow. Well to begin with, i would like to design a load balancer for the organization i am working for. As i am very new to this whole, idea about load balancing and networks. I am finding it very difficult to start my project. I did a lot of research on already existing load balancer and found some(HAPROXY,NGINX) that could solve my problems, but the point is, I am still in a dilemma if they could answer the following requirements of mine: The client and server in my architecture are distributed. The load balancer should take care of the firewall. LB server should balance the load among all servers present in WWW cloud. The LB server should have some sort of configuration file, with the help of which it is possible to configure the servers. Heart beat: With the help of which it would be possible to check if any server is down, if any server is down the request should be passed to some other server. Various load balancing algorithms of the incoming requests. Easy error handling. It should be fairly possible to prioritize the incoming requests. Is there any already available load balncer solution on the market that could satisfy these requirements? If not is there any base code available with the help of which i could develop my own load balncer. If not where should i start from scratch? I am practically new to everything. Any help from a load balancer expert is very much appreciated. Thanx a ton in advance. Cheers and regards. Kishore

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• Can Current Backflow from Powered Hub's Adapter & cause PC Damage?

  - by SuperUserMan

  Getting this short: Can current flow from a powered USB hub's power adapter (lying 10 Meter away) back to computer via usb port and cause damage to Computer components like mobo, etc? What should be my concerns? Using a 2 Amp 5V Power adapter to power a 10m Long Active Repeater USB extension cable with 4 port HUB & plugging into PC's Front port, causes PC Chassis fan to keep running (thought slower than regular speed) Front Chassis HDD & power LED to turn on (though bit dim) may be other things which i cant detect/see at chip level, in motherboard?? All this even after PC is shut down (bit scary) More detail (in case still want to read): To run 4 High power (needing 450 mAmps) Wifi Adapters, far away from PC, Bought Active Repeater USB Extension Cable with 4 Ports & power port at far end http://www.ebay.com/itm/33FT-USB-2-0-Male-to-Female-Extension-Cable-Hub-Splitter-Adapter-with-4-USB-Port-/390846115254 Then added a locally bought 2 Amp 240V AC to 5V DC Power Adapter and plugged into USB hub which is a part of & situated at far end of a 10 Meter Active Repeater usb extension cable. Even 4 Wifi Adapters run fine (appear to) using this setup, but running chassis fan, dimly lighted Power & HDD LED, even when PC is switched off is bit scary and surely mean 5V & some current is flowing all though that 10 meter extension cable into my USB port & powering stuff. Can this cause damage? and what should be my concerns. Of course I can't switch off the power adapter (lying 10 meters away from PC) every time I switch off my PC to prevent this.

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• ESXi 5 VM Putty session hangs, vSphere client timing out

  - by user192702

  First of all I believe this is a ESXi issue but let me know if you have seen this. It started about a year ago when I noticed occasionally when I putty via SSH to my VM guests, if I do anything that makes it to display a lot of things at once, the session will hang and I have to start a new one quite often only to find the same behaviour. What I meant by display a lot of things can be any of the following: 1) tail -f filename 2) Paste a long command 3) less filename If I type in one character at a time this won't happen. I tried searching online and it always point me to flow control settings and the various suggestions I've tried have never been able to resolve the issue. Since last week, I've noticed I'm not able to connect to my POP3 server from Outlook (it's timing out from Outlook's perspective). Today I tried to connect to the ESXi via vSphere client and it gives me a time out also. Exact behavior and error I saw is similar to the one posted at the following URL but the suggested technique also failed to resolve the issue. http://davidcocke.blogspot.hk/2012/02/unable-to-login-with-vsphere-client.html Has anyone experienced this before? Any suggestions on how to troubleshoot this?

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• Postfix relay all mail through SES except for one sending domain / address

