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  • Is embedded programming closer to electrical engineering or software development?

    - by Jeremy Heiler
    I am being approached with a job for writing embedded C on micro controllers. At first I would have thought that embedding programming is to low on the software stack for me, but maybe I am thinking about it wrong. Normally I would have shrugged off an opportunity to write embedded code, as I don't consider myself an electrical engineer. Is this a bad assumption? Am I able to write interesting and useful software for embedded systems, or will I kick myself for dropping too low on the software stack? I went to school for computer science and really enjoyed writing a compiler, managing concurrent algorithms, designing data structures, and developing frameworks. However, I am currently employed as a Flex developer, which doesn't scream the interesting things I just described. (I currently deal with issues like: "this check box needs to be 4 pixels to the left" and "this date is formatted wrong".) I appreciate everyone's input. I know I have to make the decision for myself, I just would like some clarification on what it means to be a embedded programmer, and if it fits what I find to be interesting.

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  • English major new to programming. What language should I learn first? [closed]

    - by PJKaka
    After working extensively an internet startup in a marketing positions, I've decided to wade into the entrepreneurship pool with a startup of my own. The only problem: I don't have any particular technical skills to speak of. Although I can find a technical co-founder, I'd rather not be the stereotypical 'business guy' drumming his fingers on the desk and asking 'how much longer?' as my technical co-founder codes away. I would like to understand code and what's happening in the backend, even if I don't end up being anything more than a 'passable' programmer. With this in mind, which language should I try to learn first? For the record, I'm quite proficient with HTML, CSS, and a bit of JavaScript. I have some familiarity with PHP because I've toyed around with WordPress a lot, but my knowledge is limited at best. My math skills are quite strong. I took some advanced calculus courses in college since I've always enjoyed the subject. While my goals are to learn web development, I wouldn't mind learning some hardcore object oriented programming skills in C or Java as well.

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  • How to search the web for programming related solutions?

    - by Bob
    I have the impression that Google has become unusable when searching for programming related questions. Example: I'm Googling for XML-RPC Redstone Cookie I'm expecting results where all three terms are contained. I don't care for results where one term misses. I guess until some months ago Google just worked this way, i.e. all terms were included. Somehow this feature is gone now (Google apparently thinks it is more intelligent than the user and knows what the user is searching for). So I helped myself putting a + in front of every word. This is, however, a bit cumbersome. And for the last weeks, it even doesn't work anymore in all cases, Google ignores the +. So how do you search for progamming related problems? Do you still use Google? If yes, which techniques do you use to get the right results? Or do you use another search engine? Which one?

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  • How come there is still so much programming work?

    - by jd_505
    First I'd like to say that I am not pretty sure that this question will meet the guidelines. I think it can goes under the "Freelancing and business concerns" bullet, but I am not sure. Anyway, I will give it a shot. I wonder how the programming jobs hasn't yet "dried" because of the software evolution, for example, I am a developer myself, which means that I do care about software (I mean I am not of the type of guys that needs a computer mainly to just browse the Internet), and still I wouldn't mind if I never receive any more updates on my Ubuntu machine. I find that it provides everything I need, and while the updates provide various bug fixes/improvements, I wouldn't mind using it with it's current state for the rest of my life, for 2 years of Ubuntu usage I have never bumped at a serious bug/problem. Another example is Windows, almost half of it's users still use XP, which is practically ancient, yet they find it satisfying all their needs (and I agreee with them). I could go with many more examples, but by now you are understanding my point and my question. While new "trends" appears all of the time (like a new mobile OS) which runs on new platforms and requires some fresh development work, still the majority of the software effort goes in to what I consider as "completed projects", or at least a state of a project which is enough to be considered as completed. Do you have an explanation ? I can't think of the right tags for this question, please edit it the way you find it to be most appropriate. Thanks.

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  • How complex/straightforward should my programming challenge response in an interview be? [closed]

    - by atraudes
    I've had a couple of interviews for programmer positions in the past couple of weeks, and just about all of them have presented me with programming challenges. Write a program with XX language that can solve XX puzzle or problem, etc. I've had no problem answering the questions. What I'm unsure about is what the depth and breadth my response should be. What would an ideal response look like? How much oomph and time should I spend on elements of the code that aren't crucial to it running (Comments, Javadoc, error handling, etc.)? What if I have 1 hour/6 hours/a whole weekend to spend on it? What are the most important aspects of my response to the interviewer? What's worked for you in the past or what worked on you as an interviewer? I'm definitely one of those folks that can go all out on a project and make it truly shine, but I don't want to give them the impression that I'm going to waste their time and money on stuff they may not want or care about. I have a sneaking feeling there is no "wrong" way to respond to the challenge; each response has a redeeming quality about it, and the goals of the interview are subjective. Regardless, I would love your thoughts and input on this.

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  • How come there is still so much programming work?

    - by jd_505
    I wonder why programming jobs haven't yet "dried up" because of the software evolution, for example, I am a developer myself, which means that I do care about software (I mean I am not of the type of guys that needs a computer mainly to just browse the Internet), and still I wouldn't mind if I never receive any more updates on my Ubuntu machine. I find that it provides everything I need, and while the updates provide various bug fixes/improvements, I wouldn't mind using it with its current state for the rest of my life, for 2 years of Ubuntu usage I have never bumped at a serious bug/problem. Another example is Windows, almost half of it's users still use XP, which is practically ancient, yet they find it satisfying all their needs (and I agree with them). I could go with many more examples, but by now you are understanding my point and my question. While new "trends" appears all of the time (like a new mobile OS) which runs on new platforms and requires some fresh development work, still the majority of the software effort goes in to what I consider as "completed projects", or at least a state of a project which is enough to be considered as completed. Do you have an explanation? I can't think of the right tags for this question; please edit it the way you find it to be most appropriate.

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  • initrd problem and Kernel panics after openSUSE 11.2 upgrade.

    - by unixbhaskar
    Once I have done the upgrade form openSUSE11.1 to openSUSE11.2 by doing this: zypper dup Now I tried to boot the system and it failed sync with VFS and kernel panic, so clearly a initrd problem . if I'm not mistaken. Now a bit of explanation about the problem: while upgrading it shows me the error updating initramfs( I forgot the exact error or might be warning).Oh yeah it shows some grub warning too. I have had been doing that from a chroot environment.. with all the required file mounted in proper place in the chroot environment. Now .after bit googling and painfully looking the susegeek.com forum and opensuse.org forum I have decided to recreate the initrd ...but the fellow called "mkinitrd" is real real crap as I hev been pointed out by few forum members. I tried to make an initrd image by myself, failed to do so .as it shows error that device not found( if I boot into suse live cd and mount the partition ) then I tried from the chrooted env and it says "there is no space left on the device" A bit bemused :( yeah most of you pointed it right may lack of knowledge of mine. Kindly suggest me and show me steps to do it correctly and get opensuse11.2 up and running. TIA

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  • How do I get Tomcat 7 to start up faster in Linux CentOS kernel version 2.6.18?

    - by user1786833
    I am experiencing a problem with slow start up times for Tomcat 7. I have done some testing by tweaking configuration parameters both on Linux CentOS kernel version 2.6.18 and on Windows 7 using this link as my primary guide: http://wiki.apache.org/tomcat/HowTo/FasterStartUp and managed only a modest improvement. The improvements seemed to result when I added metadata-complete="true" attribute to the element of my WEB-INF/web.xml file and when I added the names of almost all the jars we use for our application to the tomcat.util.scan.DefaultJarScanner.jarsToSkip property in conf/catalina.properties file. I've also used this JAVA_OPTS in the setenv.sh file: JAVA_OPTS="$JAVA_OPTS -server -Xms1536m -Xmx1536m -XX:MaxPermSize=256m -XX:NewRatio=2 -XX:+UseParallelGC -XX:ParallelGCThreads=2 -Dsun.rmi.dgc.client.gcInterval=1800000 -Dsun.rmi.dgc.server.gcInterval=1800000 -Dorg.apache.jasper.runtime.BodyContentImpl.LIMIT_BUFFER=true " but actually saw my start up times increase slightly. Our QA and production environments are on Linux CentOS so I'm hoping to get more information on improving Tomcat 7 start up times in that environment. My primary role is java developer and I don't have much system administration experience so I appreciate any input. Thank you for your time and suggestions.

