Installing VirtualBox machine Additions on CentOS 5.1 - 5.3

For a few weeks now I have been creating a VirtualBox VM for a demo server. The purpose is to give our sales staff a way to bring our technology to the client and show them, in a live environment how our systems works, even if they don't have an Internet connection available.

I have been working on this system in a ridicously small screen for a little while now and finally got sick of it. I had tried installing the Virtual Machine additions before, but it failed for one reason or another. This time around I was determined to get everything up and running properly, so A) I wouldn't have to work on such a small screen and B) I could just move my mouse between the VM and my Desktop with out hitting a button.

Anyways, on to the meat of this, how to install the pre-requsite libraries and the Virtual Machine additons on CentOS. Now I just did this on a CentOS 5.3 install, but it has reportidly worked as far back as 5.1.

First you need to install the kernel sources and gcc, if you don't already have them.

yum isntall -y gcc
yum install -y kernel sources kernel-devel

Then you need to create a symbolic link to the kernel source:
ln -s /usr/src/kernels/2.6.18-92.1.18.el5-i686 /usr/src/linux

After this it is best to reboot the machine:
shutdown -r now

Once the machine has come back online you can mount the Guest additions ISO and install them via one of two commands depending on your architecture:

sh VBoxLinuxAdditions-x86.run

or
sh VBoxLinuxAddtions-amd64.run


After either of these commands are run you will have to once again reboot the Virtual Machine:
shutdown -r now

After the reboot you should be able to move the mouse between the VM and you Host OS without unlocking it and any of the other nifty features the Guest additions add.

Failed to modify password entry for user while adding user with smbpasswd

I was trying to create a user today in samba and was getting the error "Failed to modify password entry for user [USER]".

I read over the man pages for smbpasswd and saw that I needed to add the -n switch because this user will not have a password. So again I tried to add the user with "smbpasswd -a -n [USER]" and got the same error.

A quick Google search lead me to a newb mistake on my part... I didn't have the user I was trying to add in my UNIX password file. A quick "useradd [USER]" followed by the same "smbpasswd -a -n [USER]" and I was all set.

Granted there are other reasons why this process might fail, but for me this was the reason.

A simple file shredder for Windows

Working with sensitive data all day long you come to realize that what I download needs to be deleted securely, just as the paper copies need to destroyed securely.

I happened upon this script on Lifehacker a while ago, but I have been using it more and more lately.

First you will need to download sdelete from Microsoft. I copy this exe to the Windows directory on each machine as part of my install process.

The script if very simple:
@echo off
FOR %%F IN (%1 %2 %3 %4 %5 %6 %7 %8 %9 %10) DO sdelete -p 7 -s %%F

I save this as shred.cmd and place it in my C:\Scripts folder. It will take up to 10 files at a time and run sdelete with 7 passes on each file. Sdelete will also rename the file 26 times to obfuscate the file name.

About once a month I will run sdelete -p 3 -z to clean the free space on my PC and to make sure that any temp files I didn't shred are cleaned up. Now this won't obfuscate the file names at all, but the contents of the files are gone for good.

You can also place a short cut to the shred.cmd file into your Send To menu options and have an easy way to clean files from any folder.

Adding programs to the "Send To" menu

From time to time I write small scripts that accept Command line arguments. In the past I kept shortcuts to them on my desktop, but today I wanted to remove all icons from my desktop.

If you open up %APPDATA%\Microsoft\Windows\SendTo in Windows Explorer.

You see %APPDATA% is an environment variable that usually maps to something like C:\Documents and Settings\[YOUR USER PROFILE]\Application Data\ in Windows 2000/XP and "C:\Users\[YOUR USER PROFILE]\Application Data\" in Windows Vista.

Let's say you wanted to add an item to the Send To menu to shred files with sdelete. You could just drag a shortcut to the shred script this folder, or create a new shortcut.

This method should work for any application that allows you to open a file by using a command line argument.

mail command returns fseek Invalid argument, panic temporary file seek

Today I logged into one of our older servers, haven't logged into it for a while and saw that there was new mail (as always given the number of cron jobs running).

Below is the output of my command.

[root@server /]# mail 

"/var/spool/mail/root": 1832 messages 1777 new 1832 unread 

fseek: Invalid argument 

panic: temporary file seek

After a little bit of searching online I found two possible and simple solutions.

If you want to read the mail try using mutt instead of mail. It doesn't have a problem with the 2GB file size of the mail box that mail did.

If you don't care about the old stuff you can run:

rm -f /var/spool/mail/root

to remove the file and then

cat /dev/null > /var/spool/mail/root

to recreate a blank file.  

I ended up reading the mail I wanted and then blowing the file away.  But before I could recreate it there was already a new file with 62MB of mail in it.  

Excluding Directories from updatedb on CentOS 5

Running the updatedb command will update the slocate database.  However if you want to exclude certain directories for any reason, such as not wanting to include a huge NFS file store or something to that affect you have two options.

1) use the -e switch with a comma seperated list of directories to not index. (updatedb -e /Storage,/home)

2)edit the /etc/updatedb.conf file.

•  vi /etc/updatedb.conf
  
• find the PRUNEPATHS section and add the directories to the list seperated by spaces. (PRUNEPATHS = "/afs /media /net /sfs /tmp /udev /var/spool/cups /var/spool/squid /var/tmp /Storage /home")

Also you can read up on updatedb by reading the man pages.

man updatedb

error: can't create transaction lock on /var/lib/rpm/__db.000

I got the error message today while upgrading Webmin.  The fix for this is pretty simple:

rm -f /var/lib/rpm/__db.0*

rpm --rebuilddb

The first command clears out any of the files that will lock an RPM from running.  The second command rebuilds the RPM database.

Then I was able to install Webmin 1.470 from the RPM that I had downloaded with:

rpm -Uhv /Storage/rpmDownloads/webmin-1.470-1.noarch.rpm

memcached init.d statup scripts for CentOS 5.2.

While working to setup memcached on my CentOS servers I came across these scripts.  They are the typical startup, restart, shutdown, status scripts I am sure you are used to using.  

I found them on both http://www.dev411.com/wiki/Memcached_startup_files_for_Red_Hat_(RHEL) and http://www.vbseo.com/blogs/danny-bembibre/daemon-scripts-memcached-44/.  

Both sites have the same script contents but I feel that vbseo.com has the more complete instructions.

Please check your autoconf installation and the $PHP_AUTOCONFenvironment variable is set correctly and then rerun this script.

This is a very simple fix if you are running Redhat Enterprise / CentOS 5.2.  

yum install autoconf

I came across this while setting up memcache / memcached.  I had tried running phpize from the memcach-2.2.4 directory but was getting the error "Please check your autoconf installation and the $PHP_AUTOCONFenvironment variable is set correctly and then rerun this script."

Once I had autoconf installed I was able to finish the install process

./configure

make

make install

I know there are easier ways to do all of this on CentOS, but we are using a newer version of PHP (5.2.6) than came with CentOS (5.1.6), so using yum to install this would not have worked.