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Change the color and format of the Bash prompt

General Mills — Sun, 31 Jan 2010 04:57:23 +0000

Recently I got bored with the standard prompts and colors of the Bash shell in Linux, and decided to tweak them a bit. What I decided to do was to make the root user account have a red prompt, mainly so I wouldn’t forget to log out once I was done and also to distinguish it from normal user accounts.

Editing the Bash Prompt

In order to change the color of the bash prompt, you need to edit the PS1 environment variable. You can do this by typing the following in the bash shell:

export PS1="\e[31;1m[\u@\h \@ \W]# \e[0m"

This will temporarily change the color of the bash prompt to red, and some other parts of the prompt as well.

Here is a basic breakdown of each part of the command:

The export PS1= is telling the shell that you are changing the PS1 variable

The \e[31;1m controls what foreground and background the prompt will have. 31 = Red foreground, 1 = black background.

The "[\u@\h \@ \W]#" means “your username”@”hostname” “localtime” “working directory”.

Making PS1 Environment Variable changes Permanent

If you want to make the changes permanent, you will have to append this line of code to the end of your “.bashrc” file in your home directory. You can do this with by editing the .bashrc file with any text editor in linux (nano, vi, vim, gedit) and manually add in the following line export PS1="\e[31;1m[\u@\h \@ \W]# \e[0m" or this way:

1. Put export PS1="\e[31;1m[\u@\h \@ \W]# \e[0m" into a text file called "filenamehere"
2. Then type the following command:

cat filenamehere >> ~.bashrc

3. Then type exit in the terminal
4. Open up a new terminal and you then should see the changes to the bash prompt.

This effectively uses cat to pint the export PS1 command to standard output in the shell, then with the append operator ">>" it will redirect the export PS1 command and add it to the end of the .bashrc file. It's a fun and simple shell script! CAUTION!! Make sure you use the append operator ">>" and NOT the redirection ">" operator which will delete everything in the .bashrc file and replace it with what ever you redirected.

Reverse changes to PS1 Environment Variable
If you ever want to reverse the changes you have made to your PS1 environment variable, do the following:

1. Open a new terminal window
2. Type "vim .bashrc"
3. Use the arrow keys on the keyboard to scroll down to where it has the "Export PS1=" line.
4. Press the letter "d" twice on the keyboard to delete the whole line.
5. Press escape
6. press ":"
7. after the colon, type "qw" for quit and write. This will quit vim and save the file.
8. Exit the terminal
9. The next time you open a terminal for that user, you will have the default PS1 settings again.

If you would like to get more details and info about editing PS1 environment variables, visit the site in the references section below. It has a wealth of info on the subject. Enjoy!!

References:
http://www.funtoo.org/en/articles/linux/tips/prompt/

How to prevent yourself from accidentally deleting files in Unix/Linux Everyone at some point has faced that horrible moment when...

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Check if a certain user is logged on the Terminal Server using Powershell

General Mills — Mon, 28 Dec 2009 19:52:58 +0000

Just recently I have been developing a Powershell script to determine if a specific user on a Windows Terminal Server is logged in or not. If the user happens to not be logged in, It will e-mail a message to me and another co-worker to log that user in immediately.

It basically uses the quser command to get a list of the currently logged in users on the terminal server and stores that info into the variable $nwt. I then setup a if statement to see if it matches “nwt” which is the username I want to make sure is logged in at all times. If it does not find the string nwt in the $nwt variable, it will then send an e-mail to myself and a co-worker notifying us that he is not logged in. This is possible via the “System.Net.Mail” .net object in the .net framework. Here is a site with more information on the System.Net.Mail object, that helped me add a CC address to the e-mail, here is the link: systemnetmail.com. And that’s really all there is too it!

So far the script has been a success, since it has alerted us as to when this critical user account logs out so we can quickly log him back in. (We have some software that needs this specific user account to run properly.. it’s really crappy software..)