  - by Kevin

  I'm thinking this is really really super simple, but I can't figure out what I need to do. I don't mess with Postfix much (Just let it run and do its thing) so I've got no idea where to even start with this. We have postfix currently configured to relay all mail out through SES using the code below. We need to modify this so that emails sent from one of our domains (domain.com) DO NOT go through SES. Everything else should continue to flow out through the SES connection. I'm assuming this is like a one line thing but my google skills are not helping me at all. relayhost = email-smtp.us-east-1.amazonaws.com:25 smtp_sasl_auth_enable = yes smtp_sasl_security_options = noanonymous smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd smtp_use_tls = yes smtp_tls_security_level = encrypt smtp_tls_note_starttls_offer = yes smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt smtp_destination_concurrency_limit = 450 Update I have created sender_transport file in /etc/postfix. In it is @domain.com smtp: I then ran this through postmap and placed sender_dependent_default_transport_maps = hash:/etc/postfix/sender_transport above the above block of code and restarted postfix, but still all email is going out through SES. Log after sending Oct 22 14:38:48 web postfix/smtp[19446]: 4B19D640002: to=<[email protected]>, relay=email-smtp.us-east-1.amazonaws.com[54.243.47.187]:25, delay=1.4, delays=0.01/0/0.92/0.44, dsn=2.0.0, status=sent (250 Ok 00000141e21b181f-ee6f7c4f-f0f5-4b0f-ba69-2db146a4f988-000000) Oct 22 14:38:48 web postfix/qmgr[19435]: 4B19D640002: removed I don't think this log is what you're looking for, but it's the only thing that is logged when mail goes out, and this is with me running /usr/sbin/postfix -v start manually and not with the init script.

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• Encrypting peer-to-peer application with iptables and stunnel

  - by Jonathan Oliver

  I'm running legacy applications in which I do not have access to the source code. These components talk to each other using plaintext on a particular port. I would like to be able to secure the communications between the two or more nodes using something like stunnel to facilitate peer-to-peer communication rather than using a more traditional (and centralized) VPN package like OpenVPN, etc. Ideally, the traffic flow would go like this: app@hostA:1234 tries to open a TCP connection to app@hostB:1234. iptables captures and redirects the traffic on port 1234 to stunnel running on hostA at port 5678. stunnel@hostA negotiates and establishes a connection with stunnel@hostB:4567. stunnel@hostB forwards any decrypted traffic to app@hostB:1234. In essence, I'm trying to set this up to where any outbound traffic (generated on the local machine) to port N forwards through stunnel to port N+1, and the receiving side receives on port N+1, decrypts, and forwards to the local application at port N. I'm not particularly concerned about losing the hostA origin IP address/machine identity when stunnel@hostB forwards to app@hostB because the communications payload contains identifying information. The other trick in this is that normally with stunnel you have a client/server architecture. But this application is much more P2P because nodes can come and go dynamically and hard-coding some kind of "connection = hostN:port" in the stunnel configuration won't work.

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• Can I use iptables on my Varnish server to forward HTTPS traffic to a specific server?

  - by Dylan Beattie

  We use Varnish as our front-end web cache and load balancer, so we have a Linux server in our development environment, running Varnish with some basic caching and load-balancing rules across a pair of Windows 2008 IIS web servers. We have a wildcard DNS rule that points *.development at this Varnish box, so we can browse http://www.mysite.com.development, http://www.othersite.com.development, etc. The problem is that since Varnish can't handle HTTPS traffic, we can't access https://www.mysite.com.development/ For dev/testing, we don't need any acceleration or load-balancing - all I need is to tell this box to act as a dumb proxy and forward any incoming requests on port 443 to a specific IIS server. I suspect iptables may offer a solution but it's been a long while since I wrote an iptables rule. Some initial hacking has got me as far as iptables -F iptables -A INPUT -p tcp -m tcp --sport 443 -j ACCEPT iptables -A OUTPUT -p tcp -m tcp --dport 443 -j ACCEPT iptables -t nat -A PREROUTING -p tcp --dport 443 -j DNAT --to 10.0.0.241:443 iptables -t nat -A POSTROUTING -p tcp -d 10.0.0.241 --dport 443 -j MASQUERADE iptables -A INPUT -j LOG --log-level 4 --log-prefix 'PreRouting ' iptables -A OUTPUT -j LOG --log-level 4 --log-prefix 'PostRouting ' iptables-save > /etc/iptables.rules (where 10.0.0.241 is the IIS box hosting the HTTPS website), but this doesn't appear to be working. To clarify - I realize there's security implications about HTTPS proxying/caching - all I'm looking for is completely transparent IP traffic forwarding. I don't need to decrypt, cache or inspect any of the packets; I just want anything on port 443 to flow through the Linux box to the IIS box behind it as though the Linux box wasn't even there. Any help gratefully received... EDIT: Included full iptables config script.

