Eddie's Blog

Lunch Hour Workout

New Year resolution, but no time to work out? Try a lunch hour workout. Keep the following in mind.

Everything counts. Don't have to take place at a gym. Walking (e.g. 30 minutes) around the office counts.

According to the fitness experts, eat after, not before, the workout

Do some in-office stretch, bends, push-ups.

Windows 8 Tools

Classic Shell for Windows 8 (free): brings back the Start menu and button (and more) on Windows 8.
Virtual Router Plus (free): turns any Windows 7 and Windows 8 computer into a Wifi Hot Spot.

vCenter “Hardware monitoring service on this host is not responding or not available” in Hardware Status tab

Fix: In vCenter, select the VM host, Configuration, Security Profile (under Software), Firewall Properties, CIM Server, Options, Restart.

After restarting the CIM Server service, it can take a few minutes before the hardware status is updated.

Tested in ESXi 5.0

Reference: http://communities.vmware.com/thread/219556?start=15&tstart=0

Watt and Volt-Amp (VA) Rating Notes

1. Definition and Purpose

Watt is the real power drawn by the equipment. The Watt rating to determine the actual power purchased from the utility company and the heat loading generated by the equipment.
The VA rating is used for sizing wiring and circuit breakers.

2. IT Equipment Switching Power Supply Types

Power Factor Corrected supply (PFC)
Capacitor Input supply

3. Computer Equipment Watt and VA Rating

Large computer equipment such as routers, switches, arrays, and servers made after 1996 use the PFC supply. Watt rating = VA rating
PCs, small hubs, PC accessories, and larger computer equipment made prior to 1996 typically use Capacitor Input supply. Watt rating = 0.55 ~ 0.75 * VA rating

4. UPS Watt an VA Rating

Small UPS: Watt rating = 60% * VA rating (a de-facto standard in the industry)
Larger UPS: Watt rating = VA rating

5. Conclusion

Neither the Watt nor the VA rating of a UPS may be exceeded
Sizing the VA rating of a load to be no greater than 60% of the VA rating of the UPS ensures the Watt rating of a load not to exceed the Watt rating of the UPS. This conservative sizing approach will typically oversize the UPS and provide additional run time.

Source: APC White Paper #15 “Watts and Volt-Amps: Powerful Confusion”

Troubleshoot PEAP Authentication

Environment:

Wireless PEAP with Windows Active Directory domain authentication is configured. (see http://www.techrepublic.com/article/ultimate-wireless-security-guide-an-introduction-to-peap-authentication/6148543 for the setup detail).

Windows Server 2003 with a self-signed digital certificate as the RADIUS server.

Wireless access managed by the Active Directory “WiFi Users” security group.

Access Point: Cisco WAP4410N with firmware 2.0.5.3

Access Point Configuration:

Discovery (By Bonjour): Enabled
Wireless Security Mode: WPA2-Enterprise Mixed (WPA Algorithm: TKIP or AES)
Primary RADIUS Server: Windows Server 2003 RADIUS server IP address
Primary RADIUS Server Port: 1812
Wireless Connection Control (MAC address filter): Disabled

Problem:

The users in the Active Directory “WiFi Users” security group were able to authenticate and access the wireless with the wireless devices (iPhone, iPad, Windows Phone 7.5, Windows XP with SP3, Windows 7, MAC OS X, etc) configured with the PEAP authentication. One day in August 2012, the Windows Server 2003 RADIUS server was updated with the latest Microsoft security updates. Then, only iOS devices (maybe MAC OS X too) can authenticate and access the wireless; all Windows based devices keep getting the connection failure even the configuration and authentication are correct.

Troubleshoot:

The RADIUS server System log shows a warning from source IAS, event ID 2. The user was denied access; Reason-Code = 266; Reason = The message received was unexpected or badly formatted.

Solution:

The scenario 2 in the KB article (http://support.microsoft.com/kb/933430) matches this issue. Use method 3 in the KB article resolved the problem.

Linux “No space left on device” Error

symptom:

a web site is down, but the httpd (in my case lighttpd) service started okay. restarting the service still has the same problem.

touch test_file, get the “No space left on device” error

df –h, show a lot of free disk space

Filesystem            Size Used Avail Use% Mounted on
/dev/sdb1              10G 2.8G 6.8G 29% /
/dev/sda1              99M   21M   74M 22% /boot
tmpfs                 125M     0 125M   0% /dev/shm

problem:

out of inodes

Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/sdb1             655776 655776       0 100% /
/dev/sda1              26208      38   26170    1% /boot
tmpfs                  31871       1   31870    1% /dev/shm

fix:

find the files of a certain size (e.g. great than three blocks in this example) to locate these files (in my case is the ruby session files in /srv/www/lighttpd/rails/tmp/sessions, the file name is ruby_sess.xxxxxxxx)

find / –size +3 –print

but rm –f ruby_sess.* failed because “bash: /bin/rm: Argument list too long” (see http://en.kioskea.net/faq/1086-unable-to-delete-file-argument-list-too-long)

ls ruby_sess.* | xargs rm get “-bash: /usr/bin/ls: Argument list too long”

find . –type f –name ruby_sess.* | xargs rm get “-bash: /usr/bin/find: Argument list too long”

finally find . –name “ruby_sess.*” | xargs rm worked

Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/sdb1             655776 122320 533456   19% /
/dev/sda1              26208      38   26170    1% /boot
tmpfs                  31871       1   31870    1% /dev/shm

Delete “Account Unknown” Local User Profiles

Issue:

On Windows XP or Server 2003, under Control Panel / System / Advanced / User Profiles / Settings, there are some “Account Unknown” user profile, but the Delete button is grayed out. And when try to delete the profile from “c:\documents and settings” folder, the error message is “Cannot delete NTUSER.DAT: It is being used by another person or program. Close any programs that might be using the file and try again.”