August 2014 – put things down

In another post I described how to install CentOS 6 via a kickstart file (be sure to check out the “Kickstart Sample Configuration” section). CentOS 7 was recently released, and with that I needed to also use a kickstart configuration. However, simply using the previous kickstart configuration was not as easy as copy-and-paste (besides updating the release version in the repository configuration).

Summary of Kickstart Changes

There were a few changes that needed to be made for a base/core installation of CentOS 7:

Include eula --agreed (read the documentation)
Include services --enabled=NetworkManager,sshd (read the documentation)
Update the install packages list ( %packages section)
CentOS 7 is also a bit more strict with the kickstart file, so I had to explicitly include %end where applicable
CentOS 7’s default file system is now xfs, in CentOS 6 it was ext4, so consider updating the automatic partitioning to use xfs
Package groups @scalable-file-systems, @server-platform, @server-policy, and @system-admin-tools no longer exist – I haven’t located suitable replacements yet
Things like ifconfig are no longer included by default (they are now deprecated), so if you need them be sure to include net-tools. You should be using ip by now anyway.

Kickstart Sample Configuration

And now, an updated kickstart config for CentOS 7, with consideration of the previously mentioned updates (compare it with the previous Kickstart Sample Configuration mentioned in the other post). I also chose to include some extra packages that don’t exist by default with a @core installation.

#version=RHEL7
install
nfs --server=repo.hostname.tld --dir=/repo/centos/7/os/x86_64
lang en_US.UTF-8
keyboard --vckeymap=us --xlayouts='us'
zerombr
eula --agreed
services --enabled=NetworkManager,sshd
reboot

# leaving network in here, but it'll be dhcp for now, make sure you have KVM access
#network --onboot no --device eth0 --bootproto static --ip 172.16.0.254 --netmask 255.255.0.0 --gateway 172.16.1.1 --noipv6 --nameserver 172.16.0.2 --hostname new.hostname.tld
rootpw --iscrypted DEFAULT_SALTED_ROOT_PASSWORD
firewall --service=ssh
auth --enableshadow --passalgo=sha512
selinux --enforcing
timezone America/Phoenix --isUtc --ntpservers=0.centos.pool.ntp.org,1.centos.pool.ntp.org,2.centos.pool.ntp.org,3.centos.pool.ntp.org

### LVM
bootloader --location=mbr --boot-drive=sda
clearpart --all --drives=sda
ignoredisk --only-use=sda

part /boot --fstype="xfs" --ondisk=sda --size=256
part pv.01 --fstype="lvmpv" --ondisk=sda --grow --size=1

volgroup vg_main pv.01
logvol / --fstype="xfs" --name=lv_root --vgname=vg_main --grow --size=8192
logvol swap --fstype="swap" --name=lv_swap --vgname=vg_main --grow --size=4096 --maxsize=4096

%packages
@core
net-tools
policycoreutils
screen
tree
vim
wget
%end

%post
wget http://your.hostn.tld/scripts/c7/post-install.sh -O post-install.sh
sh post-install.sh
rm -f post-install.sh
%end

#version=RHEL7

install

nfs --server=repo.hostname.tld --dir=/repo/centos/7/os/x86_64

lang en_US.UTF-8

keyboard --vckeymap=us --xlayouts='us'

zerombr

eula --agreed

services --enabled=NetworkManager,sshd

reboot

# leaving network in here, but it'll be dhcp for now, make sure you have KVM access

#network --onboot no --device eth0 --bootproto static --ip 172.16.0.254 --netmask 255.255.0.0 --gateway 172.16.1.1 --noipv6 --nameserver 172.16.0.2 --hostname new.hostname.tld

rootpw --iscrypted DEFAULT_SALTED_ROOT_PASSWORD

firewall --service=ssh

auth --enableshadow --passalgo=sha512

selinux --enforcing

timezone America/Phoenix --isUtc --ntpservers=0.centos.pool.ntp.org,1.centos.pool.ntp.org,2.centos.pool.ntp.org,3.centos.pool.ntp.org

