• How to kill a docker swarm


    Assign way more replicas than you have of memory on all nodes and watch the Swarm crash which can easily reproduce in a small VMfor testing. root@Deb11Docker01:~# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAM........
  • isc-dhcp-server dhcpd how to get longer lease


    You can do a static lease that is tied to the MAC address but what a lot of users prefer is that they come into the office or lab the next day and that their device gets assigned the same IP address (if possible). As we can see in the dhcpd logs that there is threshold that is defaulted as we'll show later. Whatever the threshold is set at, if the lease is younger than the threshold, it will keep the same lease. In other words, if the device goes to sleep or is powered off........
  • Virtualbox Best Networking Mode In Lab/Work Environment without using NAT Network or Bridged


    Virtualbox is a very powerful tool, but for some use cases it is less than optimal. Say you are in a work, lab or other environment where you are not alone on the physical network and there could be overlap of IPs, but you need all of your VMs to be contactable from your host, VMs need to communicate with each other, and VMs need internet. NAT Network will give you VM to VM communication and internet, however, it is buggy and unstable. It also doesn't allow host to VM co........
  • Linux grub not using UUID for the root device instead it uses /dev/sda1 or other device name solution


    You can read lots of posts about this issue but there is not much information about why this is the case or how grub determines the root= device name. Some even suggest modifying grub.cfg manually which is a disaster as the next kernel update will cause grub to revert back to the device name. For most people this won't be an issue but those using template system, automated deployments and working in embedded may run into this issue with custom embedded and created minimal kernel........
  • Generic IP Camera LAN Default IP Settings DVR


    If you are converting a generic wifi IP camera to ethernet, it may not be that simple as many are default hard coded to a static IP of 192.168.1.168 and login info admin/admin. From there you can login to the camera and assign it to DHCP by going to http://192.168.1.168 For security these cameras +DVR should be on a separate untagged VLAN or if possible a physically isolated non-internet connected switch/network. The reference below is applicable to many of the r........
  • How To Do Linux Network Bonding Teaming in Mint Debian Ubuntu


    Bonding is an excellent way to get both increased redundancy and throughput. It is similar to the "Network Teaming" feature in Windows. There are a few different modes but we will use mode 6, I think it's the best of both worlds, as it is not just a failover, but it provides round robin, so you will get redundancy and load balancing. So if you have a 1G single port, you will have a combined throughput of 4G at this point. Just bear in mind that the true thr........
  • Docker Tutorial HowTo Install Docker, Use and Create Docker Container Images Clustering Swarm Mode Monitoring Service Hosting Provider


    The Best Docker Tutorial for Beginners We quickly explain the basic Docker concepts and show you how to do the most common tasks from starting your first container, to making custom images, a Docker Swarm Cluster Tutorial, docker compose and Docker buildfiles.........
  • VirtualBox VBox Nat Network Handing Out Wrong IP Address Subnet Solution


    This seems to be an ongoing issue that is still reproducable in the latest Ubuntu Vbox 6.x. The default NAT Network range is usually 10.0.2.0/24. If you change this range it does not seem to work properly. Say we change the range to 10.50.1.0/24 If you get a new lease you will find that you get an IP from the old range but the default gateway is from the new range. ........
  • Juniper JunOS Command Overview and Howtos Switch, Router, Firewall Tutorial Guide


    Enable "cli" mode equivalent in JunOS cli Configure Mode configure So rather than going to the console on a Cisco switch and typing "enable" and then "conf t", the equivalent in JunOS is "cli" and "configure". How Do You Apply Changes You've Made? You can make all kinds of changes to the switch, but remember they are not........
  • Virtualbox Error Cannot register the hard disk because a hard disk with UUID already exists solution


    Cannot register the hard disk '/some/path/windows-marking.vdi' {f54def00-2252-43f5-9178-0998636cad61} because a hard disk '/other-path/windows-marking.vdi' with UUID {f54def00-2252-43f5-9178-0998636cad61} already exists. Result Code: NS_ERROR_INVALID_ARG (0x80070057) Component: VirtualBoxWrap Interface: IVirtualBox {0169423f-46b4-cde9-91af-1e9d5b6cd945} Callee RC: VBOX_E_OBJECT_NOT_FOUND (0x80BB0001)........
  • Nvidia Ubuntu Linux Screentearing Video with solution driver


    This seems to happen on most if not all Nvidia cards but the good news is that if you are using any of the Linux drivers and have the nvidia-settings tool installed it is just a simple command. Solution: nvidia-settings --assign CurrentMetaMode="nvidia-auto-select +0+0 { ForceFullCompositionPipeline = On }" Enter the above command in your terminal and the screentearing will be fixed which is like enabling Tear Free on AMD cards.&........
  • Howto Set Static IP on boot in initramfs for dropbear or other purposes NFS, Linux, Debian, Ubuntu, CentOS


