• Disable SSH Password Authentication to Increase Security and Harden SSH Linux Unix Server Ubuntu Mint Centos Debian


    Just a note before you do this you should have a sure, guaranteed way into the system such as local, KVMor preferably publickey making bruteforce SSH absolutely impossible since there is no password to bruteforce and even if someone knew the password they wouldn't be able to login except from the local console (presumably you should make sure no one unauthorized has physical access). 1. Edit /etc/ssh/sshd_config Find the section like this:........
  • ubuntu Linux colour dropper picker


    gpick is a great and simple tool now that I now how to use it sudo apt-get install gpick The trick is to find "the swatch" I was in a rush and was frustrated that it wouldn't work how Iexpected and I had to memorize the hex code of the color my mouse was over. There is something it tells you to do which is "Click on the swatch area" (click onthe honeycomb graphic area that is the s........
  • forcedeth MCP55 Nforce3600 Nvidia Network NIC Card Not working in Linux at 1gigabit speeds


    Now many people report this card simply not working in various Linux distros and kernels. My issue is different, it always works at 100mbit (eg. plugged into a 100mbit switch) but no matter what 1000M/gigabit switch I would try, it would never work. The link would be up (the lights were on) and the OS detected the link as being up as well but it wouldn't work at all and could not pass data in or out (not even a ack/ping). There is one simple solution and command........
  • Acer Aspire E1-522-5603 Howto Enter BIOS - Press F2


    Press F2, you wouldn't know this because like most new computers, it doesn't announce the required key unless you enable it from the BIOS. ........
  • Asterisk VOIP Sipura/Linksys PAP2T Calls Not Being Received Solution


    This problem seemed to happen recently but was likely causing issues before where the phone(s) do not ring. Now there are a few reasons why this can happen especially if your adapter has DND mode enabled (disable it). However that wasn't my issue and Ionly figured it out the other day when by fluke if you're on the phone (making a call) then calls will come in. That's when Ifigured out the solution: This likely app........
  • Dell SAS 6/ir Cards are just LSi 1068E cards


    02:00.0 SCSI storage controller: LSI Logic / Symbios Logic SAS1068E PCI-Express Fusion-MPT SAS (rev 08) 03:00.0 SCSI storage controller: LSI Logic / Symbios Logic SAS1068E PCI-Express Fusion-MPT SAS (rev 08) Basically these cards are a stripped-down version of Dell Perc 6/i only they (SAS 6/ir) support JBOD. The DellPerc 6/i are basically useless because it doesn't have JBOD support and requires software or BIOS commands to add or remove........
  • The Importance of a High Quality Power Supply/Power Supplies To Prevent Overheating/System Crash/Hardware Damage


    For years I've always built cheap systems believing that there is little difference in more expensive components when it comes to reliability and quality, I generally believe this still except for Power Supplies. I've always bought cheap cases with nice sounding 350-550W stock/cheap/crap power supplies and haven't had any issues for the most part until recently. One such case is an NGEAR case with a 550W Optimax power supply, I always read that these supplies don't produce the........
  • ifup eth0 SIOCSIFFLAGS: Cannot allocate memory Failed to bring up eth0 Centos Network won't work after kernel update and reboot


    ifup eth0 SIOCSIFFLAGS: Cannot allocate memory Failed to bring up eth0 This is on a Centos 5.5 machine with OpenVZ kernel 2.6.18-238.12.1.el5.028stab091.1PAE, I updated 3 systems with the same hardware to the same kernel and for some reason the network didn't come back. This only happened once the first time I booted into the new kernel and hasn't happened again but this is a serious issue for those running systems from remote locations such as a datacente........
  • Kernel/make compilation time and how to improve compile times/compile the Linux kernel faster without hardware upgrades


