How to verify, if cable is connected to the interface in Linux? How to verify physical connection to network on interface in Linux?
If you are away from the server and unable to see if ethernet cable is connected to the particular interface in server, but you have another connection (i.e.: via iLO Console), you can use ethtool to verify physical connectivity on that interface remotely.
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Typical OpenStack cloud setup consists of more than one node (usually one Controller node and several Compute nodes), which requires lot of physical computers / servers available to perform the installation. This complicates the situation, especially if we need to test OpenStack on many nodes. Fortunately we can use Linux KVM (Kernel-based Virtual Machine) to create OpenStack on virtual nodes and avoid problems with obtaining physical hardware.
In this tutorial we will show you how to install OpenStack on KVM on Fedora 21 based hypervisor. We will run Openstack installation on two KVM based virtual nodes (Controller and Compute).
The most important part in configuring KVM for OpenStack installation is network setup, we also need to secure some resources (VCPUs, RAM, disk space) on KVM Hypervisor to create two virtual nodes.
SELinux (Security Enhanced Linux) is an additional method of Linux system protection. It’s a group of security contexts that determine which process can access which files, directories, ports, etc…
SELinux has three modes:
Enforcing: SELinux protects files, directories, ports against unauthorized access and logs all SELinux events and attempts.
Permissive: SELinux allows all interactions and context violations and logs them. Permissive mode is often used for troubleshooting SELinux.
Disabled: SELinux is completely disabled.
SELinux in Enforcing mode may cause problems accessing files or ports in the system, that’s why it’s good to know how to change it’s mode or even disable it.
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You can compare two text files in Linux using the following command-line tools:
– diff
– vim / vimdiff
These tools are already installed “out-of-the-box” in most Linux distributions.
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Secure Shell (SSH), besides standard password authentication, gives us the possibility to authenticate using private – public key relation. This allows us access remote systems without typing the password each time we want to connect and the connection is still secure. This method is based on generation of two keys: private key (kept private on our local host), public key (given to any remote host we want to connect to passwordless).
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DHCP (Dynamic Host Configuration Protocol) is a network protocol used for dynamically assigning IP addresses for computers attached to the network. Standard port used for DHCP service: 67(UDP).
In this tutorial we will launch dhcp server on CentOS 7 / RHEL 7 and define example subnets.
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