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• Booting Ubuntu as VM with KVM on Ubuntu 12.04

  - by CrazycodeMonkey

  I am trying to boot my very first VM using KVM. I have Ubuntu 12.04 installed, i made sure the BIOS had the right virtualization flag enabled for intel processor by running kvm-ok. I have researched this on google and all the instructions that i have found so far are outdated. for e.g. most instructions talk about booting a virtual machine with the following commands qemu-img create -f qcow2 foo.img 100G --- create a virtual disk for your VM kvm --name foo -m 1024 -hda foo.img -cdrom whatever.iso -boot d -- This runs kvm. This command line is incomplete. First you need to be root to run this. Second- it is missing option for the video device. When you run this command you get the following error "Could not initialize SDL(No available video device) - exiting" Googled this error and looked it up on stackover flow http://stackoverflow.com/questions/4841908/sdl-init-failure-reason-is-no-available-video-device The answer provided here does not work on Ubuntu 12.04 Googled this problem further and found out that i need to specify a video device so I finally ran the following command sudo kvm --name mymachine -m 8096 -hda myimage.img --cdrom ubuntu.iso -boot d -vga cirruss -k en-us -vmc :0 This was after I had created the myimage.img image on the drive. Now this command does not give me an error but it just hangs. Does anyone have clear instructions on how to run a VM using KVM on Ubuntu?

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• Windows 7 hangs with 100% disk activity but only when online

  - by jeremy

  I have the same problem as seemingly many other people here, and I think we might all be experiencing the same issue: a compatibility issue in Windows 7 between hard drive and network controller or drivers. I've tried firmware updates of my entire board, wiping my drive and reinstalling from scratch. And yet the problem persists, which suggests it is an operating system error, as the hard drive checks out 100% physically. Additionally, the only time it does not occur is when in safe mode WITHOUT networking. With networking, there are spikes in disc access every so often and a huge flow of processes accessing the disc simultaneously that literally "stick" the disc, and physically jolting my computer unsticks it. Again, this has been tested for hours in a professional service environment, and without network access on, things are fine. As soon as there's network access available, the disc access occasionally cranks up to 100% and sticks everything. I'm using Microsoft Security Essentials, but this also happened under Norton, then McAfee. Again, this happened again after a complete wipe, so the likelihood of malware causing it seems low. I don't visit unsecure sites anyway, as far as I know. This, to me, narrows it down to a Windows 7 process that is somehow repeatedly corrupted, perhaps a corrupt .dll or driver, causing a conflict at the operating system level and temporary hard drive failure. I would encourage anyone who knows more about this stuff (which is probably most people!) to take a shot at this one, and I would encourage anyone else with a sticking hard drive in windows 7 64-bit to check on whether it occurs during safe mode without networking.

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• The sign of a true manager is delegation (C# style)