    I thought only a faster CPUand SSDwould help but I already have a Quad-Core CPU and it wasn't being maxed out. The actual tests were performed on an AMD-V enabled 128MB dual core VMWare container though. There is a flag that can be passed to make in order to start multiple threads, by specifying 4 threads I was able to reduce the whole kernel compilation time from scratch by about 50%! (65minutes vs 31minutes!). *Yes I did do a make clean before each co........
  • VBox/Virtualbox how to shrink VDI image and recover/reclaim unused disk space


    VBoxManage modifyvdi /path/to/your.vdi compact I believe this should be done only when your VM is powered off, but I decided to try it with the system powered on. i wouldn't recommend it because it's dangerous even if it does work but this is a test system. For anything important/production I would always take a backup first and make sure the system is powered off. VBoxManage modifyvdi XP-clone.vdi compact 0%...10%...20%...30%...40%...5........
  • Apache Crash Solution Can't Restart Due to Socket In use - (98)Address already in use: make_sock: could not bind to address [::]:80 (98)Address already in use: make_sock: could not bind to address 0.0.0.0:80 no listening sockets available, shutting d


    (98)Address already in use: make_sock: could not bind to address [::]:80 (98)Address already in use: make_sock: could not bind to address 0.0.0.0:80 no listening sockets available, shutting down This will even trip you up if you have a service like monit to save you if httpd crashes. The only way to fix this is to either wait (it's not an option for production situations) or to kill the ghost httpd processes that wouldn't gracefully close: So........
  • Virtualbox Guest Hang/Freeze Ghost Zombie VM Machine Problem/Solution


    Virtualbox hang problem A VM just froze and wouldn't close so I had to force it, but the VBox GUI thinks it's running even when I close it. I manually killed the related process by doing ps aux|grep VirtualBox and found the PID 6191 I killed it with "kill -kill 6191" but it remains open and as "defunct" so I can't restart it because the GUI freezes when I click on it because it thinks it is running still........
  • htaccess modrewrite problem with rewriting url with- dashes solution


    I was getting frustrated with trying to write a simple URL like this: /example-withdash I used the htaccess code like this: Rewriterule ^example-withdash$ / [R=301] I also tried escaping the dash which I thought should have treated it as a literal but that didn't work either: Rewriterule ^example-withdash$ / [R=301] But it wouldn't work, apparently the "-" dash means don't substitute,........
  • diff: memory exhausted


    I don't have a solution other than to use rsync, I used diff on about 1.7TB of data which includes hundreds of thousands if not millions of small files to ensure nothing was missing or corrupt. diff didn't even get past the first large directory without spitting that error out. Keep in mind I used "diff -r" because that means recursive, otherwise it wouldn't compare all files and subdirectories and would be a false way of doing it.........
  • 95th Percentile Billing vs Usage Billing, what's better?


    There are all kinds of threads and links on the internet, and this seems to be a contentious issue butI don't know why. 95th percentile is either a good deal for some or a big rip off for others, Ijust said it there :) But the reality is that for MOST people who transfer low amounts of data but burst to higher speeds such as 40mbit+ even for short periods of time, then you'll pay a lot of money to do that. Basically 95th percentile is an-old archaic method........
  • mdadm Centos 5 automatic resync


    This made me nervous but it's clearly a cronjob based on the messages log that happens every Sunday at about 4:22. I actually can't find any evidence of it in cron.d cron.daily but it is there somewhere obviously. What I don't get is why doesn't this cronjob do a datacheck like Ubuntu's cronscript does? When you unnecessarily rebuild the array you lose your redundancy during that point which makes your data extremely vulnerable. *Update I did a grep of &q........
  • VirtualBox Convert Import/Boot .vmdk VMWare Hard Disk/Drive Image Won't Work


    I wanted to Import/Use a .vmdk hard disk image file from VMWare. Generally you can just "point" VirtualBox to it and use it and it will work but I found an exception. One of my Centos 4.4 x64 images wouldn't boot. I had two copies, an older one and the newer one. The older one booted as normal (once I changed the VirtualBox driver to IDE from SATA). The newer one stopped at the "GRUB loading" message no matter what I tried. As far as........
  • mdadm RAID 1 adventures


