Month: June 2014

iMac Fan Control Work-Around

I was recently repairing a 24″ iMac (EMC 2211, Model A1225); to get the
computer up and running again I needed to replace the hard drive. This model
iMac has a sensor that attaches to the hard drive to report temperature metrics
for fan control. The replacement hard drive did not accommodate this sensor so
when the iMac booted up, the fan automatically went to full (and loud) speed.
This is how I revved down and quieted the fan.

The first thing I did was search the Web for a way to interface with
whatever OS X built-in software controls the fan speed. This was not
forthcoming, but in my search I found third-party applications that professed
to be able to help me achieve my ultimate goal of quieting down the fan. One
that came highly recommended was
but when I installed it the GUI only provided a way to set the minimum fan
speed (in RPMs). I needed a way to control the max fan speed.

Thankfully the author of this program, Hendrik Holtmann, opened sourced his
work. I visited the github
for the project and discovered that smcFanControl had a command line
utility that allowed me to set the max speed.

This utility is located inside the and is called
smc. The instructions for using the utility are on this
page. The first thing I had to do was switch the fan from auto to
forced mode so that I can make adjustments and apply them. First I tried
to set a target speed for the fan, but when I did that it sounded like the fan
went down to the target speed then right back up to the max. So I went ahead
and set the max speed (adjusting to find the highest RPMs at the lowest noise).
Now I could use the computer without the fan blasting, but these settings would
vanish on reset so I set up a cronjob to apply them at reboot.


The Script

When I downloaded and extracted the app, I placed it into
/Applications/Utilities and I placed the startup script in my
$HOME directory and named it


# switch from auto to forced mode
/Applications/Utilities/ -k "FS! " -w 0004

# set the max fan speed (in rpms)
/Applications/Utilities/ -k F2Tg -w 2300

The crontab

Access the crontab for editing:

~$> sudo crontab -e

Add this to the crontab

@reboot /Users/jason/

Installing an OS in VirtualBox on a Headless FreeBSD Server

Using Virtualization one is able to run a full computer operating system inside of an existing operating system. I’ve been using VirtualBox for years to virtualize many kinds of operating systems for many different reasons on my desktop computers. I first started using VirtualBox to run a Windows installation so I could do things I needed to do in Windows that I had not yet figured out how to do with a free/open source operating system (at that time Ubuntu). As I came to familiarity with *nix platforms, I wanted to try out new techniques I learned and I used VirtualBox to accomplish this. With this program I could have a sandbox where I could easily create, save, snapshot and destroy virtual desktops, servers, and networks. On my new FreeBSD server I wanted to use virtualization to create test servers that I could use while I learn about new software and refine what I know about system administration and computer programming.

The thing this time around is my server has no dedicated monitor. I’ve always used the GUI to interact with the VirtualBox software, but now I needed a way to do all the things I do with VirtualBox with a Command Line Interface (CLI). And that’s how I became introduced to VBoxManage. If you have your system’s VirtualBox package installed you should have VBoxManage installed as well:

~$> VBoxManage
Oracle VM VirtualBox Command Line Management Interface Version 4.3.10_OSE
(C) 2005-2014 Oracle Corporation
All rights reserved.


VBoxManage [] General Options: [-v|--version] print version number and exit [-q|--nologo] suppress the logo [--settingspw ] provide the settings password
[--settingspwfile ] provide a file containing the settings password


list [--long|-l] vms|runningvms|ostypes|hostdvds|hostfloppies|
---output omitted---

Typing in VBoxManage every time I wanted to issue a command to VirtualBox did not appeal to me at all so I quickly made a bash alias:

~$> echo "alias vbm='VBoxManage'" >> .bash_aliases && source .bash_aliases

Before we go any further, VirtualBox requires some kernel modules to be loaded.

~$ sudo kldload vboxdrv
~$ sudo kldload vboxnetadp

Okay, now we can get some work done. First create the VM and the virtual disk this machine will use.

~$ vbm createvm --name t0 --ostype FreeBSD --register
UUID: e18a1e47-69a0-4487-8114-2d4381141d32
Settings file: '/home/jason/VirtualBox VMs/t0/t0.vbox'
~$ vbm createhd --filename VirtualBox\ VMs/t0/t0.vdi --size 2000
Disk image created. UUID: 1a1ff4fa-db67-4b1b-b597-fd0453ed82ac

We can now list out the VMs to verify we created the device, then take a look at the profile of a virtual machine with the showvminfo command.