    This is only really necessary in the case you don't want DHCP. If you are dealing with an encrypted LUKS server on the internet, you will often want to have a static IP so you know which IP to connect to (or if you have a semi-static IP assigned by DHCP). SET IP Address by /etc/initramfs-tools/initramfs.conf IP Address=192.168.1.27 Gateway=192.168.1.1 Subnet Mask: 255.255.255.0 Hostname=myhome.com IP=192.1........
  • Cisco Unified Communications Manager Express Cheatsheet CUCME CME Tutorial Guide


    Video Links: How To Setup 2 Phones on a Single CME Router and get the GUI going. How to use Dialpeers with CME with two routers How to implement call restrictions using COR / Class of Restriction Getting started, let's enable ephones and DNs we can add a phone with........
  • bash if statement how to test program output without assigning to variable


    A common method in bash is to assign output to a variable like this: somevar=`uptime` That works too but it could be more efficient to do something like this: if [[ $(uptime|awk '{print $3}') > 20 ]]; then echo "uptime greater than 20 days"; fi........
  • RTNETLINK answers: Network is unreachable


    This often happens if you are adding a secondary route, especially with Linux source based routing. ip route add default via 10.10.10.254 table 10 RTNETLINK answers: Network is unreachable If that happens you will probably find that it is unreachable because your NIC does not have an IP in the 10.10.10.0/24 range so just assign an IP in that range to your NIC and try again. eg. ifconfig eth0 10.10.10.254 netmask 255.255.255.0 up........
  • Cisco Unified Communications Manager / CUCM IP Telephony Definitions


    DN = Directory Number: It is basically the extension of the phone In the example below, 55 is a DN assigned to the phone.........
  • Cisco Router Setup Guide and Tutorial Howto With Commands and Examples


    In most of the Cisco router IOS I find the ports like ge0/0 ge0/1 and ge0/2 or whatever your ports are down. They will not even give you a link light. So one of the first tasks should be getting the port you are working with up. In my case the first goal is often connectivity with the LAN and WAN. LAN = your local area network (eg. in the office/home ) WAN= your ISP/public internet (eg. fiber/cable/dsl/ethernet).........
  • Cisco Switch Setup Guide Command List


    Enter configuration console: enable configure terminal This is important because if your console doesn't look like below none of the commands will work! Switch(config)# Save and Apply Settings wr Show Switch Configuration: show run Show Port List/Sta........
  • SSH error cannot Forward or Listen "bind: Cannot assign requested address"


    debug1: Local connections to LOCALHOST:18006 forwarded to remote address 192.168.1.93:8006 debug1: Local forwarding listening on 127.0.0.1 port 18006. debug1: channel 0: new [port listener] debug1: Local forwarding listening on ::1 port 18006. bind: Cannot assign requested address What we are seeing is that we can't listen on an IPV6 address of ::1. We need to tell SSH to stop using IPV6 so we'll edit ssh_config to take care of this issue........
  • VMWare Pro Workstation Nic Disconnected and No IP Using NAT


    By default VMWare Workstation often doesn't work as we would like. If you create a VM with a default NAT IP it won't work you will find the NIC is disconnected (even though on the VMWare side it says connected including at Power On). How To Solve It 1.) Create New VMNet for NAT Click "Edit" -> "Virtual Network Editor" Click "Add Network" Select Network To Add "VMNet1" (........
  • Linux Kernel USB Export Errors


    4.374647] usb_common: exports duplicate symbol usb_get_dr_mode (owned by kernel) [ 4.403334] usbcore: exports duplicate symbol __usb_get_extra_descriptor (owned by kernel) [ 4.427736] xhci_hcd 0000:00:15.0: xHCI Host Controller [ 4.427844] xhci_hcd 0000:00:15.0: new USB bus registered, assigned bus number 1 [ 4.429040] xhci_hcd 0000:00:15.0: hcc params 0x200077c1 hci version 0x100 quirks 0x01109810 [ 4.429141] xhci_hcd 0000:00:15.0: cache line size of 64 is not sup........
  • Linux Mint 18 Screen Goes Dark or Black After Screensaver or even when using the Desktop Solution


    You can search for this bug and it seems like it may be related to ecryptfs and is many years old. The symptoms are that you return to the computer and the screensaver was active or the screen was asleep/black and it doesn't seem to come back. But you check by SSH the computer is running fine and are frustrated you'll lose your running programs and have to reboot. There is a simple solution: Ctrl + Alt + F1 Ctrl +Alt + F8 Ba........
  • samba how to listen on specific IP only