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  • Wireless will not connect

    - by azz0r
    Hello, I have installed Ubuntu 10.10 on the same machine as my windows setup. However, it will not connect to my wireless network. It can see its there, it can attempt to connect, yet it will never connect. It will keep bringing up the password prompt everyso often. I have tried turning my security to WEP, I ended up turning it back to WPA2. It is set to AES (noted a few threads on google about that). Can you assist? I would love to dive into Ubuntu, but without the internet its pointless. --- lshw -C network --- *-network description: Ethernet interface product: RTL8111/8168B PCI Express Gigabit Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:02:00.0 logical name: eth0 version: 02 serial: 00:1d:92:ea:cc:62 capacity: 1GB/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix vpd bus_master cap_list rom ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8168 driverversion=8.020.00-NAPI duplex=half latency=0 link=no multicast=yes port=twisted pair resources: irq:29 ioport:e800(size=256) memory:feaff000-feafffff memory:f8ff0000-f8ffffff(prefetchable) memory:feac0000-feadffff(prefetchable) *-network description: Wireless interface physical id: 1 logical name: wlan0 serial: 00:15:af:72:a4:38 capabilities: ethernet physical wireless configuration: broadcast=yes multicast=yes wireless=IEEE 802.11bgn --- iwconfig ---- lo no wireless extensions. eth0 no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"Wuggawoo" Mode:Managed Frequency:2.437 GHz Access Point: Not-Associated Tx-Power=9 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:on --- cat /etc/network/interfaces ---- auto lo iface lo inet loopback logs deamon.log --- Jan 19 04:17:09 ubuntu wpa_supplicant[1289]: Authentication with 94:44:52:0d:22:0d timed out. Jan 19 04:17:09 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: associating -> disconnected Jan 19 04:17:09 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: disconnected -> scanning Jan 19 04:17:11 ubuntu wpa_supplicant[1289]: WPS-AP-AVAILABLE Jan 19 04:17:11 ubuntu wpa_supplicant[1289]: Trying to associate with 94:44:52:0d:22:0d (SSID='Wuggawoo' freq=2437 MHz) Jan 19 04:17:11 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: scanning -> associating Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0/wireless): association took too long. Jan 19 04:17:12 ubuntu NetworkManager: <info> (wlan0): device state change: 5 -> 6 (reason 0) Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0/wireless): asking for new secrets Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0) Stage 1 of 5 (Device Prepare) scheduled... Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0) Stage 1 of 5 (Device Prepare) started... Jan 19 04:17:12 ubuntu NetworkManager: <info> (wlan0): device state change: 6 -> 4 (reason 0) Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0) Stage 2 of 5 (Device Configure) scheduled... Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0) Stage 1 of 5 (Device Prepare) complete. Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0) Stage 2 of 5 (Device Configure) starting... Jan 19 04:17:12 ubuntu NetworkManager: <info> (wlan0): device state change: 4 -> 5 (reason 0) Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0/wireless): connection 'Wuggawoo' has security, and secrets exist. No new secrets needed. Jan 19 04:17:12 ubuntu NetworkManager: <info> Config: added 'ssid' value 'Wuggawoo' Jan 19 04:17:12 ubuntu NetworkManager: <info> Config: added 'scan_ssid' value '1' Jan 19 04:17:12 ubuntu NetworkManager: <info> Config: added 'key_mgmt' value 'WPA-PSK' Jan 19 04:17:12 ubuntu NetworkManager: <info> Config: added 'psk' value '<omitted>' Jan 19 04:17:12 ubuntu NetworkManager: nm_setting_802_1x_get_pkcs11_engine_path: assertion `NM_IS_SETTING_802_1X (setting)' failed Jan 19 04:17:12 ubuntu NetworkManager: nm_setting_802_1x_get_pkcs11_module_path: assertion `NM_IS_SETTING_802_1X (setting)' failed Jan 19 04:17:12 ubuntu NetworkManager: <info> Activation (wlan0) Stage 2 of 5 (Device Configure) complete. Jan 19 04:17:12 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: associating -> disconnected Jan 19 04:17:12 ubuntu NetworkManager: <info> Config: set interface ap_scan to 1 Jan 19 04:17:12 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: disconnected -> scanning Jan 19 04:17:13 ubuntu wpa_supplicant[1289]: WPS-AP-AVAILABLE Jan 19 04:17:13 ubuntu wpa_supplicant[1289]: Trying to associate with 94:44:52:0d:22:0d (SSID='Wuggawoo' freq=2437 MHz) Jan 19 04:17:13 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: scanning -> associating Jan 19 04:17:23 ubuntu wpa_supplicant[1289]: Authentication with 94:44:52:0d:22:0d timed out. Jan 19 04:17:23 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: associating -> disconnected Jan 19 04:17:23 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: disconnected -> scanning Jan 19 04:17:24 ubuntu AptDaemon: INFO: Initializing daemon Jan 19 04:17:25 ubuntu wpa_supplicant[1289]: WPS-AP-AVAILABLE Jan 19 04:17:25 ubuntu wpa_supplicant[1289]: Trying to associate with 94:44:52:0d:22:0d (SSID='Wuggawoo' freq=2437 MHz) Jan 19 04:17:25 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: scanning -> associating Jan 19 04:17:27 ubuntu NetworkManager: <info> wlan0: link timed out. --- kern.log --- Jan 19 04:18:11 ubuntu kernel: [ 142.420024] wlan0: direct probe to AP 94:44:52:0d:22:0d timed out Jan 19 04:18:13 ubuntu kernel: [ 144.333847] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 1) Jan 19 04:18:13 ubuntu kernel: [ 144.539996] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 2) Jan 19 04:18:13 ubuntu kernel: [ 144.750027] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 3) Jan 19 04:18:14 ubuntu kernel: [ 144.940022] wlan0: direct probe to AP 94:44:52:0d:22:0d timed out Jan 19 04:18:25 ubuntu kernel: [ 155.832995] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 1) Jan 19 04:18:25 ubuntu kernel: [ 156.030046] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 2) Jan 19 04:18:25 ubuntu kernel: [ 156.230039] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 3) Jan 19 04:18:25 ubuntu kernel: [ 156.430039] wlan0: direct probe to AP 94:44:52:0d:22:0d timed out --- syslog --- Jan 19 04:18:46 ubuntu wpa_supplicant[1289]: Authentication with 94:44:52:0d:22:0d timed out. Jan 19 04:18:46 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: associating -> disconnected Jan 19 04:18:46 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: disconnected -> scanning Jan 19 04:18:48 ubuntu wpa_supplicant[1289]: WPS-AP-AVAILABLE Jan 19 04:18:48 ubuntu wpa_supplicant[1289]: Trying to associate with 94:44:52:0d:22:0d (SSID='Wuggawoo' freq=2437 MHz) Jan 19 04:18:48 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: scanning -> associating Jan 19 04:18:48 ubuntu kernel: [ 178.833905] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 1) Jan 19 04:18:48 ubuntu kernel: [ 179.030035] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 2) Jan 19 04:18:48 ubuntu kernel: [ 179.230020] wlan0: direct probe to AP 94:44:52:0d:22:0d (try 3) Jan 19 04:18:48 ubuntu kernel: [ 179.433634] wlan0: direct probe to AP 94:44:52:0d:22:0d timed out lspci and lsusb lspci -- 00:00.0 Host bridge: Advanced Micro Devices [AMD] RS780 Host Bridge 00:02.0 PCI bridge: Advanced Micro Devices [AMD] RS780 PCI to PCI bridge (ext gfx port 0) 00:05.0 PCI bridge: Advanced Micro Devices [AMD] RS780 PCI to PCI bridge (PCIE port 1) 00:06.0 PCI bridge: Advanced Micro Devices [AMD] RS780 PCI to PCI bridge (PCIE port 2) 00:11.0 SATA controller: ATI Technologies Inc SB700/SB800 SATA Controller [AHCI mode] 00:12.0 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI0 Controller 00:12.1 USB Controller: ATI Technologies Inc SB700 USB OHCI1 Controller 00:12.2 USB Controller: ATI Technologies Inc SB700/SB800 USB EHCI Controller 00:13.0 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI0 Controller 00:13.1 USB Controller: ATI Technologies Inc SB700 USB OHCI1 Controller 00:13.2 USB Controller: ATI Technologies Inc SB700/SB800 USB EHCI Controller 00:14.0 SMBus: ATI Technologies Inc SBx00 SMBus Controller (rev 3a) 00:14.1 IDE interface: ATI Technologies Inc SB700/SB800 IDE Controller 00:14.2 Audio device: ATI Technologies Inc SBx00 Azalia (Intel HDA) 00:14.3 ISA bridge: ATI Technologies Inc SB700/SB800 LPC host controller 00:14.4 PCI bridge: ATI Technologies Inc SBx00 PCI to PCI Bridge 00:14.5 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI2 Controller 00:18.0 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] HyperTransport Configuration 00:18.1 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Address Map 00:18.2 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] DRAM Controller 00:18.3 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Miscellaneous Control 00:18.4 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Link Control 01:00.0 VGA compatible controller: nVidia Corporation G80 [GeForce 8800 GTS] (rev a2) 02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 02) 03:00.0 FireWire (IEEE 1394): JMicron Technology Corp. IEEE 1394 Host Controller -- lsusb -- Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 003: ID 046d:c517 Logitech, Inc. LX710 Cordless Desktop Laser Bus 004 Device 002: ID 045e:0730 Microsoft Corp. Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 003: ID 13d3:3247 IMC Networks 802.11 n/g/b Wireless LAN Adapter Bus 002 Device 002: ID 0718:0628 Imation Corp. Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 003: ID 046d:08c2 Logitech, Inc. QuickCam PTZ Bus 001 Device 002: ID 0424:2228 Standard Microsystems Corp. 9-in-2 Card Reader Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub With no security on my router I still can't connect, I get: Jan 19 15:58:01 ubuntu wpa_supplicant[1165]: Authentication with 94:44:52:0d:22:0d timed out. Jan 19 15:58:01 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: associating -> disconnected Jan 19 15:58:01 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: disconnected -> scanning Jan 19 15:58:02 ubuntu wpa_supplicant[1165]: WPS-AP-AVAILABLE Jan 19 15:58:02 ubuntu wpa_supplicant[1165]: Trying to associate with 94:44:52:0d:22:0d (SSID='Wuggawoo' freq=2437 MHz) Jan 19 15:58:02 ubuntu wpa_supplicant[1165]: Association request to the driver failed Jan 19 15:58:02 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: scanning -> associating Jan 19 15:58:05 ubuntu NetworkManager: <info> wlan0: link timed out. Jan 19 15:58:07 ubuntu wpa_supplicant[1165]: Authentication with 94:44:52:0d:22:0d timed out. Jan 19 15:58:07 ubuntu NetworkManager: <info> (wlan0): supplicant connection state: associating -> disconnected Jan 19 15:58:07 ubuntu NetworkManager: <info> (wlan0): supplicant connec