  - by MarkPearl

  Today I thought I would write a bit about delegates in C#. Up till recently I have managed to side step any real understanding of what delegates do and why they are useful – I mean, I know roughly what they do and have used them a lot, but I have never really got down dirty with them and mucked about. Recently however with my renewed interest in Silverlight delegates came up again as a possible solution to a particular problem, and suddenly I found myself opening a bland little console application to just see exactly how far I could take delegates with my limited knowledge. So, let’s first look at the MSDN definition of delegates… A delegate declaration defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure. Well, don’t you love MSDN for such a useful definition. I must give it credit though… later on it really explains it a bit better by saying “A delegate lets you pass a function as a parameter. The type safety of delegates requires the function you pass as a delegate to have the same signature as the delegate declaration.” A little more reading up on delegates mentions that delegates are similar to interfaces in that they enable the separation of specification and implementation. A delegate declares a single method, while an interface declares a group of methods. So enough reading - lets look at some code and see a basic example of a delegate… Let’s assume we have a console application with a simple delegate declared called AdjustValue like below… class Program { private delegate int AdjustValue(int val); static void Main(string[] args) { } } In a sense, all we have said is that we will be creating one or more methods that follow the same pattern as AdjustValue – i.e. they will take one input value of type int and return an integer. We could then expand our code to have various methods that match the structure of our delegate AdjustValue (remember the structure is int xxx (int xxx)) class Program { private delegate int AdjustValue(int val); private static int Dbl(int val) { return val * 2; } private static int AlwaysOne(int val) { return 1; } static void Main(string[] args) { } }  Above I have expanded my project to have two methods, one called Dbl and the other AlwaysOne. Dbl always returns double the input val and AlwaysOne always returns 1. I could now declare a variable and assign it to be one of those functions, like the following… class Program { private delegate int AdjustValue(int val); private static int Dbl(int val) { return val * 2; } private static int AlwaysOne(int val) { return 1; } static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; Console.WriteLine(myDelegate(1).ToString()); Console.ReadLine(); } } In this instance I have declared an instance of the AdjustValue delegate called myDelegate; I have then told myDelegate to point to the method Dbl, and then called myDelegate(1). What would the result be? Yes, in this instance it would be exactly the same as me calling the following code… static void Main(string[] args) { Console.WriteLine(Dbl(1).ToString()); Console.ReadLine(); }   So why all the extra work for delegates when we could just do what we did above and call the method directly? Well… that separation of specification to implementation comes to mind. So, this all seems pretty simple. Let’s take a slightly more complicated variation to the console application. Assume that my project is the same as the one previously except that my main method is adjusted as follows… static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; myDelegate = AlwaysOne; Console.WriteLine(myDelegate(1).ToString()); Console.ReadLine(); } What would happen in this scenario? Quite simply “1” would be written to the console, the reason being that myDelegate was last pointing to the AlwaysOne method before it was called. Make sense? In a way, the myDelegate is a variable method that can be swapped and changed when needed. Let’s make the code a little more confusing by using a delegate in the declaration of another delegate as shown below… class Program { private delegate int AdjustValue(InputValue val); private delegate int InputValue(); private static int Dbl(InputValue val) { return val()*2; } private static int GetInputVal() { Console.WriteLine("Enter a whole number : "); return Convert.ToInt32(Console.ReadLine()); } static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; Console.WriteLine(myDelegate(GetInputVal).ToString()); Console.ReadLine(); } }   Now it gets really interesting because it looks like we have passed a method into a function in the main method by declaring… Console.WriteLine(myDelegate(GetInputVal).ToString()); So, what it the output? Well, try take a guess on what will happen – then copy the code and see if you got it right. Well that brings me to the end of this short explanation of Delegates. Hopefully it made sense!

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• Linux boot - stop the kernel switching to a new framebuffer mode clearing output

  - by Avio

  I'm working on an embedded system (based onUbuntu 12.04 LTS) and I'm customizing its kernel. I'm having some problem with upstart, mountall and plymouth. Nothing unsolvable I suppose, but the real problem is that I can't diagnose properly what's going on because the kernel (or maybe plymouth) changes the video mode in the middle of the boot process. This completely wipes entire lines of log and prevents any debugging of kernel misconfigurations. My Grub2 config seems to be ok with: GRUB_CMDLINE_LINUX="" GRUB_CMDLINE_LINUX_DEFAULT="acpi=force noplymouth" GRUB_GFXMODE=1024x768x32 GRUB_GFXPAYLOAD_LINUX=keep Here is some relevant output of lspci: 00:00.0 Host bridge: Intel Corporation Mobile 945GSE Express Memory Controller Hub (rev 03) 00:02.0 VGA compatible controller: Intel Corporation Mobile 945GSE Express Integrated Graphics Controller (rev 03) 00:02.1 Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03) And here is the relevant portion of my kernel configuration: CONFIG_AGP=y CONFIG_AGP_INTEL=y CONFIG_VGA_ARB=y CONFIG_VGA_ARB_MAX_GPUS=16 CONFIG_DRM=y CONFIG_DRM_KMS_HELPER=y CONFIG_DRM_I915=y CONFIG_DRM_I915_KMS=y CONFIG_VIDEO_OUTPUT_CONTROL=y CONFIG_FB=y CONFIG_FB_BOOT_VESA_SUPPORT=y CONFIG_FB_CFB_FILLRECT=y CONFIG_FB_CFB_COPYAREA=y CONFIG_FB_CFB_IMAGEBLIT=y CONFIG_FB_MODE_HELPERS=y CONFIG_FB_VESA=y CONFIG_BACKLIGHT_LCD_SUPPORT=y CONFIG_BACKLIGHT_CLASS_DEVICE=y CONFIG_VGA_CONSOLE=y CONFIG_VGACON_SOFT_SCROLLBACK=y CONFIG_VGACON_SOFT_SCROLLBACK_SIZE=640 CONFIG_DUMMY_CONSOLE=y CONFIG_FRAMEBUFFER_CONSOLE=y CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY=y CONFIG_FONT_8x8=y CONFIG_FONT_8x16=y CONFIG_LOGO=y CONFIG_LOGO_LINUX_MONO=y CONFIG_LOGO_LINUX_VGA16=y CONFIG_LOGO_LINUX_CLUT224=y Every other custom/stock kernel boot fine with that Grub2 config. What I would like to have is a single flow of messages on a single console (retaining one screen resolution) from the bootup logo till the login prompt. Does anybody know what I have to tweak to achieve this?