    This is useful for security purposes especially on a server which may have a public IP assigned to it but has a second NIC for the LAN. Here is how you edit smb.conf: [global] interfaces = 192.168.1.50 bind interfaces only = yes As you can see above it will only listen on 192.168.1.50 and remind to keep the "bind interfaces only"option.........
  • Nvidia Linux Mint/Ubuntu screentearing horizontal line solution


    Finally after ages I found the solution which is on many pages on the net but not obvious and should have been standard or more common info! Instant Solution: Type this into the terminal (unfortunately the driver config menu doesn't have the option as itis hidden): nvidia-settings --assign CurrentMetaMode="nvidia-auto-select +0+0 { ForceCompositionPipeline = On }" Make permanent Cli........
  • Nvidia Linux Card not working due to LSI 9200/SAS2008 IRQ conflict


    At first my BIOS said the card may not work right because there is no more option ROM space. I disabled the Option ROM for both LSI 1068 and 2008 chipsets, Network Boot ROM and most other PCI slots, Serial Port, etc... and the message went away but the card still does not work properly. But it still cannot initialize the card properly(does not work): [ 33.943272] NVRM: This PCI I/O region assigned to your NVIDIA device is invalid:........
  • How to install grub on virtio KVM with Linux


    I messed up the bootloader by accident on a standard Centos 6.3 install because I turned the /dev/vda1 boot partition into an mdadm raid 1. This was all done correctly aside from one point Ididn't realize was an issue metadata=00.90 is the only thing that will allow you to boot (otherwise grub won't work and you won't boot). So the next step is rescue mode from a CD right? The problem you will find is that grub does not detect your hard drives, this is Ibelieve is be........
  • Dell CS24-NV7 Howto Enable LAN/NICs and PXEBoot in the BIOS


    Dell CS24-NV7 Unusually the Virtualization was enabled when I got this server but all the NICs were diabled in the BIOS including PXE boot! Advanced -> Advanced Chipset Control PCI Slot 1 Option ROM: Enabled Onboard LAN1 Control: Enabled LAN1 Option ROM Scan: Enabled (you need it for PXE boot) Onboard LAN2 Control: Enabled LAN2 Option ROM Scan: Enabled *you will need to reboot and........
  • Apache SNI is not needed what is the issue?


    Iread this article and still don't understand the issue. If I understand correctly the client negotiates after the first SSLconnection and then gets the correct hostname and thus correct certificate. http://wiki.apache.org/httpd/NameBasedSSLVHostsWithSNI To their credit I know I'm not using SNIbecuase Iget this message in the Apache log :) [warn] Init: You should not use name-based virtual hosts in conjunction with SSL!! B........
  • PHP Security - Enable Safe Mode to increase security


    Everyone should be running with safe_mode on in /etc/php.ini (on Centos) as it makes exploiting your system more difficult is PHPcan't execute anything on the system if a script is exploited. For example with Safe_Mode on the only executable files on the system are ones in the safe_mode_exec_dir = /safephp This is crucial, if you must execute anything from PHPthen you have to copy the binary and assign to the user that Apache runs your site under.&........
  • bash script howto use heredocand assign to a variable and write to a file


    zonetemplate=$(cat ........
  • PHP How To Create and Assign Variables from POST/Submit FORM


    foreach ($_POST as $key => $value) { if ( $key != submit ) { $values.="$key=$value<........
  • eth0 changed to eth1 or eth2 and the solution to fix it


    If you move your hard drive(s) around to other computers/servers, you'll find that your eth0 keeps getting higher, the first time it will become eth1 and then eth2 etc and even higher if your server has dual or quad NICs. The reason is that udevd basically assigns eth0 tot he first NIC it finds and remembers it, if it encounters a NIC with a differentMAC, it assigns it one higher (eg. eth1). See the example below, I have eth2 now so how doI fix it?........
  • xen how to resize an image properly


    The best way I could figure out is to use another guest of some sort to do this, while assigning the disk that needs to be resized to the same guest. So say we have /dev/xvda as the guests drive and we've booted it up. We also have /dev/xvdb (this is going to be the image/disk to be resized). In this case it's based on an ext3/4 image. Run e2fsck on it to ensure there are no filesystem errors. e2fsck /dev/xvdb........
  • 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........
  • Outsourced VPS Support


    The Xen VPSI had was not working properly and when they asked for the login information I found the support was coming directly from India: whois 122.178.148.* [Querying whois.apnic.net] [whois.apnic.net] % [whois.apnic.net node-5] % Whois data copyright terms http://www.apnic.net/db/dbcopyright.html inetnum: 122.178.128.0 - 122.178.191.255 netname:&........
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