Slaptijack

OS X CLI: Install VirtualBox

Scott Hebert — Mon, 29 Apr 2013 13:00:26 +0000

I decided the other night to begin doing some testing using my headless Mac Mini. I use VirtualBox for all my testing on my Mac OS X systems. Since the Mini is headless, I decided now was as a good a time as any to start using VirtualBox via the command line. Obviously, installing VirtualBox via the command line is not the same as running VirtualBox via the command line, but installing any package from the command line must be practiced to be remembered.

Download the latest package. I'm using wget which you'll only have if you've specifically installed it. I use MacPorts, but Homebrew is another option.

$ wget http://download.virtualbox.org/virtualbox/4.2.12/VirtualBox-4.2.12-84980-OSX.dmg

Mount the disk image (.dmg). The disk image contents will now be mounted on /Volumes/VirtualBox.

$ hdiutil mount VirtualBox-4.2.12-84980-OSX.dmg

Now, install the package. Note that the target is set to /. In addition to installing VirtualBox in /Applications, this will also put the command line tools in /usr/bin.

$ sudo installer -pkg /Volumes/VirtualBox/VirtualBox.pkg -target /

Now unmount the disk image and clean up.

$ hdiutil unmount /Volumes/VirtualBox/ $ rm VirtualBox-4.2.12-84980-OSX.dmg

Download and install the VirtualBox Extension Pack.

$ wget http://download.virtualbox.org/virtualbox/4.2.12/Oracle_VM_VirtualBox_Extension_Pack-4.2.12-84980.vbox-extpack $ sudo VBoxManage extpack install Oracle_VM_VirtualBox_Extension_Pack-4.2.12-84980.vbox-extpack $ rm Oracle_VM_VirtualBox_Extension_Pack-4.2.12-84980.vbox-extpack

Tech Messages | 2013-03-10

Scott Hebert — Mon, 11 Mar 2013 21:39:00 +0000

A special extended edition of Tech Messages for 2013-03-07 through 2013-03-10:

http://eyeseast.github.com/python-tablefu/
Really looking forward to trying this out. Anyone interested in weighing in with their experiences?
How to selectively kill queries in MySQL? — dba square | A resource on MySQL
Especially helpful when you have hundreds of queries that need to die.
Redis with an SSD swap, not what you want - Antirez weblog

Google Chrome Stuck Overseas

Scott Hebert — Mon, 25 Feb 2013 14:00:23 +0000

I recently spent six weeks in Sydney working for my new job. Naturally, while I was there, I let Google Chrome's omnibox redirect my searches to Google Australia. Fast forward a few weeks, and I'm back in the States, but Chrome is living in the past. After trying just about everything, here is what I finally did to fix it.

First, shut down Google Chrome. Find the Google Chrome default preferences file. On my Mac, that's ~/Library/Application Support/Google/Chrome/Default/Preferences. This is a JSON file. You are looking for an attribute called "last_known_google_url". Mine was set to "https://www.google.com.au/". All I did was change this to "https://www.google.com/".

Good luck!

Asterisk 1.2 Variable Length Limit

Scott Hebert — Mon, 28 Jan 2013 14:00:49 +0000

It seems the maximum length for variables (at least those in extensions.conf) in Asterisk 1.2 is 255 characters. Running into this problem has to be uncommon, but it can really bite you if aren't aware.

Although I am only aware of this limitation in Asterisk 1.2, it might exist in other version as well.

Restart Brother ControlCenter

Scott Hebert — Tue, 06 Nov 2012 14:45:49 +0000

On your Mac, the Brother ControlCenter software that let's you scan an image from your Brother MFC to your computer is started at boot by launchd. Therefore, it can be restarted from the command line.

For example, here is a list of processes controlled by launchd:

$ launchctl list | grep brother
286	-	[0x0-0x17017].com.brother.ControlCenter
282	-	[0x0-0x16016].com.brother.utility.NETserver
281	-	[0x0-0x15015].com.brother.utility.USBserver
266	-	com.brother.LOGINserver

I found that stopping LOGINserver caused all the other services to restart:

$ launchctl stop com.brother.LOGINserver
$ launchctl list | grep brother
36825	-	[0x0-0x258a588].com.brother.ControlCenter
36824	-	[0x0-0x2589587].com.brother.utility.NETserver
36823	-	[0x0-0x2588586].com.brother.utility.USBserver
36818	-	com.brother.LOGINserver

Good luck!