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• How could I embed formatted XML source in WORD documents?

  - by eckes

  I'm writing a documentation with WORD that contains XML source code (whole files) as examples. The way I'm embedding the currently XML is quite cumbersome and doesn't seem to me as really maintainable: I'm finishing the editing of the document in WORD and create a PDF from it using Acrobat next, I open my XML files (2x input files, 2x generated output files) with IE and print them with the PDF printer supplied by Acrobat now, I open up Acrobat Pro and attach the four XML-PDF files to my original document The problem with that work flow for me is that it involves too much manual labor in order to get the documentation done. What I've tried up to now is not really satisfying for me: converting each XML to PDF and appending them like described above opening the XML files with SCiTE, copy as RTF and paste into Word playing around with the LaTeX packages minted, pygments and listings (I could write the docs with LaTeX too) but found some unsolvable problems in each of these packages I'm searching for a way that produces my documentation more automatic. For example embedding the XML files including formatting of IE (which I find quite readable). The files should be included by reference so that I don't have to paste the XML sources manually every time the XML changes.

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• Redmine does not return the web page

  - by m0skit0

  I migrated a Redmine installation from an Ubuntu machine to a Debian one (both 32-bits), and now for some reason, for some users it doesn't return the page but only a 200 OK message. Here is the flow (from Wireshark): GET /issues/142 HTTP/1.1 Host: debian:3000 User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:17.0) Gecko/20100101 Firefox/17.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate Connection: keep-alive Cookie: _redmine_session=BAh7DCIQX2NzcmZfdG9rZW4iMStIM1RBNTlNelZVUXlUazgrR1pUNGUvNGdEbytUZzRyMVFSUnBvNGhlSDg9Ihd0aW1lbG9nX2luZGV4X3NvcnQiEnNwZW50X29uOmRlc2MiD3Nlc3Npb25faWQiJThiMDk0MzVhOTEzYTI0MzVjOGEzYTRmNDU0NzcwMTAwIgx1c2VyX2lkaQoiFmlzc3Vlc19pbmRleF9zb3J0IgxpZDpkZXNjIg1wZXJfcGFnZWlpIgpxdWVyeXsHOg9wcm9qZWN0X2lkaQc6B2lkaQo%3D--8588c221c0642a12f396239455fb702aec14c9c9; my_wiki_session=f70ae11e1c533c86f0e039d63cf3f69c; my_wikiUserID=1; my_wikiUserName=Yasin Cache-Control: max-age=0 HTTP/1.1 200 OK Connection: Keep-Alive Date: Wed, 12 Dec 2012 16:30:16 GMT Server: WEBrick/1.3.1 (Ruby/1.8.7/2010-08-16) Content-Length: 0 As you can see, I get nothing from the server. This is mostly random because this blank page happens sometimes for some users, and for other users it almost never returns the page... I'm absolutely lost here. Any idea about what can be the cause? Thanks in advance!

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• USB-to-Serial showing gibberish at 115200 Baud

  - by Mose

  I've got a serious problem which drives me crazy because I tried everything I could think of. First of all, I made a video: http://youtu.be/boghkuq7L_s but please read the following text for more information, not only view the video! When using a USB-to-Serial interface everything works as long as I don't go beyond 57600 Baud. At higher rates I only get giberish like this: év.­b0JNLYÆÿ¿iëd0U²(kßÞb! ú]/xscB!ï¯!BoXûÿ1ïâÖCÿ6ÌAnè*íÌC)º¿BíÞØ.C.@ÆÃwHJÂs "YE:ñ.èFðÌCÊ÷ÞÄ !x H w6@BtbHJ ̪ Ì6ì H¾a¿bH.">îvy®;f<ßBÌ p­L¨fæH­E ­þ¼MBÞI What makes the problem so strange is, I exchanged every component and the problem still presists. I tried differtent OSes (Ubuntu, WinXP, Win7, OSX 10.7) with 32 and 64 Bit. I tried USB-to-Serial interface from FTDI and Prolific. I tried reading the output from my Raspberry PI and from an Asterisk Appliance. I changed the cables and the wiring. Nothing helped. In the video I made a example with a old Notebook with native COM and put the USB-to-Serial to the same connection as "sniffer" (only Rx and GND connected) to make sure the output and everything is ok as one can see on the native port. The voltage is ok. Settings for both are 115200 Baud, 8 Bit with 1 Stop and no flow control. Native is ok. USB is messed up. I used the newest drivers and double checked all connections. I have no idea what is wrong here. As I couldn't find anyone describing problems like this I question my long experiance in computer science and think I'm doing some completly wrong... Please help :-/