    I separated the 2 drives in the RAID 1 array. 1 is the old one /dev/sda and is out of date, while the separated other one /dev/sdc was in another drive and mounted and used with more data (updated). I wonder how mdadm will handle this: usb-storage: device scan complete md: md127 stopped. md: bind md: md127: raid array is not clean -- starting background reconstruction raid1: raid set md127 active with 1 out of 2 m........
  • PHP Email Attachment Corrupt Solution


    I couldn't figure out why this wouldn't work, a test script in the root of my htdocs folder worked fine. Within some subdirectories the same code would produce different base64 results but I didn't know hwy. Archive: /tmp/archive.zip Zip file size: 6888 bytes, number of entries: 92 error [/tmp/archive.zip]: missing 242827681 bytes in zipfile (attempting to process anyway) error [/tmp/archive.zip]: attempt........
  • Wine stopped working/won't work Solution


    After an upgrade wine wouldn't open anything, not even the pre-installed notepad. There are no wine logs and nothing is mentioned in any standard log file about why. I finally decided to run wine from the shell and see what's going on: wine client error:0: version mismatch 398/402. Your wineserver binary was not upgraded correctly, or you have an older one somewhere in your PATH. Or maybe the wrong wineserver is still running?........
  • Nautilus/GNOME/Ubuntu File Manager not applying appearance style/changes


    I thought it was a GNOME problem because no matter what styles I applied Nautilus wouldn't change, but it was only Nautilus that wouldn't change/update anymore so I should have known. The only fix/solutionI knew of other than rebooting is the following: sudo killall nautilus I tried closing all instances of nautilus that were visible and it had no effect. And another thing to remember is that only will appearances/styles/themes not apply to N........
  • VirtualBox/VBOX Centos 5.5 Installation Kernel Freeze Problem "NET: Registered protocol family 2" And Solution


    NET: Registered protocol family 2 The above is the last thing that I ever saw, I tried pci=routeirq etc.. and it wouldn't work. The solution is to enable IOAPIC in the VBOX Settings Just enable "IOAPIC" in the settings for your Centos Guest and you'll find the kernel boots just fine. I wonder if a physical system might stall in this same way if the BIOS has IOAPIC disabled which many people do as a troubleshooting method. ........
  • rsync my favorite/best/optimal default switches and options


    Not sure what rsync switches/options to use? rsync -PDrphogtl The short version would be: rsync -Pha I think these are really common sense options to use and probaby should be the default. Explanation of rsync switches P = display the progress D = hybrid of --specials and --devices so all special and device files will be copied as well. r = recursive (otherwise rsync won't copy files deeper than........
  • tar DON't strip/add leading slashes


    It is desirable to strip the leading slashes when taring / because you wouldn't want to overwrite your entire system when extracting some files to check. But if you are restoring / from the tar you want the leading slashes added again. Here's how to do it: --absolute-names -P Either one above will do the same thing.........
  • MySQL TEXT field size length limit reminder, don't truncate your data!


    I thought there would be an error message or warning from MySQL in the case that the text you submit is greater than the allowed limit based on the field. So essentially I submitted text that was about 120,000 characters long, whereas the limit of TEXT is just 65,535 characters! I almost lost half of my data/what I typed without knowing it! I just altered the field type in my database from TEXT to LONGTEXT. I can't see how LONGTEXT wouldn't be long enough for MOST........
  • Problems surfing web/serving


    Problems surfing web/servingI noticed sometimes websites wouldn't load at random through a FreeBSD box and other systems on the same link didn't have the issue. I believe it is because of the low default limit of 128 TCP connections that caused the problem. It would also slow down any traffic that requires many connections such as Bittorrent. The fix is to increase the amount of connections to at least 1024 Edit [b:520b050d3e]/etc/sysctl.conf[/b:520b05........
  • Upgrade Release Kernel Tips


