The CGroup Subsystems in Red Hat Linux

The CGroup Subsystems in Red Hat Linux

Control groups (a.k.a. cgroups) allow you to allocate resources — such as CPU time, system memory, network bandwidth, or combinations of these resources — among user-defined groups of tasks (processes) running on a system. You can monitor the cgroups you configure, deny cgroups access [...]
Hyper: Hypervisor-based Containerization solution

Hyper: Hypervisor-based Containerization solution

Hyper does one thing: Provide isolated environments (virtual machines) on which portable environments (containers) can be easily scheduled. Hyper uses both shared and dedicated kernels environments, believing it is the right approach to deploy multi-tenant platforms.
Go 1.7 released

Go 1.7 released

The latest Go release, version 1.7, arrives six months after 1.6. Most of its changes are in the implementation of the toolchain, runtime, and libraries. As always, the release maintains the Go 1 promise of compatibility, which expects almost all Go programs to continue to compile and run as before.
Smart way to build an PPTP/L2TP VPN on CentOS 7

Smart way to build an PPTP/L2TP VPN on CentOS 7

When I tried to setup an PPTP/L2TP VPN on one of my CentOS-7 boxes, I googled this script, it works well on my side. Highly recommended if you wanna build your own L2TP VPN server.
Shadowsocks: Install and config on CentOS-7

Shadowsocks: Install and config on CentOS-7

Shadowsocks is a fast tunnel proxy that helps bypass firewall limitations. For more details, you can refer to its homepage. The installation of shadowsocks on CentOS-7 is pretty easy as we just need to run pip, as below: # pip install shadowsocks
Kill an established TCP connection in Linux

Kill an established TCP connection in Linux

Sometimes I need to kill an established TCP session especially the long time running TCP connections that doing barely nothing, without killing the process that opens it.
Smart ways to purge a RabbitMQ queue

Smart ways to purge a RabbitMQ queue

In a recent benchmark, we got a very large queue in one of our online RabbitMQ cluster, which had more than 20mm messages in a single queue (occupying 5-6 gigabytes memory). Then how can we purge the large queue effectively?
RabbitMQ: remove node from cluster

RabbitMQ: remove node from cluster

When a node is no longer meant to be part of a RabbitMQ cluster, we’d remove it explicitly from the cluster. To remove a node from a cluster, there are basically two ways, get itself remove locally, or remove it remotely from the reset nodes. Here suppose we have a cluster consist of three RabbitMQ [...]
Determine the up time of an TCP connection on Linux

Determine the up time of an TCP connection on Linux

As a typical use case for troubleshooting, we may need to find out the up time of an established socket connection. Well, how can we do that inside a running Linux system? I faced this issue this afternoon, and got some luck finally. Note that it’s limited to TCP and UDP.
Find out if a hard drive is SSD or HDD

Find out if a hard drive is SSD or HDD

How can we check whether a hard drive is SSD or HDD? There are two ways for you to find it out. Way 1: On the latest kernels, the SSD disks are automatically detected. You can find the result typically like this: Replace sda with your hard drive path. $ cat /sys/block/sda/queue/rotational 1 You will [...]
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