Tech Messages | 2012-10-25

Scott Hebert — Thu, 25 Oct 2012 21:07:04 +0000

A special extended edition of Tech Messages for 2012-10-05 through 2012-10-25:

Stuck at "copying to tmp table"

Scott Hebert — Tue, 04 Sep 2012 16:55:46 +0000

I have a fairly lightly loaded MySQL server with a few tables that are updated every five minutes. Other than these updates, there are very few queries run against the database. The data is queried just a few times per month. Ever so often, one of the more complicated queries will result in the process getting hung in the "copying to tmp table" state. To be honest, the queries that get hung aren't even that complicated. Usually there's one or two joins, a GROUP BY, and an ORDER BY.

So far, when a process gets stuck in this state, I find that killing and restarting the process does not clear up the problem. I've changed my recovery method to killing the process, issuing a FLUSH TABLES, and restarting the process. This has worked fine for me, but I've heard of others that had to resort to restarting the daemon.

Tech Messages | 2012-08-24

Scott Hebert — Sat, 01 Sep 2012 22:00:00 +0000

A special extended edition of Tech Messages for 2012-05-28 through 2012-08-24:

Composing Mercurial commit messages in TextMate
Test-Driven Djano Tutorial
Django is gathering steam. This tutorial introduces you to functional tests and related concepts.
LFS - Lightning Fast Shop
This is an open-source shopping cart built on Python, Django, and jQuery. Has anyone tried it?

Cisco: Telnet/SSH work, HTTP Gives Permission Denied

Scott Hebert — Mon, 27 Aug 2012 13:00:50 +0000

Here are a few tips that might be helpful if you are having trouble accessing your Cisco router or switch via the web server.

Make sure you have the right password! This is pretty obvious, but it's definitely the first thing worth checking.
If you're using aaa new-model, you will need to tell the web server what group to use for authentication: ip http authentication local.
In order to make changes to the device, your user will need access level 15. You can set this with the username command: username slap privilege 15.
It's a good idea to use HTTPS instead of HTTP if possible. Enable that with ip http secure-server. You can disable the non-encrypted web server with no ip http server.
The web server supports a very basic access list. You can lock your web server down even further by limiting who can connect to it. Use ip http access-class 9. Remember to set up your access list first!

Apache Can't Use Remote MySQL Server When SELinux is Enabled

Scott Hebert — Mon, 20 Aug 2012 13:00:20 +0000

I don't know why SELinux problems seem so frustrating. The problem almost certainly is related to the fact that there is frequently no error message. This is exactly the problem I ran into while turning up a new Apache web server on Red Hat Enterprise Linux 6 (RHEL6) with SELinux enabled.

The problem is that SELinux prevents Apache from making network connections by default. This is defined by the SELinux boolean httpd_can_network_connect_db. In order to change this value, issue the following command:

# setsebool -P httpd_can_network_connect_db true

The -P indicates the command is persistent and that the setting should survive reboots.

For reference, here is a list of all httpd-related SELinux booleans and their default values in RHEL6:

# getsebool -a | egrep '^httpd'
httpd_builtin_scripting --> on
httpd_can_check_spam --> off
httpd_can_network_connect --> off
httpd_can_network_connect_cobbler --> off
httpd_can_network_connect_db --> off
httpd_can_network_memcache --> off
httpd_can_network_relay --> off
httpd_can_sendmail --> off
httpd_dbus_avahi --> on
httpd_enable_cgi --> on
httpd_enable_ftp_server --> off
httpd_enable_homedirs --> off
httpd_execmem --> off
httpd_manage_ipa --> off
httpd_read_user_content --> off
httpd_setrlimit --> off
httpd_ssi_exec --> off
httpd_tmp_exec --> off
httpd_tty_comm --> on
httpd_unified --> on
httpd_use_cifs --> off
httpd_use_gpg --> off
httpd_use_nfs --> off
httpd_use_openstack --> off