• CentOS 6 and 7 / RHEL Persistent DHCP Solution


    It is very silly but the default on the ifup-eth script tells dhclient ( the program that obtains a DHCP IPaddress if you have selected DHCPin your ifcfg-eth* config file) to EXIT / QUIT if the first attempt to obtain a lease fails. No amount of dhclient.conf settings will fix this because if dhclient is started with -1 (which it is by default)then dhclient will quit. This is obviously very bad for MOST cases. Say for example you have a power outage or........
  • VBOX VirtualBox How To Import Raw .img Disk File


    What you need to do if you have taken a dd or real raw image dump of a hard disk: VBoxManage convertdd windows2019-eval-template.img windows2019.vdi --format VDI The .img is the raw dd dump and the .vdi is the output file. --format VDIspecifies to output to .vdi format If you are in a pinch you can always use qemu-kvm binary and manually specify the .img as your disk and i........
  • Centos 7 Reallocate logical volume space to another


    Do you hate how Centos 7 defaults to allocating most of your valuable space to /home even though it is a production server? Here is a quick guide on how to take back that space live, while online (of course make sure you have backups just in case something goes wrong!): First we will reduce our home dir by 100G: lvreduce -L -100G /dev/mapper/centos-home WARNING: Reducing active and open logical volume to ........
  • Linux How To Create A RamDisk


    size = the amount of RAM (m for megabytes) /mnt/ram = the mount location of the ram disk (change to the path you want it mounted to) mount -t tmpfs -o size=4096m tmpfs /mnt/ram/ Example test in an old server: You can see that when reading if you don't specify bs1=M the read speeds are several times slower (eg. 450MB/s vs 2.1GB/s) mount -t tmpfs -o size=4096m tmpfs /mnt/ram/^C root@testserver:~# dd........
  • systemd management using systemctl and journalctl to check systemd logs


    systemd is like the service manager for your Centos and other modern Linux distributions (including Debian/Mint/Ubuntu) allows you to enable services, stop them, restart them, check their status and even reboot your system. The key commands or arguments you will use with systemctl are the following: Unit Commands: list-units [PATTERN...] List loaded units &nbs........
  • Proxmox error uploading an iso solution


    Error 0 occurred while receiving the document root@vh1:/var/tmp# wget http://mirror.compevo.com/proxmox/proxmox-ve_5.2-1.iso --2018-08-30 16:27:37-- http://mirror.compevo.com/proxmox/proxmox-ve_5.2-1.iso Resolving mirror.compevo.com (mirror.compevo.com)... 103.25.61.44 Connecting to mirror.compevo.com (mirror.compevo.com)|103.25.61.44|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 641517568 (612M) [application/o........
  • GCC 5 on Centos 6 - How To Install


    Install requirements: yum -y install gmp-devel mpfr-devel libmpc-devel glibc-devel glibc-devel.i686 zip unzip jar Download, untar, configure, compile and install GCC http://mirrors.kernel.org/gnu/gcc/gcc-5.5.0/gcc-5.5.0.tar.gz tar -zxvf gcc-5.5.0.tar.gz cd gcc-5.5.0 ./configure make make install Now you need to cleanup th........
  • Migrate Centos 7 from Single HDD to mdadm RAID 10 array:


    Done on Centos 7.3 very important as clearly based on older guides it was a lot easier and more simpler! Hint do not use grub2-install! One huge caveat if you are an oldschool user or sysadmin who has avoided UEFIbooting The normal way will not work here if your Centos was using UEFI. Newer systems use it by default. The easiest way to check is to do an fdisk -l if your sy........
  • php read file into variable


    php read file into variable $content = file_get_contents(home.html); Otherwise if you want to get the source code of the PHP file, it's the same as a .txt file: $content = file_get_contents('/path/to/phpfile.php'); You can also get from URLs: $content = file_get_contents('http://someurl.com/file.txt');........
  • OpenVZ Solution CPT ERR: c02fa000,73 :CPT: lock fd is closed incorrectly: 1 and vps-net_add ERROR: Unable to add route ip route add 192.168.5.2 dev venet0


    The only solution after trying many suggestions was to simply restart the "vz" service (definitely not preferable). Even doing an ifdown and ifup for venet0 did not help. ifup venet0 Bringing up interface venet0: Configuring interface venet0: net.ipv4.conf.venet0.send_redirects = 0 RTNETLINK answers: Network is down Some errors from log: CPT ERR: d2dc60........
  • Centos 6 how to guide convert LVM non-RAID into mdadm 1/10 RAID array live without reinstalling