### LVM

bootloader --location=mbr --boot-drive=sda

clearpart --all --drives=sda

ignoredisk --only-use=sda

part /boot --fstype="xfs" --ondisk=sda --size=256

part pv.01 --fstype="lvmpv" --ondisk=sda --grow --size=1

volgroup vg_main pv.01

logvol / --fstype="xfs" --name=lv_root --vgname=vg_main --grow --size=8192

logvol swap --fstype="swap" --name=lv_swap --vgname=vg_main --grow --size=4096 --maxsize=4096

%packages

@core

net-tools

policycoreutils

screen

tree

vim

wget

%end

%post

wget http://your.hostn.tld/scripts/c7/post-install.sh -O post-install.sh

sh post-install.sh

rm -f post-install.sh

%end

VMware Tools Change

If you’re like me and use ESXi, I’m currently on version 5.5 and 5.5u1, the installable tools for integrating with ESXi is a nice treat. However, the repository location has changed specifically for RHEL7, and so have the packages.

The new repository location is at http://packages.vmware.com/packages/rhel7/x86_64/.
The only package that needs to be installed is open-vm-tools.
Note that the tools are currently only available for the x86_64 architecture, but I’m still including $basearch in the URL.
The “packages” repo at packages.vmware.com does not include a GPG Key, but it is the same one from the older “tools” repo.

Add VMware Tools to YUM

Put the following repo configuration in /etc/yum.repos.d/vmware-tools.repo:

[vmwarec7]
name=VMware Tools - $basearch
baseurl=http://packages.vmware.com/packages/rhel7/$basearch/
gpgkey=http://packages.vmware.com/tools/keys/VMWARE-PACKAGING-GPG-RSA-KEY.pub
gpgcheck=1
protect=1
enabled=1

[vmwarec7]

name=VMware Tools - $basearch

baseurl=http://packages.vmware.com/packages/rhel7/$basearch/

gpgkey=http://packages.vmware.com/tools/keys/VMWARE-PACKAGING-GPG-RSA-KEY.pub

gpgcheck=1

protect=1

enabled=1

Then update yum and install the tools:

# clean yum's cache
yum clean all
# reload yum.repos.d
yum check-update
# install the package
yum install open-vm-tools

# clean yum's cache

yum clean all

# reload yum.repos.d

yum check-update

# install the package

yum install open-vm-tools

Read this SO question first: Removing event listener which was added with bind

Now that we’re on the same page. I’m going to make this short’n’sweet by providing a premise and letting the code do the talking: The example provided in the SO post was all fine and dandy, but was for the case of single-use. I needed a way to clean up event listeners on a Node.js net.Server and associated socket connections.

/*
 * First, the setup:
 * 1. bring in deps
 * 2. create an object that will be an emitter
 * 3. inherit the core events emitter functionality
 * 4. register a method that will eventually emit an event
 * 5. staticDefinition is just some plain-old function we might use
 * 6. instantiate our custom event emitter class
 * The actual "ah-ha!" is after the setup.
 */
var events = require('events');
var util = require('util');

var EventClass = function() {};

util.inherits(EventClass,events.EventEmitter);

EventClass.prototype.emitSomething = function(name) {
	var t = process.hrtime();
	this.emit.apply(this,[name,t[0]*1e9+t[1],name].concat(Array.prototype.slice.call(arguments,1)));
};

function staticDefinition() {
	console.log.apply(console,['staticDefinition'].concat(Array.prototype.slice.call(arguments,0)));
}

var inst = new EventClass();

/* eventsTable is used to keep track of bound events within a specific scope/ns
 * notice this is a kvp table, i.e. { 'eventName': function eventHandler(){} }
 * so multiple listeners on a single event won't work
 * but this shows how something like this be implemented
 */
var eventsTable = {};

// first, let's show the typical way of doing things
inst.on('simple',staticDefinition); // register event listener
inst.emitSomething('simple',1,2); // do something to trigger the underlying emitter
console.log(inst.listeners('simple').length); // 1, we see that it has an emitter for our event
inst.removeListener('simple',staticDefinition); // usual way of removing it
console.log(inst.listeners('simple').length); // 0, works, the listener was removed