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• Server-side SSH jump hosts

  - by Dan Sosedoff

  Trying to figure out server side SSH jump hosts logic. Current network schema: [Client] <--> [Server A: hostname: a.com] <--> [Server B] [Client] <--> [Server A: hostname: b.com] <--> [Server C] Server A responds to both DNS records. Possible flow: Client opens a ssh connection with ssh [email protected]. Server A accepts it and should automatically jump user onto Server B with ssh user2@server_b.com. Client opens a ssh connection with ssh [email protected]. Server A accepts it and should automatically just user onto Server C with ssh user2@server_c.com. In other words, client should be able to connect to the target without performing any local configuration, assuming that we have a stock ssh config. The problem with ssh jumps is that user has to define hosts in local ~/.ssh/config file, which is not acceptable in my case. It needs to be a default sshd behavior. Im aware that you can define a custom command ~/.ssh/authorized_keys on server, but i dont think there is a way to properly detect source hostname where user tries to connect. It is possible at all ?

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• Using XA Transactions in Coherence-based Applications

  - by jpurdy

  While the costs of XA transactions are well known (e.g. increased data contention, higher latency, significant disk I/O for logging, availability challenges, etc.), in many cases they are the most attractive option for coordinating logical transactions across multiple resources. There are a few common approaches when integrating Coherence into applications via the use of an application server's transaction manager: Use of Coherence as a read-only cache, applying transactions to the underlying database (or any system of record) instead of the cache. Use of TransactionMap interface via the included resource adapter. Use of the new ACID transaction framework, introduced in Coherence 3.6.   Each of these may have significant drawbacks for certain workloads. Using Coherence as a read-only cache is the simplest option. In this approach, the application is responsible for managing both the database and the cache (either within the business logic or via application server hooks). This approach also tends to provide limited benefit for many workloads, particularly those workloads that either have queries (given the complexity of maintaining a fully cached data set in Coherence) or are not read-heavy (where the cost of managing the cache may outweigh the benefits of reading from it). All updates are made synchronously to the database, leaving it as both a source of latency as well as a potential bottleneck. This approach also prevents addressing "hot data" problems (when certain objects are updated by many concurrent transactions) since most database servers offer no facilities for explicitly controlling concurrent updates. Finally, this option tends to be a better fit for key-based access (rather than filter-based access such as queries) since this makes it easier to aggressively invalidate cache entries without worrying about when they will be reloaded. The advantage of this approach is that it allows strong data consistency as long as optimistic concurrency control is used to ensure that database updates are applied correctly regardless of whether the cache contains stale (or even dirty) data. Another benefit of this approach is that it avoids the limitations of Coherence's write-through caching implementation. TransactionMap is generally used when Coherence acts as system of record. TransactionMap is not generally compatible with write-through caching, so it will usually be either used to manage a standalone cache or when the cache is backed by a database via write-behind caching. TransactionMap has some restrictions that may limit its utility, the most significant being: The lock-based concurrency model is relatively inefficient and may introduce significant latency and contention. As an example, in a typical configuration, a transaction that updates 20 cache entries will require roughly 40ms just for lock management (assuming all locks are granted immediately, and excluding validation and writing which will require a similar amount of time). This may be partially mitigated by denormalizing (e.g. combining a parent object and its set of child objects into a single cache entry), at the cost of increasing false contention (e.g. transactions will conflict even when updating different child objects). If the client (application server JVM) fails during the commit phase, locks will be released immediately, and the transaction may be partially committed. In practice, this is usually not as bad as it may sound since the commit phase is usually very short (all locks having been previously acquired). Note that this vulnerability does not exist when a single NamedCache is used and all updates are confined to a single partition (generally implying the use of partition affinity). The unconventional TransactionMap API is cumbersome but manageable. Only a few methods are transactional, primarily get(), put() and remove(). The ACID transactions framework (accessed via the Connection class) provides atomicity guarantees by implementing the NamedCache interface, maintaining its own cache data and transaction logs inside a set of private partitioned caches. This feature may be used as either a local transactional resource or as logging XA resource. However, a lack of database integration precludes the use of this functionality for most applications. A side effect of this is that this feature has not seen significant adoption, meaning that any use of this is subject to the usual headaches associated with being an early adopter (greater chance of bugs and greater risk of hitting an unoptimized code path). As a result, for the moment, we generally recommend against using this feature. In summary, it is possible to use Coherence in XA-oriented applications, and several customers are doing this successfully, but it is not a core usage model for the product, so care should be taken before committing to this path. For most applications, the most robust solution is normally to use Coherence as a read-only cache of the underlying data resources, even if this prevents taking advantage of certain product features.

