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August 12, 2009

Logging into a VMware Server stuck on the “Loading…” Page

Filed under: Linux,Virtualization — Matt @ 8:45 pm

VMware Server is a handy app to run in places where server virtualization is needed, but you can’t justify the expense or effort required to setup a VMware ESXi or Xen host. One of the reoccurring problems that I run into, even on lightly loaded servers is when trying to log into the VMware Infrastructure Web Access interface, the browser gets stuck at “Loading…”, and never brings up the login form. I’ve observed this on Firefox in Linux, Mac OS X and Windows; as well as within Internet Explorer.

It turns out that the fix for this doesn’t involve the browser at all, but rather a VMware Server settings. Some Googling turned up this thread in VMware Communities, which spells out the following fix:

  1. Edit /etc/vmware/webAccess/proxy.properties
  2. Change the following line:proxy.noCache = false…to:

    proxy.noCache = true

  3. Restart the vmware-mgmt service:
    /etc/init.d/vmware-mgmt restart

That’s it! You may need to refresh your browser one more time after this, but after completing these steps, you should now be prompted to login to VMware Infrastructure Web Access.

July 31, 2009

Joining the ACM – A Linux Sysadmin’s Perpective

Filed under: Linux,Systems Administration — Matt @ 9:07 pm

The ACM, or the Association of Computing Machinery describes itself as “the world’s largest educational and scientific computing society”. Until recently, I assumed that since I was out of academia, and focused more on things that sysadmins do, like developing, and implementing real-world solutions than the stuff of research papers, the ACM didn’t have much to offer me.

A contributor to this bias was the fact that I joined the ACM a few years ago while I was in college. I was working with a couple professors on a project that involved using Linux virtualization to teach networking concepts. Anyway, the reason I joined the ACM was that I was asked to give a presentation at an academic computing conference. As I recall, the two requirements for being a presenter were having a .edu email address (check), and ACM membership. I quickly signed up, and failed to investigate what benefits ACM membership would bring.

Fast forward to today. I spend a lot of time reading to keep up on current technologies, and while I am able to do most of this online, I still spend a lot of money each year buying books. A significant portion of these are published by O’Reilly, which writes a lot of excellent Linux, Unix, and development books. Cisco Press’ books make up another significant portion of my collection. Most of the networking products that I work with run either Linux or one of the BSDs, but I’m yet to find a publisher that consistently covers such a wide range of networking topics as well as Cisco Press does.

Many of these O’Reilly and Cisco Press books are available online through Safari. I was once a subscriber, and was happy with their service overall, but at $23/month, membership dues added up. This is where ACM membership comes in. For $99/year, they offer a number of benefits, including the one that I was most interested in – access to a large portion (600) of Safari’s collection of books. Restarting my ACM membership seemed like a no-brainer, given that I was about to spend $60 on one of the Cisco Press titles included in the collection.

I just joined, and taking a look at what else the ACM offers members, like what I see:

  • Access to 500 of Books24x7’s books. Looking over the list, I can see that this would be especially useful to those who are more involved in the Microsft and/or management side of things than I am. 🙂 Actually, there are a few Sybex books on that list that look interesting. I’ve been meaning to brush up on my Java and Oracle, and also see a number of books covering those topics. The Linux books on the list include:
    • Ubuntu Linux Bible
    • Professional Linux 10 Programming
    • Setting up LAMP; Getting Linux, Apache, MySQL, and PHP Working Together
    • Linux Firewalls: Attack Detection and Response with iptables, psad, and fwsnort
  • All 184 issues of the Linux Journal. If you’re not familiar with this magazine, it’s an excellent resource covering all things Linux.
  • Element K courses and simulators. I haven’t used these before, but see a course listed for Cisco’s BCMSN exam, which I’m scheduled to take in a few weeks. I’ll check it out.

I feel like I’ve just scratched the service. Even if I don’t find anything else in the membership benefits worth using, $99/year for access to this collection of information is a bargain for a sysadmin who’s serious about learning.

