• Linux partprobe/partx cannot access last and 4th partition


    On a test machine Iwas never able to access to a newly created 4th partiton. As we can see there are dev devices for everything but the 4th partition. The normal "partprobe" or "kpartx" or kernel being told to rescan the block device didn't help (only a reboot did). fdisk -l /dev/sda Disk /dev/sda: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders Units........
  • VMWare ESXi 6.7 SSH/PowerShell CLI Commands


    [root@localhost:~] BootModuleConfig.sh echo host-ind nfcd........
  • possible SYN flooding on ctid 42131, port 80. Sending cookies. - Solution


    The Linux Kernel interpretated a very high volume of real traffic as a DDOS attack so it basically ends up blocking your web server. possible SYN flooding on ctid 42131, port 80. Sending cookies. Simple fix edit sysctl values for max_syn_backlog sysctl -w net.ipv4.tcp_max_syn_backlog=5000 To make them permanent edit /etc/sysctl.conf echo "net.ipv4.tcp_........
  • ffmpeg Linux Mint download, compile and install howto


    #if you have nvidia make sure you install the nvidia-cuda-toolkit so hardware acceleration can be used wget http://ffmpeg.org/releases/ffmpeg-3.3.2.tar.bz2 tar -jxvf ffmpeg-3.3.2.tar.bz2 cd ffmpeg-3.3.2/ ./configure --disable-yasm install prefix /usr/local source path ........
  • remove gpt partition linux


    sudo fdisk /dev/sdh WARNING: GPT (GUID Partition Table) detected on '/dev/sdh'! The util fdisk doesn't support GPT. Use GNU Parted. WARNING: The size of this disk is 8.0 TB (8001563221504 bytes). DOS partition table format can not be used on drives for volumes larger than (2199023255040 bytes) for 512-byte sectors. Use parted(1) and GUID partition table format (GPT). The device presents a l........
  • 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........
  • /usr/libexec/mysqld: The table 'session' is full solution


    First of all if you're getting this error it is a result of extreme database activity. If you aren't expecting it or it doesn't make sense to you 99% of the time this is a database driven script being exploited (some common examples I see often are things like phpBB being hit by dozens, hundreds or thousands of bots making constant DB write requests). The easiest way to identify this is to restart MySQL and then run the third party tool "mtop" and you'll see all........
  • nf_conntrack: table full, dropping packet solution


    nf_conntrack: table full, dropping packet The above in some cases I've seen is a sign of a DOS attack or can occur if users are using services like torrenting, proxy, VPNetc... Do not take it lightly as the above can knock a server offline if the table becomes full and I've also seen full crashes and kernel panics shortly after. ........
  • LSI MegaRAID Adventures, Guide and HowTo


    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........
  • Bash weird variable whitespace missing when echoing printing


    Bash weird variable whitespace missing var=`cat tlds.csv|grep .ca,` # echo "var=:$var:" :ar=:.ca,Canada Why is the v missing in the last line? It should be :var=:.ca,Canada instead of :ar=:.ca,Canada I noticed a problem with the file with doing a "cat -v" on it. Here's the issue, the file contains carat M ^M: .vg,British Virgin Island........
  • Asterisk DOS attack - failed for '173.242.117.192' - Peer is not supposed to register [May 23 15:46:07] ERROR[32748]: chan_sip.c:13158 register_verify: Peer '153' is trying to register, but not configured as host=dynamic


    This happened to a customer Asterisk server and it somehow found the ID of the registration account to the upstream SIP server and was railing connection attempts (it filled up the console and there were literally thousands per second). Basically this caused all incoming and outgoing calls to fail. It was a temporary fix but the solution was to block that specific IP, it's hard to stop it 100% because the customer needs the default SIP port.........
  • 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........
  • mdadm: /dev/sdb1 not large enough to join array solution


    mdadm --manage /dev/md1 --add /dev/sdb1 mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. mdadm: metadata format 00.90 unknown, ignored. mdadm: /dev/sdb1 not large enough to join array md1's first primary member /dev/sda3 has 57394 cylinders while the /dev/sdb1 has 57393 (1 less cylinder) which is why it won't work. fdisk -l /dev/sda3 Disk /dev/sda3: 47........
  • How to mount/access a single partition from dd image with Linux


    parted sdc.img GNU Parted 1.8.8 Using /home/one/sdc.img Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) unit&nb........
  • convert carat ^M/M Windows based text files to Linux


    carat M isn't this symbol ^ that you think, it can only be produced by typing "Ctrl-v, Ctrl-m". That you might see in text files saved from Windows. tofrodos is the package that has dos2unix which is basically the same scripts that replace ^M with /n tofrodos is the Debian/Buntu package name which has the dos2unix and unix2dos binaries........
  • named/bind cannot find zone file, load zone files without specifying full directory path/loading master file genuine.com.zone: file not found


    genuine.com/IN: loading master file genuine.com.zone: file not found _default/genuine.com/IN: file not found I always found it silly that no one really talks about this and apparently many like me and even control panels like Plesk were still using hard paths. I always thought "why can't I just specify the name of the zone file and have bind find it". Surely the default search path must be /var/named or somewhere else but there is no such thing.........
  • WD EARS/Green 2TB Cannot Disable Power Saving/Head Parking with hdparm


    hdparm -B 255 /dev/sdb /dev/sdb: setting Advanced Power Management level to disabled HDIO_DRIVE_CMD failed: Input/output error The one thing you can do though is to set hdparm spindown time lower (it doesn't seem to work that well). -S set standby (spindown) timeout hdparm -S 251 /dev/sda /dev/sda: setti........
  • 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........
  • How to compile in Windows/DOS


    How to compile in Windows/DOSMingW is a free compiler project so start here: http://www.mingw.org/download.shtml#hdr2 I downloaded the core GCC compiler: http://prdownloads.sf.net/mingw/gcc-core-3.4.2-20040916-1.tar.gz?download But it's missing even the standard C runtime libraries like "stdio.h"! You may also need to add environment variables from the DOS command line. Here is a simpl........
  • Great FreeBSD Security DOS tutorial


    Great FreeBSD Security DOS tutorialhttp://www.onlamp.com/pub/a/bsd/2004/06/24/anti_dos.html........
  • [error] server reached MaxClients setting, consider raising the MaxClients setting - Apache


    Have you ever seen this dreaded message in your Apache/HTTPD /var/log/httpd/error_log? [error] server reached MaxClients setting, consider raising the MaxClients setting The error itself is slightly misleading. Ibelieve this happened to one of my servers, I found Apache was running still, and that you could telnet to port 80 but no respnose would be given. For some reason my error log initially did not have the above error, but after a restart I saw........
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