Crappy Power

I've had some problems in the somewhat recent past where my UPS goes into panic mode and because the battery was old / crappy, this made things "very bad". I've had no issues since replacing the battery, but now I'm getting a picture of why it was so awful from apcupsd:

Mon Aug 31 11:13:36 PDT 2009  Power is back. UPS running on mains.
Mon Aug 31 11:13:34 PDT 2009  Power failure.
Thu Aug 27 11:20:20 PDT 2009  Power is back. UPS running on mains.
Thu Aug 27 11:20:18 PDT 2009  Power failure.
Sat Aug 22 16:59:32 PDT 2009  Power is back. UPS running on mains.
Sat Aug 22 16:59:29 PDT 2009  Power failure.
Sat Aug 22 16:56:29 PDT 2009  Power is back. UPS running on mains.
Sat Aug 22 16:56:27 PDT 2009  Power failure.
Fri Aug 21 00:12:33 PDT 2009  Power is back. UPS running on mains.
Fri Aug 21 00:12:31 PDT 2009  Power failure.
Fri Aug 21 00:11:52 PDT 2009  Power is back. UPS running on mains.
Fri Aug 21 00:11:50 PDT 2009  Power failure.
... etc

There are a lot of power events going on. Given that the time of the "power failure" is always 2 seconds, my guess is that this just means power is fluctuating. I've lived in places where this happened a bit and where it happened not at all, but this is the worst I've seen.

The only thing I can say is: get a UPS if you don't have one! You may not need battery backup per se, but this is the kind of stuff that will send the power supply unit in your PC to an early grave. And if you're unlucky, the PSU may just take other components of your PC with it.

- Archangel

Rolling dice in Bash

I often need short random numbers at work. For example, if I'm scheduling a whole bunch of servers to do the same automated tasks and I want them to not run at exactly the same time, I'll use a random number between 1 and 60 to have them run on different minutes. You can do this somewhat easily in bash using the $RANDOM variable and a mod operation like so:

echo $((RANDOM%60))

However, it's a bit long to type and sometimes I need batches of numbers. So I looked around at dice rolling programs but most were too fancy. So I wrote a simple simple script I called "roll" which returns sets of random numbers.

#!/bin/bash

# Roll
#   This script returns the values and sum of a set of dice rolls.  The first 
#   arg is optional and gives a number of dice.  The second arg is the number 
#   of sides on the dice.  For example "roll 2 6" will give two values from 1 
#   to 6 and also returns their sum.
#
# (c)2009 Dominic Lepiane 

sides=6
dice=1
total=0
c=0

if [ $# = 2 ] ; then
        dice=$1
        sides=$2
elif [ $# = 1 ] ; then
        sides=$1
else
        echo "Usage: $0 [# of dice] <# of sides>" >&2
        exit -1
fi

#echo "Rolling {$dice}d{$sides}"

while [ $c -lt $dice ] ; do
        c=$((c+1))
        roll=$((RANDOM%sides + 1))
        total=$((total+roll))
        echo -n "$roll "
done

if [ $dice -gt 1 ] ; then
        echo -n " = $total"
fi

echo ""

So if I want 12 numbers from 1 to 60, it looks like this:

./roll 12 60
21 32 30 38 56 36 27 19 25 34 25 48  = 391

Very handy!

VMware and Unity

I've been running Fedora 11 (x64) on my workstation at work and running Windows XP (32b) in a VMware virtual machine. It was a VM I'd created with server so all I needed to run it was the free VMware Player.

First, installing VMware Player was a bit of a problem. The install from RPM didn't work, it hosed initially. Then the install from the bundle also failed... Much like it does for many users Online it turned out so there was a community-created patch which worked just fine.

Then there was running the VM. Initially, it seemed great. I was running Windows XP full-screen on my right-screen and had my Fedora desktop / apps on my left screen. But it was pretty wonky about mouse control so I got to the point where I was firing up the Windows VM only when I needed it and then not in full-screen mode.

But I discovered that VMware's Unity mode helps bridge the gap. It pulls you out of console mode and launches any apps from the guest VM in their own windows in your desktop environment. This is especially useful for say, running MSIE or MS Outlook. It's still a little weird because the apps *look* like they should be running natively yet the responsiveness is clearly far behind local apps, but the only real gap is that I can't Shift+Right-Click -> Run As... on tools like Active Directory Users and Computers (which I need). I tried switch back to the console, doing the Run As... and then switching back to Unity, but the escalated app doesn't show up.

Well, it's great and closes the gap some, but for now I'll just keep updating Player and Tools and see if eventually that full-screen mode just gets fixed and works transparently.