April 3, 2009

Installing Linux using a serial console

Filed under: Linux — Matt @ 3:22 am

Just a quick note on the command to use to start up a RHEL / CentOS 5.x install from the serial console. This can come in handy if you’re using a modem and serial port for out of band management, and the need to conduct a remote reinstall arises. These settings start up a console on ttys0 (Serial Port 1) with the standard 9600/8-N-1 settings.

linux console=ttyS0,9600n8

March 24, 2009

vsftpd's “500 OOPS: cannot change directory” error

Filed under: Linux — Matt @ 2:00 pm

I recently installed a vsftpd FTP server on a CentOS Linux 5.2 box. After changing the FTP user’s home directory, I received the following error message every time I attempted to login as ftp:

500 OOPS: cannot change directory
500 OOPS: child died

Permissions were setup correctly on the ftp user’s home directory, so I did some digging around, and discovered that there’s an SELinux setting that causes this problem. I didn’t want to turn SELinux off, so the solution was to run the following command, which enables access to the ftp user’s home directory.

setsebool -P ftp_home_dir

March 19, 2009

Resuming failed Firefox downloads

Filed under: Linux — Matt @ 9:45 am

Firefox’s download manager doesn’t have a built-in mechanism for resuming failed downloads. My Internet connection was cut off just long enough this morning for a Firefox download of an ISO image to fail. To resume the download, I used the wget command, which is built into most Linux distributions, and installable if you’re running OS X or Windows. If you’re running Windows you can download wget from GnuWin32. If you’re running OS X, you can install wget with DarwinPorts.

To resume the failed Firefox download, open up a terminal, change to the directory that the is located in, and issue the wget command with the -c option. The -c option tells wget to continue the failed Firefox download. For example:

cd Downloads
wget -c http://download.mozilla.org/failed-download

March 2, 2009

Bypass rm's “argument list too long” error message with xargs

Filed under: Linux — Tags: , , — Matt @ 3:19 pm

When using rm to delete a large number of files, you may come up against a kernel limitation which limits the length of arguments that can be sent to rm:

$ rm *

bash: /bin/rm: Argument list too long

This one-liner utilizes xargs to bypass this limitation:

ls | xargs rm

January 23, 2009

How to reconfigure CPAN

Filed under: Linux — Matt @ 12:29 am

I’m always forgetting the command that’s needed to start CPAN’s configuration wizard back up after its initial setup. To reconfigure CPAN, just execute the follow command from the CPAN prompt:

o conf init

January 6, 2009

Linksys PAP2T-NA Gizmo Settings

Filed under: Systems Administration — Matt @ 9:11 pm

Here are the settings that I used to get a Linksys PAP2T-NA working with Gizmo:

  1. Browse to the PAP2T-NA’s web page, for example http://192.168.111.100
  2. Click the PAP2T-NA’s “Admin Login” link
  3. Click on the “Line 1” tab
  4. Fill in the following three values, and hit submit:
    1. Proxy: proxy01.sipphone.com
    2. Display Name: Your Name
    3. User ID: Your Gizmo SIP number, for example 17471234567
    4. Password: Your Gizmo password
  5. Click the “Save Settings” button

That’s it! Your Linksys PAP2T-NA is now configured to use your Gizmo account.

October 16, 2008

Bypassing the “You use an internal update server. Abort.” message when upgrading from SLES 10 to SLES SP1

Filed under: Linux — Matt @ 4:47 pm

I’m currently performing an online upgrade from SLES 10 (SUSE Linux Enterprise Server 10) to SLES 10 SP2. While following Novell’s instructions on upgrading from SLES 10 to SLES SP1, I hit the error message below:

sles10-32bit:~ # switch-update-server
You use an internal update server. Abort.

The fix was to edit /usr/bin/switch-update-server , comment out the following lines, then run switch-update-server again.

# check if there is a old or new update server
#if ! echo "$CHECK_URIS" | grep -F "$NEW_SERVER_NAME" >/dev/null 2>&1 &&
# ! echo "$CHECK_URIS" | grep -F "$OLD_SERVER_NAME" >/dev/null 2>&1; then
# # no old and no new update server => not registered or use an internal mirror
# # no need to switch
# echo "You use an internal update server. Abort." >&2
# echo "You use an internal update server. Abort."
# exit 1
#fi

August 23, 2008

Enable the “Remember my password” checkbox for network shares in Windows XP Professional

Filed under: Systems Administration — Matt @ 6:12 pm

Windows XP Professional offers a Remember my password checkbox when mapping to a network drive, or other password protected network resource.
Unfortunately, once you’ve set a password, the Remember my password box disappears, so future username or password changes can result in repeated password prompts. Here’s how to clear your previously set username and password, and get the Remember my password checkbox back:

  1. Click Start -> Run
  2. Type in control userpasswords2, and press Enter
  3. Click on the Advanced tab
  4. Click the Manage Passwords button
  5. Select the server for which you wish to delete existing settings, then click the Remove button
  6. Click Close
  7. Click OK
  8. Logout of Windows XP, then back in
  9. Connect to the password protected server. You should now be prompted for your username and password, along with the previously missing Remember my password checkbox

The above may work in other version of Windows, but I haven’t tested this out. Please post a comment if you’ve been able to use this procedure to get the Remember my password box back under your Windows version!

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