    Here is the scenario you or a client have a remote machine that was installed as a standard/default minimal Centos 6.x machine on a single disk with LVM for whatever reason. Often many people do not know how to install it to a RAID array so it is common to have this problem and why reinstall if you don't need to? In some cases on a remote system you can't easily reinstall without physical or KVM access. So in this case you add a second physical or disk or already ha........
  • ONVIF Linux Security Camera Setup


    First of all this seems to apply to many ONVIF devices Hard coded IP: 192.168.1.10 (yes not kidding no DHCP!) 00:12:12:9C:C2:00 To view RTSP stream use VLC, or openRTSP or other RTSP capable software: rtsp://192.168.1.10/user=admin_password=tlJwpbo6_channel=1_stream=0.sdp user: admin password: blank http://ip/Login.htm Uses Quicktime and is a poor quality picture and slow Cannot change pass........
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    It is a permissions issue that is hard to fix. All but one USB device is greyed out. I am already a member of "vboxusers" I have already enabled and disabled USB support for the guest. I have already reinstalled the latest VBOx guest editions If running as root it all works fine Changing........
  • Samsung Printer Password Login to change settings CLP


    First of all to find your IP you can hold the "X" button for a few seconds and it will print out the DHCP IP. Another way to find the IP that I prefer is to login to your router or switch and find a hostname that says something like "SEC001599CD2948" which will be your Samsung printer (at least for the C3xx or C4xx series of Samsung printers). The login and password for Samsung Syncthru Webservice:........
  • CPanel Link to all of the command line options


    CPanel says you can access 98% of the functions through CLI which experienced Unix/Linux admins prefer for simplicity and for scripting.  I've never found CPanel easy to use from the admin panel, it seems everything is hard to find and a simple task becomes a series of hunts. So for people like me here's the list: http://cpanel.net/system-administrators/command-line-scrip........
  • drbd won't create device if previous partition is on it Command 'drbdmeta 0 v08 /dev/md160 internal create-md' terminated with exit code 40


    This is what fixed it: [root@box13 ~]# dd if=/dev/zero of=/dev/md160 bs=512 count=500 Basically you need to wipe out more than just the 512 byte partition table so 512 bytes * 500 is more than enough to make DRBD happy and think the partition is now empty. The reason this happens is because it gets confused when there is a previous partition with data on the device you are using. root@box13 ~]# d........
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    One thing to remember is that you need MegaCli to do the flashing. You also need the correct file,I tried at least 2 different Perc 6 firmwares from Dell that kept getting rejected as corrupt by MegaCli(they were really the wrong version). I have an external PCI-E Dell 6 Perc/I butI chose images from the 'Integrated" on motherboard version as it was allI could find. They are different, and below is my first time finding success.........
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    I flashed an LSI Logic firmware to it and it broke the BIOS (cannot do Ctrl+R) for booting purposes but allows other functionality to work normally. I tried downgrading to a Dell firmware for Perc 6i but it won't work, not even with MegaCli wget http://downloads.dell.com/FOLDER00416606M/1/SAS-RAID_Firmware_W83M2_LN32_6.3.1-0003_A14.BIN --2013-08-26 12:53:39-- http://downloads.dell.com/FOLDER00416606M/1/SAS-RAID_Firmware_W83M2_LN32_6.3.1-0003_A14.BIN Resolvi........
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    LSi Megaraid At first it was configured as a RAID 0, then I deleted the Virtual Disk Group. I thought both drives would be shown and detected in Linux as sda and sdb but it actually shows nothing. To make them work you have to hit Ctrl+R before the system boots (when prompted) and create a Virtual Disk Group. In my case I created each one as RAID 0 (with a single drive only) as I just wanted JBOD but there is no such option or default in these Dell Pe........
  • Country List Names in HTML Select From


    This is useful for developing a lot of applications, I'm putting it here to keep it handy for myself and hopefully others: Choose CountryCanadaJapanUnited StatesUnited KingdomAfghanistan........
  • lvm resize and use the remaining extra space


    df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg_12-lv_root 50G 1.2G 46G 3% / tmpfs 7.8G 0&nb........
  • Linux Out of Memory OOM Object Killer Solution "Out of memory: kill process 1955 (sshd) score 81 or a child"