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  • Woes of a Junior Developer - is it possible to not be cut out for programming?

    - by user575158
    (Let me start off by asking - please be gentle, I know this is subjective, but it's meant to incite discussion and provide information for others. If needed it can be converted to community wiki.) I recently was hired as a junior developer at a company I really like. I started out in the field doing QA and transitioned into more and more development work, which is what I really want to end up doing. I enjoy it, but more and more I am questioning whether I am really any good at it or not. Part of this is still growing into the junior developer role, I know, but how much? What are junior developers to expect, what should they be doing and not doing? What can I do to improve and show my company I am serious about this opportunity? I hate that I am costing them time by getting up to speed. I've been told by others that companies make investments in Junior devs and don't expect them to pay off for a while, but how much of this is true? There's got to be a point when it's apparent whether the investment will pay off or not. So far I've been trying to ask as many questions I can, but I've you've been obsessing over a simple problem for some time and the others know that, there comes a time when it's pretty embarrassing to have to get help after struggling so long. I've also tried to be as open to suggestion as possible and work with others to try to refactor my code, but sometimes this can be hard clashing with various team members' personal opinions (being told by someone to write it one way, and then having someone else make you rewrite it). I often get over-stressed and judge myself too harshly, but I just don't want to have to struggle the rest of my life trying to get things work if I just don't have the talent. In your experience, is programming something that almost everyone can learn, or something that some people just don't get? Do others feel this way, or did you feel that way when starting out? It scares me that I have no other job skills should I be unsuited for having the skills necessary to code well.

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  • Delegates and Events in C#

    - by hakanbilge
    Events and their underlying mechanism "Delegates" are very powerful tools of a developer and Event Driven Programming is one of the main Programming Paradigms. Its wiki definition is "event-driven programming or event-based programming is a programming paradigm in which the flow of the program is determined by events?i.e., sensor outputs or user actions (mouse clicks, key presses) or messages from other programs or threads." That means, your program can go its own way sequentially and in the case of anything that requires attention is done (when an event fires) by somebody or something, you can response it by using that event's controller method (this mechanism is like interrupt driven programming in embedded systems). There are many real world scenarios for events, for example, ASP.NET uses events to catch a click on a button or in your app, controller has notice of a change in UI by handling events exposed by view (in MVC pattern). Delegates in C# C# delegates correspond to function pointers in  [read more....]

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  • Can't get bonding and bridging to work for KVM

    - by user9546
    Hi everyone. I can't for the life of me get bonding and bridging to work for the KVM setup I'm building. I'm using a fresh install (not an upgrade) of Ubuntu Server 10.10. I have 4 NICs on the same subnet (two intended for each of my two VMs). I'm trying to achieve the setup that Uthark describes here. But following his guidelines didn't work for me. My eth0 and eth1 did not come up, and "brctl show" showed that br0 didn't have any interfaces (the bond). I assumed it didn't work because he's using 10.4, and this article says there's a recent change in bonding: [I can't post more than one hyperlink per post because I'm a newbie.] I had to use this article to get my interfaces to work at all on the same subnet, which is why I have the post-up lines on some of my interfaces: [I can't post more than one hyperlink per post because I'm a newbie.] I installed ifenslave and ethtool. I also created /etc/modprobe.d/aliases.conf with the following content: alias bond0 bonding options bonding mode=6 miimon=100 downdelay=200 updelay=200 And I included "bonding" in /etc/modules So, after several approaches, here is my latest interfaces file: auto lo iface lo inet loopback auto eth5 iface eth5 inet manual auto br5 iface br5 inet static post-up /sbin/ip rule add from [network].79 lookup 10 post-up /sbin/ip route add table 10 default via [network].1 src [network].79 dev br5 address [network].79 netmask 255.255.255.0 network [network].0 broadcast [network].255 gateway [network].1 bridge_ports eth5 bridge_stp off bridge_fd 0 bridge_maxwait 0 auto eth2 iface eth2 inet manual auto br2 iface br2 inet static post-up /sbin/ip rule add from [network].78 lookup 11 post-up /sbin/ip route add table 11 default via [network].1 src [network].78 dev br2 address [network].78 netmask 255.255.255.0 network [network].0 broadcast [network].255 gateway [network].1 bridge_ports eth2 bridge_stp off bridge_fd 0 bridge_maxwait 0 iface eth0 inet manual iface eth1 inet manual auto bond0 iface bond0 inet static bond_miimon 100 bond_mode balance-alb up /sbin/ifenslave bond0 eth0 eth1 down /sbin/ifenslave -d bond0 eth0 eth1 auto br0 iface br0 inet static address [network].60 netmask 255.255.255.0 network [network].0 broadcast [network].255 gateway [network].1 bridge_ports bond0 eth2, eth5, br2, and br5 all seem to be working fine. The only other thing I could find that looked suspicious is an error regarding bonding in /var/log/messages: kernel: [ 3.828684] bonding: Warning: either miimon or arp_interval and arp_ip_target module parameters must be specified, otherwise bonding will not detect link failures! see bonding.txt for details. even though there is a bond-miimon line in /etc/network/interfaces (if that's what they're talking about). Also, the bond seems to go in and out of promiscuous mode several times on boot: Jan 20 14:19:02 kvmhost kernel: [ 3.902378] device bond0 entered promiscuous mode Jan 20 14:19:02 kvmhost kernel: [ 3.902390] device bond0 left promiscuous mode Jan 20 14:19:02 kvmhost kernel: [ 3.902393] device bond0 entered promiscuous mode Jan 20 14:19:02 kvmhost kernel: [ 3.902397] device bond0 left promiscuous mode Jan 20 14:19:03 kvmhost kernel: [ 4.998990] device bond0 entered promiscuous mode Jan 20 14:19:03 kvmhost kernel: [ 4.999005] device bond0 left promiscuous mode Jan 20 14:19:03 kvmhost kernel: [ 4.999008] device bond0 entered promiscuous mode Jan 20 14:19:03 kvmhost kernel: [ 4.999012] device bond0 left promiscuous mode Any advice would be greatly appreciated. It seems that this must be possible, based on other posts, but I can't see what I'm doing wrong. Thanks.