// this will dynamically attach a bunch of events with diff parameters that have been manipulated with bind
['one','two','three'].forEach(function(eventName,key) {
	var specificDefinition = staticDefinition.bind(inst,'custom'+key); // each definition is unique
	eventsTable[eventName] = specificDefinition; // register the event in the table
	inst.on(eventName,specificDefinition); // bind it
});

// try to remove the listener with the basic function definition
inst.emitSomething('one',3,4);
console.log(inst.listeners('one').length); // 1
inst.removeListener('one',staticDefinition); // doesn't work
console.log(inst.listeners('one').length); // 1

// try to remove the listener with the exact bind spec (new function definition)
inst.emitSomething('two',5,6);
console.log(inst.listeners('two').length); // 1
inst.removeListener('two',staticDefinition.bind(inst,'two')); // doesn't work
console.log(inst.listeners('two').length); // 1

inst.emitSomething('three',7,8);
console.log(inst.listeners('three').length); // 1
inst.removeListener('three',eventsTable['three']); // works
console.log(inst.listeners('three').length); // 0

* First, the setup:

* 1. bring in deps

* 2. create an object that will be an emitter

* 3. inherit the core events emitter functionality

* 4. register a method that will eventually emit an event

* 5. staticDefinition is just some plain-old function we might use

* 6. instantiate our custom event emitter class

* The actual "ah-ha!" is after the setup.

var events = require('events');

var util = require('util');

var EventClass = function() {};

util.inherits(EventClass,events.EventEmitter);

EventClass.prototype.emitSomething = function(name) {

var t = process.hrtime();

this.emit.apply(this,[name,t[0]*1e9+t[1],name].concat(Array.prototype.slice.call(arguments,1)));

};

function staticDefinition() {

console.log.apply(console,['staticDefinition'].concat(Array.prototype.slice.call(arguments,0)));

}

var inst = new EventClass();

/* eventsTable is used to keep track of bound events within a specific scope/ns

* notice this is a kvp table, i.e. { 'eventName': function eventHandler(){} }

* so multiple listeners on a single event won't work

* but this shows how something like this be implemented

var eventsTable = {};

// first, let's show the typical way of doing things

inst.on('simple',staticDefinition); // register event listener

inst.emitSomething('simple',1,2); // do something to trigger the underlying emitter

console.log(inst.listeners('simple').length); // 1, we see that it has an emitter for our event

inst.removeListener('simple',staticDefinition); // usual way of removing it

console.log(inst.listeners('simple').length); // 0, works, the listener was removed

// this will dynamically attach a bunch of events with diff parameters that have been manipulated with bind

['one','two','three'].forEach(function(eventName,key) {

var specificDefinition = staticDefinition.bind(inst,'custom'+key); // each definition is unique

eventsTable[eventName] = specificDefinition; // register the event in the table

inst.on(eventName,specificDefinition); // bind it

});

// try to remove the listener with the basic function definition

inst.emitSomething('one',3,4);

console.log(inst.listeners('one').length); // 1

inst.removeListener('one',staticDefinition); // doesn't work

console.log(inst.listeners('one').length); // 1

// try to remove the listener with the exact bind spec (new function definition)

inst.emitSomething('two',5,6);

console.log(inst.listeners('two').length); // 1

inst.removeListener('two',staticDefinition.bind(inst,'two')); // doesn't work

console.log(inst.listeners('two').length); // 1

inst.emitSomething('three',7,8);

console.log(inst.listeners('three').length); // 1

inst.removeListener('three',eventsTable['three']); // works

console.log(inst.listeners('three').length); // 0

Month: August 2014

Migrating Kickstart from CentOS 6 to CentOS 7 + ESXi VMware Tools

Summary of Kickstart Changes

Kickstart Sample Configuration

VMware Tools Change

Add VMware Tools to YUM

Node.js: Dynamic Event Listener Binding and Removal