• /etc/iproute2/rt_tables default settings file in Linux Centos 6,7 and most other NIX's


    This should apply to most Linux distributions just incase you get into trouble or wipe out the defaults by accident. /etc/iproute2/rt_tables # # reserved values # 255 local 254 main 253 default 0 unspec # # local # #1 inr.ruhep........
  • How to Update Linux /usr/share/misc/pci.ids


    This works with lspci and if it's outdated may not give you the exact manufacturer and device model. For example take these 3 different RX 580's: 1a:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Device 67df (rev e7) 1b:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Device 67df (rev e7) 1d:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Device 67df (rev e7) You ca........
  • yum how to install old obsolete packages


    This is important as unfortunately Centos may designate a package obsolete and the replacement breaks everything (eg. you have a config file and the new replacement is not at all compatible with it and it breaks your application). This is where disabling obsoletes comes into play, it can be done from yum but it doesn't work at the time I find. yum --setopt=obsoletes=0 install someapp However Ifind it still installs the new app and not the one you ask for........
  • How to verify SSL SHA-1 Certificate Fingerprnit Signature of your mail/web server to avoid hijacking/man-in-the-middle attacks


    This is especially helpful if you run your own servers. If you are presented with an error message or warning that the signature has changed or does not match the IP/domain you are connecting to you always want to verify manually. So your e-mail/web client will show you an SHA-1 fingerprint like this: "Could not verify this certificate because the issuer is unkown" or other reasons such as a mismatch in IP/domain. It will also show you........
  • mdadm frozen and doesn't realize array is dead/missing failed due to unplugged drives


    This was a surprising bug but I unplugged all drives for an array md127. At first it was just 1 drive and mdadm seemed to notice this. I unplugged the second drive taking the array offline but mdadm did not realize it was offline and still showed a non-existent disk as being part of it. This created problems trying to unmount it or even to stop this array with mdadm freezing. As for how to fix it I can only think of making sure you are not in a mounted path of........
  • Linux CLI command to rip audio CD and encode convert to MP3s


    This command rips the audio tracks to .wav files *I recommend making a new directory with the name of the audio disc first and executing everything from within that directory below. cdparanoia -B Use the lame mp3 encoder to encode each one with this script: *Note that this will encode any other files ending in "cdda.wav" for track in `ls *cdda.wav`; do lame -b 192 $track; done........
  • mdadm how to add additional RAID 1 drives


    This is a great way to upgrade your RAID array or move it/copy it to a new set of hard drives. Eg. you have a current RAID 1 array on older/slower drives. Just add at least 1 of the new drives to the array, update grub/install it and then boot into it. Then you have a transparent data migration that is fully synchronized. mdadm --grow /dev/md126 --raid-devices 3 md127 : active raid1 sdc1........
  • MySQL HowTo Copy Duplicate a Table for backup purposes


    This is a great way to test and experiment without risking your current table, or to make a backup of your current table to avoid corruption or dataloss due to malicious activity eg. deletion etc.. There are two steps and two commands 1.)Copy Table Structure "cars_backup" is the new table and it will be a copy of the table called "cars"........
  • WD 20EARX 2TB Bad within days


    This is just trying to read 5GB off the drive with dd and the drive initially tested ok but shortly after I wondered why I was seeing 2MB/s read speeds. Notice the "current_pending_sector", anytime I've seen it at anything above 0 even with no other bad fields/attributes, it means the drive is bad. ata1.00: exception Emask 0x0 SAct 0x3 SErr 0x0 action 0x0 ata1.00: irq_stat 0x40000008 ata1.00: failed command: READ FPDMA QUEUED ata1.00: cmd 60/00:00:........
  • How to wipe/erase hard drives clean so data cannot be recovered for privacy reasons


    This is something many people and especially businesses worry about, or at least they should. Before throwing away a hard drive, returning a hard drive, or especially Warrantying/RMAing it, you should wipe the drive. Linux provides the "shred" and "dd" utlities which work quite well. It seems even a single pass is good enough but by default shred will do 3 passes. Here's an example of using shred in Linux (I use a custom made distribution from........
  • Directadmin Log File Locations


    This is a handy link and list of all the relevant Directadmin log files and related servers. http://help.directadmin.com/item.php?id=11 DirectAdmin: /var/log/directadmin/error.log /var/log/directadmin/errortaskq.log /var/log/directadmin/system.log /var/log/directadmin/security.log Apache:........
  • How to recover from dead DRBD partition/hard drive in two simple commands


    This assumes that you've at least created the correct partition for your DRBD already. Notice that I am "diskless", that's because either your DRBD partition doesn't exist/has been renamed (eg. sdb becomes sda when sdb dies and you reboot) or because that drive is really actually dead/gone. *If you need to permanently change the partition/device for your resource be sure to edit /etc/drbd.conf on both hosts and reload the config. (replace r0 with........
  • exim high load and dozens of processes


    This server was experiencing loads of up to 80 and maxing out the RAM and kmemsize on a CPanel VPS. There were literally dozens if not hundreds of exim processes. I have no idea why exim has such a design that would allow it to consume this much CPU and RAM. Any normal MTA should not be spawning so many processes, it should be processing them in sequence and if it is going to spawn hundreds of processes in response to a large volume of mail, it's better to have a delayed del........
  • Canel Default VHOST DocumentRoot/Contents Directory is /usr/local/apache/htdocs


    This can be very annoying and CPanel doesn't seem to document it, or it's not found or made as obvious as it should be. It's always funny when I find it more difficult to work with a control panel than to do everytihng manually without CPanel or even Plesk. So once again, the default serve path for contents is: /usr/local/apache/htdocs and this is especially applicable when accessing Apache by just an IP which is unbound to any domain at this point.........
  • 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........
  • Adventures in pre-paid SIM Cards and data GPRS/Edge/3G in China with China Mobile in Shenzhen, Guangzhou, Shanghai, Beijing and other cities


    This really is a difficult and confusing process for non-Mandarin speakers, but here's what I've done and learned so far: You can purchase an "M-Zone" China Mobile pre-paid SIMCard from almost anywhere but I tried to purchase mine from Suning (a large electronics dealer) hoping they would be able to help me or answer my questions but my plan didn't work out at all. At Suning once I found someone who spoke some English they gave me the 55 RMB M-Zone China Mobile P........
  • RTL8111/8168B R8169 Gigabit Link slow speeds


    This is the Intel Atom 330 motherboard with integrated Realtek Gigabit NIC (Intel Desktop Board D945GCLF2 Motherboard W/ Atom 330 1.6 GHz Dual Core Processor - Mini-ITX) I cannot achieve more than 15 MB/s, even doing a local transfer through eth0 to it's own IP. 100% 95MB 15.9MB/s 00:06 So this is not a cabling, switch or hardware issue, it seems like a driver or chipset limitation problem. Here is my........
  • LAME MP3 Encoder Segmentation Faults


    This happened on one of my Ubuntu machines where Igot some kind of segfault on line 21 from LAME at random while encoding MP3s (a second try is fine usually). I've read that it's best to compile it from source and that has solved most issues for people. Here is my preferred configure line: ./configure --enable-mp3x --with-fileio=lame --enable-debug --with-vorbis Even with that I got a different error this tim........
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