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  • Converting a PV vm back into an HVM vm

    - by wim.coekaerts
    I have been doing some Oracle VM benchmark stuff in the last week or 2 in my off hours and yesterday I wanted to convert one of my VMs that was based on a paravirt kernel into a vm that just boots as a regular hardware virt VM with a standard x86-64 kernel. It took me a little while to figure out the fastest way so now that I have it pretty much down I wanted to share the steps. A PV kernel uses pygrub and a paravirt kernel image that lives on the vm image virtual disk. since this disk image does not have to be bootable it doesn't contain a boot sector and if you just restart the VM in hvm mode the virtual bios will just not do much as it can't start the boot process from disk The first thing I do is make a backup of my vm.cfg file :-) and then edit it as follows : the original file contains : bootloader = '/usr/bin/pygrub' I replace that with : acpi = 1 apic = 1 builder = 'hvm' device_model = '/usr/lib/xen/bin/qemu-dm' kernel = '/usr/lib/xen/boot/hvmloader' then changing the disk files. I change my xvd disks to hd disks and I copy over the iso image of my instal lDVD. In the case of my VM template it was based on OL5U4 So I downloaded Enterprise-R5-U4-Server-x86_64-dvd.iso and added it as a cd device. disk = ['file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/System.img,xvda,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Oracle11202RAC_x86_64-xvdb.img,xvdb,w', ] to disk = ['file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/System.img,hda,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Oracle11202RAC_x86_64-xvdb.img,hdb,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Enterprise-R5-U4-Server-x86_64-dvd.iso, hdc:cdrom,r', ] boot='d' for the network devices (vifs) I change : vif = ['bridge=xenbr2,type=netfront'] to vif = ['bridge=xenbr2,type=ioemu'] That should do it. Next, inside the VM, I copy over the regular kernel rpm that I want to end up running in hvm mode. In this example case it was : kernel-2.6.18-164.0.0.0.1.el5.x8664.rpm. I will use that later on in the process. I put this kernel simply in /root At this point I just start the vm with xm create vm.cfg and start my vnc console to the vm console. Oracle Linux will boot from the iso image, I just go through the install steps and click on UPgrade existing (not re-install). Because the VM is the same as the ISO the install won't actually do anything and it will run through instantly. When the "Reboot" button pops up, don't reboot. Switch to the command prompt console. hi alt-f2 to go to the shell prompt. Now it's easy : umount /mnt/sysimage/boot cd /mnt/sysimage chroot . mount /dev/hda1 (if that was your /boot partition) export PATH=/sbin:$PATH (just to clean that up) edit /etc/modprobe.conf and comment out the xen modules (just put a # in front) Install grub. if your /boot is hda1 then that is (hd0,0) $ grub root (hd0,0) setup (hd0) exit grub now you have a good bootsector, grub installed and you have your grub.conf file Install the new kernel cd root (this is your old /root in your pv image) rpm -ivh remove (or comment out) boot='d' in your vm.cfg restart the VM and you should be good to go, regular grub should start and load your environment. Caveats : this assumes you used labels for your filesystems. if /etc/fstab were to have devices listed then you would have to rename these device before rebooting as well. If you had a /dev/xvda disk then this would be /dev/hda or /dev/sda. All in all it is a relatively short and simple process.

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  • Converting a PV vm back into an HVM vm

    - by wim.coekaerts
    I have been doing some Oracle VM benchmark stuff in the last week or 2 in my off hours and yesterday I wanted to convert one of my VMs that was based on a paravirt kernel into a vm that just boots as a regular hardware virt VM with a standard x86-64 kernel. It took me a little while to figure out the fastest way so now that I have it pretty much down I wanted to share the steps. A PV kernel uses pygrub and a paravirt kernel image that lives on the vm image virtual disk. since this disk image does not have to be bootable it doesn't contain a boot sector and if you just restart the VM in hvm mode the virtual bios will just not do much as it can't start the boot process from disk The first thing I do is make a backup of my vm.cfg file :-) and then edit it as follows : the original file contains : bootloader = '/usr/bin/pygrub' I replace that with : acpi = 1 apic = 1 builder = 'hvm' device_model = '/usr/lib/xen/bin/qemu-dm' kernel = '/usr/lib/xen/boot/hvmloader' then changing the disk files. I change my xvd disks to hd disks and I copy over the iso image of my instal lDVD. In the case of my VM template it was based on OL5U4 So I downloaded Enterprise-R5-U4-Server-x86_64-dvd.iso and added it as a cd device. disk = ['file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/System.img,xvda,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Oracle11202RAC_x86_64-xvdb.img,xvdb,w', ] to disk = ['file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/System.img,hda,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Oracle11202RAC_x86_64-xvdb.img,hdb,w', 'file:/ovs/OVM_EL5U4_X86_64_11202RAC_PVM/Enterprise-R5-U4-Server-x86_64-dvd.iso, hdc:cdrom,r', ] boot='d' for the network devices (vifs) I change : vif = ['bridge=xenbr2,type=netfront'] to vif = ['bridge=xenbr2,type=ioemu'] That should do it. Next, inside the VM, I copy over the regular kernel rpm that I want to end up running in hvm mode. In this example case it was : kernel-2.6.18-164.0.0.0.1.el5.x8664.rpm. I will use that later on in the process. I put this kernel simply in /root At this point I just start the vm with xm create vm.cfg and start my vnc console to the vm console. Oracle Linux will boot from the iso image, I just go through the install steps and click on UPgrade existing (not re-install). Because the VM is the same as the ISO the install won't actually do anything and it will run through instantly. When the "Reboot" button pops up, don't reboot. Switch to the command prompt console. hi alt-f2 to go to the shell prompt. Now it's easy : umount /mnt/sysimage/boot cd /mnt/sysimage chroot . mount /dev/hda1 (if that was your /boot partition) export PATH=/sbin:$PATH (just to clean that up) edit /etc/modprobe.conf and comment out the xen modules (just put a # in front) Install grub. if your /boot is hda1 then that is (hd0,0) $ grub root (hd0,0) setup (hd0) exit grub now you have a good bootsector, grub installed and you have your grub.conf file Install the new kernel cd root (this is your old /root in your pv image) rpm -ivh remove (or comment out) boot='d' in your vm.cfg restart the VM and you should be good to go, regular grub should start and load your environment. Caveats : this assumes you used labels for your filesystems. if /etc/fstab were to have devices listed then you would have to rename these device before rebooting as well. If you had a /dev/xvda disk then this would be /dev/hda or /dev/sda. All in all it is a relatively short and simple process.