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• mail server checklist..

  - by Jeff

  currently we ran into some issues with our mail server setup. im preparing a list of actions that we should enforce and use in order to maintain a proper email solution within our company. we have around 80 exchange users, and send mass emails out almost on a monthly bases to 20,000 + customers each time.. the checklist i currently have: 1) mcafee mxlogic 'cloud' anti-spam functionality for incoming message. 2) antivirus on each computer in company 3) antivirus on exchange and DNS servers 4) setup SPF record 5) setup DKIM 6) setup domainkey 7) setup senderID 8) submit spf to microsoft, yahoo, etc. for 'whitelist' purposes. 9) configure size limits for messages in exchange to safe numbers 10) i have 2 outside IPs for my email server, incase one gets blacklisted, switch to the backup. 11) my internet site rests on a different ip than the mail server 12) all mass emails for company sent through 3rd party company (listtrak.com) 13) setup domain alias, media, enews, and bounce for the 3rd party mass mail software. 14) verify the setup using [email protected] 15) configure group policy and our opendns.org account to prevent unwanted actions and website viewing mass emails: 1) schedule them to send different amounts at different times (1,000 at 10am, 1,000 at 4pm, 1,000 10am next day).. 2) setup user prefences, decide what they want to receive ect. ( there interests) 3) send a more steady flow of email, maybe 100 a week with top new products instead of 20,000k every other month.. if anyone has suggestions or additions/subtractions to this checklist they are greatly appreciated. thank you

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• Need a helpful/managed VPS to help transition from shared hosting

  - by Xeoncross

  I am looking for a VPS that can help me transition out of a shared hosting environment. My main OS is Ubuntu, although I am still new to the linux world. I spend most of my day programming PHP applications using a git over SSH workflow. I want PHP, SSH, git, MySQL/PostgreSQL and Apache to work well. Someday after I figure out server management I'll move on to http://nginx.org/ or something. I don't really understand 1) linux firewalls, 2) mail servers, or 3) proper daily package/lib update flow. I need a host that can help with these so I don't get hit with a security hole. (I monitor apache access logs so I think I can take it from there.) I want to know if there is a sub $50/m VPS that can help me learn (or do for me) these three main things I need to run a server. I can't leave my shared hosts (plural shows my need!) until I am sure my sites will be safe despite my incompetence. To clarify again, I need the most helpful, supportive, walk-me-through, check-up-on-me, be-there-when-I-need you VPS I can get. Learning isn't a problem when there is someone to turn too. ;)

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• How do I connect to and factory reset a Catalyst 3560 Switch?

  - by Josh

  My company just bought another company. In their server room they had some older hardware, which I would like to repurpose. One of these is a Cisco Switch: C3560G-48TS-S. I found some instructions about this switch here but this is not a guide for a beginner. I have no idea how to connect to this thing to begin running the commands. It says Configure the PC terminal emulation software for 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control. But I can't find anything on how to do this (assuming with telnet?) or even what program to use. I also don't know how to find the IP address of the device to connect to it. My research also says once I get in there, I need to run clear config all Is this the right command? Also, what if I can't get the username and password for these devices? Is there some way to factory reset (my only experience is with devices that have a hardware reset button) EDIT: I should note that when I push the button on the front the three lights blink, which according to the documentation indicated the switch is configured and "not available for express setup"

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