- Arch

SpamAssassin

On previous mail server setups, I've tried to pass all mail coming into the server through SpamAssassin (The Fight Against Spam) and it's a bit of a struggle to get it working sometimes so I've had nothing setup for a while other than some SMTP restrictions and a couple of the RBLs. So since SpamAssassin is generally geared to being run / configured per-user, I figured, what the hell, I'll try that. And it is way easier. All I did was plop this in my .procmailrc:

# SpamAssassin
:0fw: spamassassin.lock
| /usr/bin/spamassassin

:0:
* ^X-Spam-Status: Yes
Junk

So now, SA happily tags all my possibly spammy mail and then for actual spam, it dumps it in the Junk folder and it actually strips the content replacing it with all the reasons why the message was identified as spam (the original message is attached).

So far so good!

- Arch

Using proc to force a reboot

So we just had this little discussion on IRC and I figured I'd save it for posterity here:

[11:37:36]  to force a 'hard' reboot (if reboot is not working) - equivalent to pulling the power cable:
[11:37:44]  echo 1 > /proc/sys/kernel/sysrq; echo b > /proc/sysrq-trigger
[11:40:45]  come on dom, you know you want to try it.
[11:41:21]  heh
[11:42:29]  what's this do?  what's this do?  what's it do???
[11:43:13]  you tell us
[11:47:09]  yeah, that's awesome
[11:47:24]  it just tells BIOS to reboot
[11:47:35]  (or something like that anyhow)
[11:47:58]  so, immediate reboot in other words?
[11:47:58]  system just goes *blip* and starts posting

So there you go. Want to reboot without waiting for all those nasty processes to finish or phyiscally pressing the power button? That's your way out.

Thanks, toddz :D

- Arch

Apache and LDAP users

Requisites:

Apache 2.2
mod_authnz_ldap (and enabled with a2enmod authnz_ldap under Debian+Ubuntu)

In your httpd.conf or your htaccess file, add the following:

    # Access control for this directory
    AuthBasicProvider ldap
    AuthType Basic
    AuthName "Password Required"

    AuthLDAPURL "ldap://localhost:389/OU=Users,DC=example,DC=com?sAMAccountName?sub?(objectClass=*)" NONE

    AuthLDAPBindDN readonly@example.com
    AuthLDAPBindPassword plaintextpassword

    Require ldap-group CN=somegroup,OU=someou,OU=Groups,DC=example,DC=com

This example is for connecting to an MS Active Directory server. For an OpenLDAP server, you may find that you don't need the BindDN/Pass options and you need uid instead of sAMAccountName (or possibly just "ldap://localhost/DC=domain,DC=tld").

If you look at other sites online, you'll find that a lot of users say they have to fiddle the config to get it working. Some of the common things I saw were:

1. Setting "AuthzLDAPAuthoritative off"


2. Specifying at least one container under the base DN (as in my example)


3. Tweaking the GroupAttribute and GroupIsDN options


4. Using a DN for the AuthLDAPBindDN (UPN used in my example)


5. Enabling SSL or TLS


6. Multiple domain controllers (simply specify them separated by spaces in your URL)


7. Filters with "Require ldap-filter"

... As you can see there can be a lot of tweaking for specific sites. But all-in-all, the basic configuration is quite simple. If your LDAP server allows anonymous searches, you really only need the AuthLDAPURL line and it can be as simple as "ldap://localhost/DC=example,DC=com".

- Arch

Google Apps

One of the cool services that Google offers is the hosting of various services for your domain. Basically, you can brand Google with your own domain including mail, calendar, chat, docs, sites and "mobile" (I haven't used "mobile", but it includes sync services). The service is called Google Apps.

The "standard edition" is pretty much the standard services and limits you to 50 user accounts. And 50 people is quite a few for a personal domain or even a small business. Once you need more features or more accounts, its $50 / year per account. Which, truth be told, is pretty cheap since even just paying for anti-spam/anti-virus filtering is about $30 / year for pretty basic service from Symantec of whomever.

At any rate, I found it a bit confusing at first but mostly because I was setting this up in a sub-domain (dl.thenibble.org) on GoDaddy. But once I got in, it's pretty easy. You get this dashboard which shows you which services are activated and you can just click on whichever ones you want and if DNS changes are required, it will tell you and give you pretty specific instructions. But there's a lot. You have to do one just to activate the domain, add aliases for all your services (unless you want to use google.com/apps/mydomain or whatever), and then for email, there's 5 MX records and for chat there's about 10 SRV records.

But now that it's all setup, it's pretty fancy. You can create email groups, use docs, publish calendars, etc. I tried poking around a bit and really all that Google does for stuff like "sites" when you create an alias under your domain is it just redirects the user to sites.google.com/domain/whatever ... So it won't be a replacement for having a web host. But for email, it will just accept mail at your domain so it's a full email service.

And standard edition is free. Did I mention that? Yeah, it's ad-supported, but otherwise free.

Fun!
- Arch