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  • University teaches DOS-style C++, how to deal with it

    - by gaidal
    Half a year ago I had a look at available programming educations. I chose this one because unlike most of the choices: The majority of the courses seemed to be about something concrete and useful; the languages used are C++ and Java which are platform-independent; later courses include developing for mobile devices and a course on Android development, which seemed modern and relevant. Now after two introductory courses we're just starting with C++, and my programming professor seems a bit weird. He's tested us on things like "why should you use constants" and "why are globals bad" in a kind of mechanical way, without much context, before teaching actual programming. His handouts use system("pause"), system("cls"), and getch() from some conio.h that seems ancient according to what I've read. I just did a task that was about printing the "ASCII letters from 32 to 255" (huh?), with an example picture showing a table with Windows' Extended ASCII - of course I got other results for 128-255 on my Arch Linux that uses Unicode, and this isn't mentioned at all. I don't know, it just doesn't seem right... As if he is teaching programming because he has to, perhaps? Should I bring such things up? Hmm. I was looking forward to learning from someone who really knows stuff, and in an academic, rigorous way, like SICP or something. Aren't professors in programming supposed to be like that? I studied math for a while and every teacher and assistant there were really precise about what they said, but this is my second programming teacher that is sort of disappointing. Oh well. Now, question: Is this what to expect from universities or Not OK, and how do I deal with it? I have never touched the language C++ (or C) until now, and am not the right person to jump up and say "This is So Wrong!", so if I google something and find 10 people who say "xxx is blasphemy", how do I skillfully communicate this? I do think it would be better for those classmates who are total beginners not to learn bad habits (such as these vibes of total ignorance of other platforms!) during the upcoming courses, but don't want to disrespect the teacher. I don't know if it's reasonable or just cocky to bring up things like "what about other platforms?" or "but what about this article or stackoverflow answer that I read that said..." for every assignment? Or, if he keeps ignoring non-Windows-programming, should I give up and focus on my own projects or somehow argue that this really isn't OK nowadays? Are there any programming teachers out there, what do you think? By the way these are web-based courses, all interaction between teachers and students takes place in a forum. EDIT: A few answers seem to be making some incorrect assumptions, so maybe I should add a few things. I have been doing programming for fun on and off for 10 years, am pretty comfortable in 3 languages and read programming blogs et c regularly. Also, I feel kind of done being a student, having a degree in another field. I just need another, relevant diploma to work as a programmer, so I'm going back for that. Studying computer science for 5 years is not for me anymore, even though I enjoy learning and solving problems in my free time. Second, let me highlight that I don't expect it to be like the industry at all, quite the contrary. I expect it to be academic, dry and unnecessarily correct. No, it's not just math. Every professor I have had in math, or Japanese (major) or Chinese (minor) have been very very academic, discussing subtle points for hours with passion. But the courses I'm taking now and a previous one in programming don't seem serious. They neither resemble industry NOR academia. That is the problem. And it's not because I can't learn programming anyway. Third, I don't necessarily want to learn C++ or Android development, and I know I could teach myself those and anything else if I wanted to. But I am going back to school anyway, and those platform-independent languages and mobile stuff made me think that maybe they're serious about teaching something relevant here. Seems like I got this wrong, but we'll see.

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  • yum update works but yum --security update fails to work in Fedora 12

    - by bobo
    I had already installed the yum-security before. And I was going to do an update by entering the following command: [root@localhost /]# yum update Loaded plugins: presto, priorities, refresh-packagekit, security Skipping security plugin, no data Setting up Update Process Resolving Dependencies Skipping security plugin, no data --> Running transaction check ---> Package eject.i686 0:2.1.5-17.fc12 set to be updated ---> Package glibc.i686 0:2.11.1-4 set to be updated ---> Package glibc-common.i686 0:2.11.1-4 set to be updated ---> Package glibc-devel.i686 0:2.11.1-4 set to be updated ---> Package glibc-headers.i686 0:2.11.1-4 set to be updated ---> Package gnome-themes.noarch 0:2.28.1-3.fc12 set to be updated ---> Package gtk2.i686 0:2.18.9-3.fc12 set to be updated ---> Package gtk2-immodule-xim.i686 0:2.18.9-3.fc12 set to be updated ---> Package kernel-PAE.i686 0:2.6.32.11-99.fc12 set to be installed ---> Package kernel-PAE-devel.i686 0:2.6.32.11-99.fc12 set to be installed ---> Package kernel-PAEdebug-devel.i686 0:2.6.32.11-99.fc12 set to be installed ---> Package kernel-debug-devel.i686 0:2.6.32.11-99.fc12 set to be installed ---> Package kernel-devel.i686 0:2.6.32.11-99.fc12 set to be installed ---> Package kernel-firmware.noarch 0:2.6.32.11-99.fc12 set to be updated ---> Package kernel-headers.i686 0:2.6.32.11-99.fc12 set to be updated ---> Package libnetfilter_conntrack.i686 0:0.0.101-1.fc12 set to be updated ---> Package media-player-info.noarch 0:5-1.fc12 set to be updated ---> Package nscd.i686 0:2.11.1-4 set to be updated ---> Package perf.noarch 0:2.6.32.11-99.fc12 set to be updated ---> Package rhythmbox.i686 0:0.12.6-5.fc12 set to be updated ---> Package sysvinit-tools.i686 0:2.87-3.dsf.fc12 set to be updated --> Finished Dependency Resolution --> Running transaction check ---> Package kernel-PAE.i686 0:2.6.31.12-174.2.3.fc12 set to be erased --> Finished Dependency Resolution Dependencies Resolved ================================================================================ Package Arch Version Repository Size ================================================================================ Installing: kernel-PAE i686 2.6.32.11-99.fc12 updates 20 M kernel-PAE-devel i686 2.6.32.11-99.fc12 updates 6.2 M kernel-PAEdebug-devel i686 2.6.32.11-99.fc12 updates 6.2 M kernel-debug-devel i686 2.6.32.11-99.fc12 updates 6.2 M kernel-devel i686 2.6.32.11-99.fc12 updates 6.1 M Updating: eject i686 2.1.5-17.fc12 updates 49 k glibc i686 2.11.1-4 updates 4.2 M glibc-common i686 2.11.1-4 updates 14 M glibc-devel i686 2.11.1-4 updates 953 k glibc-headers i686 2.11.1-4 updates 590 k gnome-themes noarch 2.28.1-3.fc12 updates 1.5 M gtk2 i686 2.18.9-3.fc12 updates 3.2 M gtk2-immodule-xim i686 2.18.9-3.fc12 updates 60 k kernel-firmware noarch 2.6.32.11-99.fc12 updates 968 k kernel-headers i686 2.6.32.11-99.fc12 updates 749 k libnetfilter_conntrack i686 0.0.101-1.fc12 updates 37 k media-player-info noarch 5-1.fc12 updates 32 k nscd i686 2.11.1-4 updates 189 k perf noarch 2.6.32.11-99.fc12 updates 79 k rhythmbox i686 0.12.6-5.fc12 updates 4.0 M sysvinit-tools i686 2.87-3.dsf.fc12 updates 58 k Removing: kernel-PAE i686 2.6.31.12-174.2.3.fc12 @updates 72 M Transaction Summary ================================================================================ Install 5 Package(s) Upgrade 16 Package(s) Remove 1 Package(s) Reinstall 0 Package(s) Downgrade 0 Package(s) Total download size: 75 M Is this ok [y/N]: But then I changed my mind, I decided to do a security-only update instead of a full update, so I entered the following command: [root@localhost /]# yum --security update Loaded plugins: presto, priorities, refresh-packagekit, security Setting up Update Process Resolving Dependencies Limiting packages to security relevant ones http://download.fedoraproject.org/pub/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.cuhk.edu.hk/pub/linux/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.cuhk.edu.hk/pub/linux/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.cuhk.edu.hk/pub/linux/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.riken.jp/Linux/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.riken.jp/Linux/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://mirror.cse.iitk.ac.in/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://mirror.cse.iitk.ac.in/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://mirrors.isu.net.sa/pub/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://mirrors.isu.net.sa/pub/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. ftp://ftp.chu.edu.tw/linux/Fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno -1] Metadata file does not match checksum Trying other mirror. http://mirror.yandex.ru/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://mirror.yandex.ru/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://linus.iyte.edu.tr/linux/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://linus.iyte.edu.tr/linux/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.jaist.ac.jp/pub/Linux/Fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.jaist.ac.jp/pub/Linux/Fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.kddilabs.jp/Linux/packages/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://srv2.ftp.ne.jp/Linux/packages/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://www.ftp.ne.jp/Linux/distributions/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://srv2.ftp.ne.jp/Linux/distributions/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.rhd.ru/pub/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.rhd.ru/pub/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://mirrors.163.com/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://mirrors.163.com/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://mirror.nus.edu.sg/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://mirror.nus.edu.sg/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.yz.yamagata-u.ac.jp/pub/linux/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.yz.yamagata-u.ac.jp/pub/linux/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.linux.org.tr/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.linux.org.tr/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://mirrors.cytanet.com.cy/linux/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://mirrors.cytanet.com.cy/linux/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://fedoramirror.hnsdc.com/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://fedoramirror.hnsdc.com/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.twaren.net/Linux/Fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://c147.twaren.net/pub/Linux/Fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.mirror.tw/pub/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.mirror.tw/pub/fedora/linux/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ftp.cs.pu.edu.tw/Linux/Fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ftp.cs.pu.edu.tw/Linux/Fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. http://ubuntu.cn99.com/fedora/updates/12/i386/repodata/updateinfo.xml.gz: [Errno 14] HTTP Error 416 : http://ubuntu.cn99.com/fedora/updates/12/i386/repodata/updateinfo.xml.gz Trying other mirror. Error: failure: repodata/updateinfo.xml.gz from updates: [Errno 256] No more mirrors to try. You could try using --skip-broken to work around the problem ^C[root@localhost /]# As it can be seen in the output, when I run the yum --security update command, it did show the Limiting packages to security relevant ones message so it's aware of the option. But I don't know why it keeps reporting the http error 416. I searched in google and found the following description of the error but it doesn't seem to help much. HTTP ERROR 416 - Requested Range Not Satisfiable A 416 status code indicates that the server was unable to fulfill the request. This may be, for example, because the client asked for the 800th-900th bytes of a document, but the document was only 200 bytes long. It suggests me to use the --skip-broken option, I tried and the output is the same. I already tested many times, it just doesn't work when the --security option is used. What could be the possible cause for this problem?

