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Control Group Subsystems in RHEL7

Control groups (cgroups) are a Linux kernel feature that enables you to allocate resources — such as CPU time, system memory, disk I/O, network bandwidth, etc. — among hierarchically ordered groups of processes running on a system. Initially developed by Google engineers Paul Menage and Rohit Seth in 2006 under the name “process containers”, it was merged into kernel version 2.6.24 and extensively enhanced since then. RHEL6 was the first Red Hat distribution to support cgroups. Cgroups provide system administrators with fine-grained control over allocating, prioritizing, denying, managing, and monitoring system resources. A cgroup is a collection of processes that

RHEL7 Does Not Support User Namespace

The Linux kernel currently implements six (out of 10 proposed) namespaces for process separation: mnt – mount points, filesystems pid – processes net – network stack ipc – System V IPC uts – hostname, domainname user – UIDs, GIDs The last Linux namespace to be fully implemented was the user namespace (CLONE_NEWNS) whose implementation was finally completed in the 3.8 kernel after being started in the 2.6.23 kernel. The current kernel in RHEL7 is 3.10.0-121. Unfortunately it does not include the user namespace. According to Dan Walsh of Red Hat: We hope to add the user namespace support to a

Enable VMware Workstation tools in RHEL7

If you install the minimum version of Red Hat Enterprise 7 as a VMware Workstation guest, you will have to overcome a number of obstacles to installing the VMware Tools. Firstly, no ifconfig utility is installed. To install this utility, install the net-tools package. # yum install net-tools Next, check to see if the open-vm-tools package was installed. If not install it from your DVD or ISO. You may have to first create a repo entry similar to the following: [dvd] name=red Hat Enterprise Linix [DVD] baseurl=file:///run/media/<FIXTHIS>/RHEL-7.0 Server.x86_64 enabled=1 gpgcheck=0 and then run: # yum install open-vm-tools I found that

Mask V Disable a Systemd Service Unit

In the systemd world, you should be aware of the difference between disabling and masking a service unit. To prevent a service unit that corresponds to a system service from being automatically started at boot time: # systemctl disable name.service When invoked systemd reads the [Install] section of the selected service unit and removes the appropriate symbolic link. In RHEL7, for example, the symbolic link would be to the /usr/lib/systemd/system/name.service file from the /usr/lib/systemd/system/ directory. Every service unit that is known to systemd may be started if it is needed – even if it is disabled. To explicitly tell systemd