    Upgrade Release Kernel TipsThis is for CentOS 3.1 to 3.8 but the methodology will apply everywhere. I ran into a problem first of all with a non-booting system after running #yum update centos-release It took me to 3.8 and upgraded all the other packages [b:7e931c835d]BUT[/b:7e931c835d] because of some stupid flags enabled in /etc/yum.conf the KERNEL WASN'T UPGRADED SO AFTER BOOTING, WELL IT DIDN'T BOOT OF COURSE :) H........
  • MySQL Server wouldn't start


    MySQL Server wouldn't startStart MySQL Server with the following script that would have installed with the port. /usr/local/etc/rc.d/mysql-server.sh start........
  • MySQL SubQuery


    MySQL SubQueryI was trying to do a sub-query here but it wouldn't work (Syntax Error) in MySQL for some reason even though based on the SQL standards it should be ok. [i:1268bfa39e][b:1268bfa39e]I found the reason this doesn't work. I am using MySQL 3.23 and I read on the MySQL web site that versions before 4.1 DO NOT SUPPORT SUB-QUERIES so it showed me how to rewrite the following as a LEFT join instead of a sub-query. [/b:1268bfa39e][/i:1268bfa39e]........
  • Enable/Disable PHP Warnings/Logs and Errors from .htaccess with Apache


    Put what you see below into your .htaccessand it will enable errors and notices. (change on to off and 1 to 0 to disable though) php_flag display_startup_errors on php_flag display_errors on php_flag html_errors on Now you'll be able to see errors and notices but this should really only be used for debugging purposes and only temporarily as it can be a security issue since errors can reveal information you wouldn't want hacker........
  • Hard Drive Not Working/Not Detected By Your BIOS Anymore?


    I was starting to panic because suddenly my 1TB Seagate SATA drive wasn't working,I thought it was a BIOS issue because it seemed to have happened after I tried overclocking my Desktop too much. I tried powering down and waiting, but I still couldn't hear the drive spin up at all. I tried a second 1TB hard drive and it wouldn't work either. I checked all power connections again and again until one of the pins in the MOLEX connector popped completely loose. Th........
  • Why Apple should thank the jailbreakers and not patch/stop the jailbreaking exploits


    First of all, the iPhone is crippled in many ways, but most of my complaints about functionality have been addressed through the jailbreak, Ican run apps in the background of my choosing, I can install a terminal, acccess my phone through SSH and SCP and so much more. It even addresses the 15 minute e-mail problem, I installed a program called "PushMod" and now set the checking time to just 1 minute. Apple should really thank the developers for this gift, it ma........
  • iPhone 3GS Jailbreak Information & Benefits


    Truly, the only way to unleash the capabilities and customization abilities of iPhone are to jailbreak, it's not just for hackers anymore. A few days ago someone by the named of "geohot" released a single click application called "purplera1n", which does the entire operation smoothly and seamlessly. In our case, the first time it went as far as "done, wait for reboot" on our Windows machine and for minutes we waited and saw the pic on the iPhone w........
  • SIOCSIFADDR No such device eth0 error while getting interface flags - eth0 Ethernet Device can


    Igot this after copying a VMWare image onto another machine in Debian. SIOCSIFADDR No such device eth0 error while getting interface flags The solution 1.) Find and edit the device line in persisent-net.rules note it will be prefixed with something like z25 or something else. vi /etc/udev/rules.d/z25_persistent-net.rules The easiest way is to comment anything out. If you are feeling........
  • BIND/NAMED woes


    Feb 5 01:39:33 server named[19768]: zone myzone.com/IN: serial number (12331465) received from master 127.0.0.2#53 < ours (200901281) The above is taken from /var/log/messages This can be annoying, it can happen for a variety of reasons. What seems to be happening here is that the slave realizes the time on the slave is ahead of the master, so it therefore assumes it has the most up to date copy and won't actually transfer the zone. The solutio........
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