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  • Problems with repositories on CentOS 3.9

    - by rodnower
    Hello, I have CentOS 3.9 for i386. When I try to instal some thing with yum, i.e: yum install firefox or yum install firefox* or yum list firefox and so on, I get: +++++++++++++++++++ yum info firefox Gathering header information file(s) from server(s) Server: CentOS-3 - Addons Server: CentOS-3 - Base Server: CentOS-3 - Extras Server: CentOS-3 - Updates Server: Jason's Utter Ramblings Repo Finding updated packages Downloading needed headers Looking in Available Packages: Looking in Installed Packages: +++++++++++++++++++ Some time ago I had CentOS 5, and I had the similar problem (exept of firefox all other packages were not installed) and I spent very much time to find different repositories and so on. Now I have CentOS 3, and there is nothing I can install with yum. This is yum.conf content: +++++++++++++++++++ [main] cachedir=/var/cache/yum debuglevel=2 logfile=/var/log/yum.log pkgpolicy=newest distroverpkg=redhat-release installonlypkgs=kernel kernel-smp kernel-hugemem kernel-enterprise kernel-debug kernel-unsupported kernel-smp-unsupported kernel-hugemem-unsupported tolerant=1 exactarch=1 [utterramblings] name=Jason's Utter Ramblings Repo baseurl=http://www.jasonlitka.com/media/EL4/i386/ [base] name=CentOS-$releasever - Base baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/ #released updates [update] name=CentOS-$releasever - Updates baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/ #packages used/produced in the build but not released [addons] name=CentOS-$releasever - Addons baseurl=http://mirror.centos.org/centos/$releasever/addons/$basearch/ #additional packages that may be useful [extras] name=CentOS-$releasever - Extras baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/ #[centosplus] #name=CentOS-$releasever - Plus #baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/ #[testing] #name=CentOS-$releasever - Testing #baseurl=http://mirror.centos.org/centos/$releasever/testing/$basearch/ #[fasttrack] #name=CentOS-$releasever - Fasttrack #baseurl=http://mirror.centos.org/centos/$releasever/fasttrack/$basearch/ +++++++++++++++++++ The file is too long, so I littely edited it. So my question is: is there some "normal" one repository that have all basic thing like firefox and so that I will insert to this file and all will work fine? Thank you very much for ahead.

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  • Configure IPv6 routing

    - by godlark
    I've got IPv6 addresses from SIXXS. My host is connected with SIXXS network over a AICCU tunnel ("sixxs" interface). My host address is 2001:::2, the host on the end has address 2001:::1. On my host IPv6 is fully accessible. I have problem with configuring IPv6 network on VMs. I use VirtualBox, the VM (Ubuntu) uses tap1 (on the host bridged by br0) #!/bin/sh PATH=/sbin:/usr/bin:/bin:/usr/bin:/usr/sbin # create a tap tunctl -t tap1 ip link set up dev tap1 # create the bridge brctl addbr br0 brctl addif br0 tap1 # set the IP address and routing ip link set up dev br0 ip -6 route del 2001:6a0:200:172::/64 dev sixxs ip -6 route add 2001:6a0:200:172::1 dev sixxs ip -6 addr add 2001:6a0:200:172::2/64 dev br0 ip -6 route add 2001:6a0:200:172::2/64 dev br0 Host: routing table: 2001:6a0:200:172::1 dev sixxs metric 1024 2001:6a0:200:172::/64 dev br0 proto kernel metric 256 2001:6a0:200:172::/64 dev br0 metric 1024 2000::/3 dev sixxs metric 1024 fe80::/64 dev eth0 proto kernel metric 256 fe80::/64 dev sixxs proto kernel metric 256 fe80::/64 dev br0 proto kernel metric 256 fe80::/64 dev tap1 proto kernel metric 256 default via 2001:6a0:200:172::1 dev sixxs metric 1024 Guest: interface eth1 (it is connected with tap1): auto eth1 iface eth1 inet6 static address 2001:6a0:200:172::3 netmask 64 gateway 2001:6a0:200:172::2 Guest: routing table 2001:6a0:200:172::/64 dev eth1 proto kernel metric 256 fe80::/64 dev eth0 proto kernel metric 256 fe80::/64 dev eth1 proto kernel metric 256 default via 2001:6a0:200:172::2 dev eth1 metric 1024 The guest pings to the host, the host pings to the guest, the host pings to 2001:6a0:200:172::1, but the guest doesn't ping to 2001:6a0:200:172::1. The guest tries to ping, on the host (by tcdump) I can capture its packets, but the host doesn't send them to 2001:6a0:200:172::1. What have I missed in configuration?