    I had a system running a 128MB live CD image with 2.8 gigs of available RAM and the OOM kernel killer went crazy when using dd for more than 8 minutes and kept killing everything. I've read that this is due to a low-memory issue and paging in the kernel and 32-bit systems with lots of RAM. I even enabled swapspace on my LiveCD and the issue happened 25 minutes into dd rather than 8 minutes, so what gives? Also no swap space was ever used! cat /proc/s........
  • Linux High IOWAIT updatedb can't be killed and crash with mdadm


    high IO wait 424 root 39 19 1900 848 552 D 0.0 0.0 0:00.91 updatedb root 424 0.0 0.0 1900 848 ? DN Mar11 0:00 /usr/bin/updatedb -f sysfs?rootfs?bdev?proc?cpuset?binfmt_misc?debugfs?sockfs?usbfs?pipefs?anon_inodefs?futexfs?tmpfs?inotifyfs?eventp........
  • Linux - mptbase/MPT Fusion LSI Logic Error mptbase: ioc0: ERROR - didn't initialize properly! (-1)


    kernel 2.6.27.54 Fusion MPT base driver 3.04.07 Copyright (c) 1999-2008 LSI Corporation Fusion MPT SPI Host driver 3.04.07 mptbase: ioc0: Initiating bringup mptbase: ioc0: WARNING - Unexpected doorbell active! mptbase: ioc0: ERROR - Doorbell ACK timeout (count=4999), IntStatus=80000001! mptbase: ioc0: ERROR - Diagnostic reset FAILED! (102h) mptbase: ioc0: WARNING - NOT READY! mptbase: ioc0: ERROR - didn't initialize proper........
  • email server messsages rejected without reverse DNS DNS check failure Client host rejected: cannot find your reverse hostname Cannot resolve PTR record


    Basically you should always be 100% sure that whatever IPyour mail server sends out with has reverse DNS/PTR records. Remember that unless you own your IPs then you won't be able to set your own reverse DNS. Even if you were to create a reverse PTR record on your DNS servers it will be ignored. Reverse DNS is queried to pre-assigned DNS servers of your ISP, so therefore you'll need to contact your ISP/Colo/Hosting provider to do a reverse DNS entry. If you don't have........
  • 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........
  • FUSE/Curlftpfs mount ftp account as drive partition in Linux


    This is a great way to use your ftp server space, for example on your web hosting account (althoughI believe many hosts don't allow storage like this), but if you have a VPS/Dedicated Server etc.., this would be perfect. Imagine how easy it is to work with an ftp account that you can just mount as a normal partition or directory in Linux, it would be great for backups etc.. Name curlftpfs - mount a ftp host as a local directory Synopsis........
  • tar gzip: stdout: File too large - Error Size Limit on Large file > 17GB


    The folder I was trying to archive is about 72GB, but much like rsync at about 17GB it chokes because of the filesize. What's with so many common and essential Linux tools having such limitations? I guess it is likely that the authors never wrote their code with the idea that files would be so large but it's still very annoying. It's important to stay on top of these limitations on production servers because I didn't realize what happened until I checked the file with "........
  • Picking an FTPD (vsftpd) Server in Linux Centos/Debian


    I decided on using yum to help me decide even though I normaly use proftpd I decided to see what else I could find. yum search ftp Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * rpmforge: ftp-stud.fht-esslingen.de * base: mirrors.netdna.com * updates: updates.interworx.info * addons: yum.singlehop.com * extras: mirrors.netdna.com rpmforge........
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    ./ntfs-3g /dev/sda1 /mnt -o force Unexpected sectors per cluster value (127). Failed to mount '/dev/sda1': Invalid argument The device '/dev/sda1' doesn't seem to have a valid NTFS. Maybe the wrong device is used? Or the whole disk instead of a partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around? This is happening on a system I've come across an HP 6930P running Windows XP Professional. The partition appears to be very norm........
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    Here are the results, it is Sempron 3000+ AMD Mobile, 500Gig HDD, 512MB RAM with shared ATI Radeon graphics. # # # # # # # ##### ###### # # #### # # # # ## # # # #&nb........
  • PHP cannot access /usr/bin/openssl


    PHP cannot access /usr/bin/opensslI have verified the username that runs the process is able to access /usr/bin/openssl and it does exist but the PHP script is saying it doesn't exist: [code:1:1fd0f3abbe] if (!file_exists($OPENSSL)) { //echo "ERROR: OPENSSL $OPENSSL not foundn"; }[/code:1:1fd0f3abbe] I don't get itI can clearly see the contents of /usr/bin by using the PHP system fu........
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    Helpful IPFW ExamplesSomeone's real life examples: http://lists.freebsd.org/pipermail/freebsd-security/2004-July/002181.html Or you can try the FreeBSD Handbook guide: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/firewalls-ipfw.html........
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    CVSUp the Easy WayIf you're reading this you probably have never used CVSUp or don't know how. CVSUp can be used for two things or just one if you prefer. *Keeping your kernel up to date *Keeping your port list up to date Start by editing the following file in: [b:76928b387d]vi /usr/share/examples/cvsup/cvs-upfile[/b:76928b387d] It can be quite overwhelming with all the crazy options. Basically there are only 3........
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