~$ vbm list vms
"t0" {e18a1e47-69a0-4487-8114-2d4381141d32}
~$ vbm showvminfo t0
---output omitted---
~$ ls VirtualBox\ VMs/t0/
t0.vbox t0.vbox-prev t0.vdi

Now that the machine exists (virtually), we need to install a storage bus, and then add devices – namely a hard drive and a dvd drive – to it.

~$ vbm storagectl t0 --name sata_bus --add sata --portcount 4 --bootable on
~$ vbm storageattach t0 --storagectl sata_bus --port 1 --type hdd --medium VirtualBox\ VMs/t0/t0.vdi
~$ vbm storageattach t0 --storagectl sata_bus --port 2 --type dvddrive --medium downloads/FreeBSD-10.0-RELEASE-i386-disc1.iso

Let’s verify:

~$ vbm showvminfo t0|grep sata_bus
Storage Controller Name (0): sata_bus
sata_bus (1, 0): /usr/home/jason/VirtualBox VMs/t0/t0.vdi (UUID: 1a1ff4fa-db67-4b1b-b597-fd0453ed82ac)
sata_bus (2, 0): /usr/home/jason/downloads/FreeBSD-10.0-RELEASE-i386-disc1.iso (UUID: c277d5b5-e7e6-4172-9ea7-253a5a23d38e)

So there exists a virtual machine and it has a blank virtual hard drive and a dvd drive installed. Inside the dvd drive is the FreeBSD installation disc. At this point we could start the VM and install the OS, but how do we connect to the virtual server? Well we need to install a virtual network interface card and setup bridged networking. This will allow us to easily connect to the VM and give it access to the Internet so we can download any packages necessary for installation.

~$ ifconfig
ath0: flags=8802 metric 0 mtu 2290
ether 00:25:56:22:d5:60
nd6 options=21 media: IEEE 802.11 Wireless Ethernet autoselect (autoselect) status: no carrier alc0: flags=8843 metric 0 mtu 1500
options=c3198 ether 00:23:5a:e0:0e:42 inet netmask 0xfffffff0 broadcast inet6 fe80::223:5aff:fee0:e42%alc0 prefixlen 64 scopeid 0x2 nd6 options=29 media: Ethernet autoselect (100baseTX )
status: active
lo0: flags=8049 metric 0 mtu 16384
options=600003 inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3 inet netmask 0xff000000 nd6 options=21 ~$ vbm modifyvm t0 --nic1 bridged --bridgeadapter1 alc0 --nictype1 82540EM ~$ vbm showvminfo t0 | grep NIC NIC 1: MAC: 08002770C671, Attachment: Bridged Interface 'alc0', Cable connected: on, Trace: off (file: none), Type: 82540EM, Reported speed: 0 Mbps, Boot priority: 0, Promisc Policy: deny, Bandwidth group: none NIC 2: disabled NIC 3: disabled NIC 4: disabled NIC 5: disabled NIC 6: disabled NIC 7: disabled NIC 8: disabled

Above, the first thing that I did was list out the network interfaces of the physical machine (with ifconfig). I did this to determine the which network interface I was going to bridge to (the one connect to the outside network). Each VM can have 8 NICs. With second command I set NIC 1 to be a bridged interface to alc0, my wired ethernet, and to emulate an Intel 82540EM Gigabit Ethernet Controller. Now when the VM powers up it will have network connectivity.

Now we can install the operating system. Because the FreeBSD install disc does not establish an IP address without user interaction, I needed to forward X11 through my SSH connection. At first I received an error when I tried to do the X11 forwarding, but I followed this tutorial and cleared that error.

jason@desktop ~$ ssh -X jason@hostserver
~$ # I connected to host server with ssh -X for ssh forwarding
~$ # now I start the vm on the host server and I can interact
~$ # with it with the GUI on my desktop
~$ vbm startvm t0

With our setup the VM will boot the FreeBSD installation media in our dvd drive

After the OS is installed, you’ll want to eject the dvd drive so that when you reboot, you won’t reboot back into the install cd.

~$ vbm storageattach t0 --storagectl sata_bus --port 2 --medium none

Now the OS is installed and (if you set it up that way) it will obtain an IP address on boot and start the SSH server that you can connect to from another machine

~$ vbm startvm t0 --type headless
Waiting for VM "t0" to power on...
VM "t0" has been successfully started.