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  • How to get the permissions right for /dev/raw1394

    - by Mark0978
    I recently upgraded one of my ubuntu machines to Karmic and I'm having trouble getting the permissions of /dev/raw1394 set to 0666. They only thing this machine is used for is recording audio from a firepod which uses /dev/raw1394 via jackd and there are no other FireWire devices connected, so security around this device is not really an issue. If I run as root, everything works as expected, but I have some folks that run the recorder that I don't want to have root access. However, I can't figure out which lines setup the perms I've tied this: /etc/udev/permissions.d/raw1394.rules:raw1394:root:root:0666 And I have this setup (default install) /lib/udev/rules.d/75-persistent-net-generator.rules:SUBSYSTEMS=="ieee1394", ENV{COMMENT}="Firewire device $attr{host_id})" /lib/udev/rules.d/75-cd-aliases-generator.rules:# the "path" of usb/ieee1394 devices changes frequently, use "id" /lib/udev/rules.d/75-cd-aliases-generator.rules:ACTION=="add", SUBSYSTEM=="block", SUBSYSTEMS=="usb|ieee1394", ENV{ID_CDROM}=="?*", ENV{GENERATED}!="?*", \ /lib/udev/rules.d/60-persistent-storage-tape.rules:KERNEL=="st*[0-9]|nst*[0-9]", ATTRS{ieee1394_id}=="?*", ENV{ID_SERIAL}="$attr{ieee1394_id}", ENV{ID_BUS}="ieee1394" /lib/udev/rules.d/50-udev-default.rules:# FireWire (deprecated dv1394 and video1394 drivers) /lib/udev/rules.d/50-udev-default.rules:KERNEL=="dv1394-[0-9]*", NAME="dv1394/%n", GROUP="video" /lib/udev/rules.d/50-udev-default.rules:KERNEL=="video1394-[0-9]*", NAME="video1394/%n", GROUP="video" /lib/udev/rules.d/60-persistent-storage.rules:KERNEL=="sd*[!0-9]|sr*", ATTRS{ieee1394_id}=="?*", SYMLINK+="disk/by-id/ieee1394-$attr{ieee1394_id}" /lib/udev/rules.d/60-persistent-storage.rules:KERNEL=="sd*[0-9]", ATTRS{ieee1394_id}=="?*", SYMLINK+="disk/by-id/ieee1394-$attr{ieee1394_id}-part%n" And I find these lines in /var/log/syslog Apr 30 09:11:30 record kernel: [ 3.284010] ieee1394: Node added: ID:BUS[0-00:1023] GUID[000a9200c7062266] Apr 30 09:11:30 record kernel: [ 3.284195] ieee1394: Host added: ID:BUS[0-01:1023] GUID[00d0035600a97b9f] Apr 30 09:11:30 record kernel: [ 18.372791] ieee1394: raw1394: /dev/raw1394 device initialized What I can't figure out, is which line actually creates that raw1394 device in the first place. How do you get /dev/raw1394 to have permissions 0666?

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  • Ubuntu 10.04: Unable to Start RabbitMQ Server Post-Installation

    - by Garland W. Binns
    After installing RabbitMQ on Ubuntu 10.04 I receive a failure message that the service was unable to start. Any insight into the issue would be greatly appreciated! Below are contents of startup_log and startup_err. Startup_log: {error_logger,{{2012,7,7},{15,50,31}},"Protocol: ~p: register error: ~p~n",["inet_tcp",{{badmatch,{error,etimedout}},[{inet_tcp_dist,listen,1},{net_kernel,start_protos,4},{net_kernel,start_protos,3},{net_kernel,init_node,2},{net_kernel,init,1},{gen_server,init_it,6},{proc_lib,init_p_do_apply,3}]}]} {error_logger,{{2012,7,7},{15,50,31}},crash_report,[[{initial_call,{net_kernel,init,['Argument__1']}},{pid,<0.20.0>},{registered_name,[]},{error_info,{exit,{error,badarg},[{gen_server,init_it,6},{proc_lib,init_p_do_apply,3}]}},{ancestors,[net_sup,kernel_sup,<0.9.0>]},{messages,[]},{links,[#Port<0.100>,<0.17.0>]},{dictionary,[{longnames,false}]},{trap_exit,true},{status,running},{heap_size,987},{stack_size,24},{reductions,512}],[]]} {error_logger,{{2012,7,7},{15,50,31}},supervisor_report,[{supervisor,{local,net_sup}},{errorContext,start_error},{reason,{'EXIT',nodistribution}},{offender,[{pid,undefined},{name,net_kernel},{mfa,{net_kernel,start_link,[[rabbitmqprelaunch877,shortnames]]}},{restart_type,permanent},{shutdown,2000},{child_type,worker}]}]} {error_logger,{{2012,7,7},{15,50,31}},supervisor_report,[{supervisor,{local,kernel_sup}},{errorContext,start_error},{reason,shutdown},{offender,[{pid,undefined},{name,net_sup},{mfa,{erl_distribution,start_link,[]}},{restart_type,permanent},{shutdown,infinity},{child_type,supervisor}]}]} {error_logger,{{2012,7,7},{15,50,31}},std_info,[{application,kernel},{exited,{shutdown,{kernel,start,[normal,[]]}}},{type,permanent}]} {"Kernel pid terminated",application_controller,"{application_start_failure,kernel,{shutdown,{kernel,start,[normal,[]]}}}"} Startup_err: Crash dump was written to: erl_crash.dump Kernel pid terminated (application_controller) ({application_start_failure,kernel,{shutdown,{kernel,start,[normal,[]]}}})

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  • cups log kills ubuntu 12.04 and sudoer permissions changed

    - by peterretief
    I am using Ubuntu 12.04 as a desktop and recently had a weird crash with the log file for cups filling up the entire drive and not letting me back in, also what changed was /var/lib/sudo had changed from root to peter (me) I didn't make this change - I checked the history! I set the sudoers back to root and capped the max size for cups log Anyone had a similar experience? It feels like someone is messing around with my settings Is there any way to trace how the error occurred? Logs auth.log Jan 1 02:04:13 peter-desktop lightdm: pam_unix(lightdm:session): session opened for user lightdm by (uid=0) Jan 1 02:04:13 peter-desktop lightdm: pam_ck_connector(lightdm:session): nox11 mode, ignoring PAM_TTY :0 Jan 1 02:06:53 peter-desktop lightdm: pam_unix(lightdm:session): session opened for user lightdm by (uid=0) Jan 1 02:06:53 peter-desktop lightdm: pam_ck_connector(lightdm:session): nox11 mode, ignoring PAM_TTY :0 syslog Jan 1 02:04:13 peter-desktop rsyslogd: [origin software="rsyslogd" swVersion="5.8.6" x-pid="903" x-info="http://www.rsyslog.com"] start Jan 1 02:04:13 peter-desktop rsyslogd: rsyslogd's groupid changed to 103 Jan 1 02:04:13 peter-desktop rsyslogd: rsyslogd's userid changed to 101 Jan 1 02:04:13 peter-desktop rsyslogd-2039: Could not open output pipe '/dev/xconsole' [try http://www.rsyslog.com/e/2039 ] Jan 1 02:04:13 peter-desktop bluetoothd[898]: Failed to init gatt_example plugin Jan 1 02:04:13 peter-desktop kernel: [ 0.000000] Initializing cgroup subsys cpuset Jan 1 02:04:13 peter-desktop kernel: [ 0.000000] Initializing cgroup subsys cpu Jan 1 02:04:13 peter-desktop kernel: [ 0.000000] Linux version 3.2.0-25-generic-pae (buildd@palmer) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #40-Ubuntu SMP Wed May 23 22:11:24 UTC 2012 (Ubuntu 3.2.0-25.40-generic-pae 3.2.18) Jan 1 02:04:13 peter-desktop kernel: [ 0.000000] KERNEL supported cpus: Jan 1 02:04:13 peter-desktop kernel: [ 0.000000] Intel GenuineIntel Jan 1 02:04:13 peter-desktop kernel: [ 0.000000] AMD AuthenticAMD Jan 1 02:04:13 peter-desktop kernel: [ 0.000000] NSC Geode by NSC

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  • ios7 loops on the "trust this computer" dialog

    - by gcb
    trying to transfer files to the work ipad via my debian7 box. When i plug it on the computer usb port, it shows the dialog about trusting this computer, and the computer shows a gnome alert about the ipad being locked and that i should unlock it and try again. i press "trust" on the ipad and try again on gnome. and it starts again. over and over. endlessly. there are dozen threads about this on apple support forums. no solution. just dozens of "me too" flags. e.g. https://discussions.apple.com/message/23082859#23082859 (44 me-too, 2k views) here is the log/messages i get Oct 23 21:17:39 dotmatrix kernel: [ 1928.517766] usb 2-1.7: USB disconnect, device number 16 Oct 23 21:17:39 dotmatrix kernel: [ 1928.715441] usb 2-1.7: new high-speed USB device number 17 using ehci_hcd Oct 23 21:17:40 dotmatrix kernel: [ 1928.811031] usb 2-1.7: New USB device found, idVendor=05ac, idProduct=12ab Oct 23 21:17:40 dotmatrix kernel: [ 1928.811036] usb 2-1.7: New USB device strings: Mfr=1, Product=2, SerialNumber=3 Oct 23 21:17:40 dotmatrix kernel: [ 1928.811039] usb 2-1.7: Product: iPad Oct 23 21:17:40 dotmatrix kernel: [ 1928.811041] usb 2-1.7: Manufacturer: Apple Inc. Oct 23 21:17:40 dotmatrix kernel: [ 1928.811043] usb 2-1.7: SerialNumber: fec5e0f6a6fa18a936de3c53af661051d290275e Oct 23 21:17:40 dotmatrix mtp-probe: checking bus 2, device 17: "/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.7" Oct 23 21:17:40 dotmatrix mtp-probe: bus: 2, device: 17 was not an MTP device Oct 23 21:17:43 dotmatrix kernel: [ 1932.346505] usb 2-1.7: USB disconnect, device number 17 If i never press the trust dialog it will stay there until i remove the cable. but the logs shows that it gave up 3sec after the cable was connected.

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  • Preventing DDOS/SYN attacks (as far as possible)

    - by Godius
    Recently my CENTOS machine has been under many attacks. I run MRTG and the TCP connections graph shoots up like crazy when an attack is going on. It results in the machine becoming inaccessible. My MRTG graph: mrtg graph This is my current /etc/sysctl.conf config # Kernel sysctl configuration file for Red Hat Linux # # For binary values, 0 is disabled, 1 is enabled. See sysctl(8) and # sysctl.conf(5) for more details. # Controls IP packet forwarding net.ipv4.ip_forward = 0 # Controls source route verification net.ipv4.conf.default.rp_filter = 1 # Do not accept source routing net.ipv4.conf.default.accept_source_route = 0 # Controls the System Request debugging functionality of the kernel kernel.sysrq = 1 # Controls whether core dumps will append the PID to the core filename # Useful for debugging multi-threaded applications kernel.core_uses_pid = 1 # Controls the use of TCP syncookies net.ipv4.tcp_syncookies = 1 # Controls the maximum size of a message, in bytes kernel.msgmnb = 65536 # Controls the default maxmimum size of a mesage queue kernel.msgmax = 65536 # Controls the maximum shared segment size, in bytes kernel.shmmax = 68719476736 # Controls the maximum number of shared memory segments, in pages kernel.shmall = 4294967296 net.ipv4.conf.all.rp_filter = 1 net.ipv4.tcp_syncookies = 1 net.ipv4.icmp_echo_ignore_broadcasts = 1 net.ipv4.conf.all.accept_redirects = 0 net.ipv6.conf.all.accept_redirects = 0 net.ipv4.conf.all.send_redirects = 0 net.ipv4.conf.all.accept_source_route = 0 net.ipv4.conf.all.rp_filter = 1 net.ipv4.tcp_max_syn_backlog = 1280 Futher more in my Iptables file (/etc/sysconfig/iptables ) I only have this setup # Generated by iptables-save v1.3.5 on Mon Feb 14 07:07:31 2011 *filter :INPUT ACCEPT [1139630:287215872] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [1222418:555508541] Together with the settings above, there are about 800 IP's blocked via the iptables file by lines like: -A INPUT -s 82.77.119.47 -j DROP These have all been added by my hoster, when Ive emailed them in the past about attacks. Im no expert, but im not sure if this is ideal. My question is, what are some good things to add to the iptables file and possibly other files which would make it harder for the attackers to attack my machine without closing out any non-attacking users. Thanks in advance!

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  • SSH Interactive mode not working

    - by Ekin Koc
    I have a Debian based linux server running for a year or so, without any problems. A couple of days ago, ssh interactive mode stopped working for no reason. I mean, I can open an ssh connection just fine, the server greets me with shell but I just can't type anything. However, if I send commands like this: ssh [email protected] cat /var/log/messages, I get the response. I dug through several logs and found one message, which feels remotely relevant to the problem; sh kernel: [10222733.062511] ------------[ cut here ]------------ sh kernel: [10222733.062522] WARNING: at /build/buildd-linux-2.6_2.6.32-39-amd64-7yVIH2/linux-2.6-2.6.32/debian/build/source_amd64_none/drivers/char/tty_ldisc.c:738 tty_ldisc_reinit+0x46/0x7b() sh kernel: [10222733.062526] Hardware name: PowerEdge R210 II sh kernel: [10222733.062528] Modules linked in: ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_conntrack nf_defrag_ipv4 ip_tables x_tables sha1_generic arc4 ecb ppp_mppe ppp_async crc_ccitt ppp_generic slhc loop snd_pcm snd_timer snd soundcore snd_page_alloc i2c_i801 i2c_core pcspkr evdev joydev dcdbas container button processor ext3 jbd mbcache sg sd_mod sr_mod crc_t10dif cdrom usb_storage usbhid hid mpt2sas ahci ehci_hcd libata scsi_transport_sas usbcore bnx2 nls_base scsi_mod fan thermal thermal_sys [last unloaded: scsi_wait_scan] sh kernel: [10222733.062568] Pid: 8662, comm: sshd Not tainted 2.6.32-5-amd64 #1 sh kernel: [10222733.062569] Call Trace: sh kernel: [10222733.062572] [<ffffffff811ff056>] ? tty_ldisc_reinit+0x46/0x7b sh kernel: [10222733.062574] [<ffffffff811ff056>] ? tty_ldisc_reinit+0x46/0x7b Is there any way to get back the sshd working in interactive mode? I tried restarting sshd but that is no help. And somehow, I can not reboot the server. Tried sending shutdown -r now and reboot but it refuses to go down. Should I go ahead and request a physical reboot?

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  • clocksource tsc unstable

    - by amorfis
    Ok, now I have real server fault ;) After some time from booting (about one minute) my server hangs. All I can do is hard reset. Then after restart in /var/log/kern.log I can find: Jul 29 22:38:57 leonidas kernel: [ 90.729598] longhaul: Failed to set requested frequency! Jul 29 22:38:57 leonidas kernel: [ 90.731252] longhaul: Enabling "Ignore Revision ID" option. Jul 29 22:38:57 leonidas kernel: [ 91.201461] longhaul: Failed to set requested frequency! Jul 29 22:38:57 leonidas kernel: [ 91.201482] longhaul: Disabling ACPI C3 support. Jul 29 22:38:57 leonidas kernel: [ 91.204230] longhaul: Disabling "Ignore Revision ID" option. Jul 29 22:38:58 leonidas kernel: [ 91.416133] longhaul: Failed to set requested frequency! Jul 29 22:38:58 leonidas kernel: [ 91.416152] longhaul: Enabling "Ignore Revision ID" option. Jul 29 22:38:58 leonidas kernel: [ 91.960048] Clocksource tsc unstable (delta = -105611479 ns) I found some resources on the net, and it said to change clocksource, or disable ACPI. I tried disabling ACPI but it didn't help (but I noticed there was longer time before hanging). I can't change clock to hpet, because my system doesn't have such one. Output of cat /sys/devices/system/clocksource/clocksource0/available_clocksource: acpi_pm jiffies tsc My system is ubuntu server on VIA Epia hardware.

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