Below is the code:
——————————————————————-


$nwt = invoke-expression -Command "quser nwt"
$date = date
if($nwt -is [Array]){
if($nwt[1] -match "nwt"){
write-host "--> NWT is logged in!"
echo "--> NWT is logged in! [ $date ]" > ./nwt.log
}
}else{
write-host "--> [ Problem ] NWT is not logged in!"
$emailFrom = "administrator@example.com"
$emailTo = "youremail@example.com"
$subject = "NWT is not logged in"
$body = "
The NWT user account is not logged in on Termserver.  This was detected at:[ $date ]"$smtpServer = "mail.example.local"
$msg = new-object System.Net.Mail.MailMessage $emailFrom, $emailTo,
$subject, $body
$msg.CC.Add("co-worker@example.com")
$smtp = new-object Net.Mail.SmtpClient($smtpServer)
$smtp.Send($msg)
}

——————————————————————-

Powershell built-in GUI Editor!! Many of you have probably been on the look for...

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Windows – No Disk

General Mills — Fri, 11 Dec 2009 15:41:48 +0000

The other day a client calls up and says she keeps getting a “Windows – No Disk” window, that will not go away no matter how many times she closes it. I then asked when did this problem appear, in which she replied “after I pulled out the USB Flash Drive”. So at this point I was thinking that some files she was working on, wanted to save themselves to the usb flash drive and could not since the drive was not present, thus causing the annoying “No Disk” error. I then instructed her to save her work elsewhere on the hard drive and restart her workstation. Unfortunately however, after she restarted her workstation and logged in the error continued to pop up!

Since the restart didn’t solve the issue, I knew it was time pull out my best tool in the shed “Google Search”. After a couple google searches and a couple forums, I found out that the reason for this error is due to a usb driver that became corrupted during installation. The solution is to uninstall the usb drivers and reinstall them.

Once I had uninstalled all the usb drivers in Computer Management and restarted the workstation, the “Windows – No Disk” error appeared no more. Mere mortals can only guess why the usb driver became corrupted in Windows, but thanks to google and a post on technet this XP annoyance was solved!

References:

http://social.technet.microsoft.com/Forums/en/itprovistahardware/thread/d5f38918-d11b-45c4-861d-b53aa3dbdaed

NTBACKUP error – “End of Media encountered while backing up to non-removable media.” Today I was investigating why some ntbackup jobs were failing...

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NTBACKUP error – “End of Media encountered while backing up to non-removable media.”

General Mills — Fri, 13 Nov 2009 22:44:13 +0000

Today I was investigating why some ntbackup jobs were failing on a remote server, and came across this error message in the logs : “End of Media encountered while backup up to non-removable media”. So I googled the error, and came up with a couple forums talking about how backups being saved to tape drives get this error when the tape runs out of space. In my situation however, I was not using a tape drive for the backups, I was using an external hard drive.

Below is a screenshot of the NTBACKUP log

As you can see in the NTBACKUP log, when it tried to backup the files to the external hard drive it encountered the “End of Media” error.

So at this point I was hitting my head against the wall wondering why in the *(#$ is this happening!!? The external hard drive had plenty of free space for the backups, it just didn’t make any sense!! As a usual Sysadmin response I decided to dig dipper into the issue. After thinking it though a bit, I had some inspiration to check “Computer Management” and take a look at the partition and filesystem setup of the external hard drive. Below is a screenshot of what I discovered in Computer Management:

If you look volume E: in the top right, under filesystem it reads “fat32″! Once I saw that it occurred to me that the backups were failing because they exceeded the 4GB file size limit of the fat32 filesystem. Sure enough after checking the backup sizes It was just barely over 4GB which would explain why NTBACKUP reported that the disk was out of space. After discovering the true cause behind the failing backups, I backed-up all the data on the Western Digital MyBook, reformatted it with NTFS, and transferred all the data back onto the external drive. That effectively solved the issue and allowed the customer to continue to backup the server without buying any additional hardware.

It just comes to show that most problems are simple to fix and easy to overlook.

References:

http://www.experts-exchange.com/Storage/Misc/Q_20710438.html

http://en.wikipedia.org/wiki/File_Allocation_Table

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How to prevent yourself from accidentally deleting files in Unix/Linux

General Mills — Mon, 09 Nov 2009 23:36:37 +0000

Everyone at some point has faced that horrible moment when you realize that you just deleted a critical file, and start scrambling to find ways to recover it before it is too late. If you haven’t faced this situation yet, you are the lucky few who have been spared from this horrible experience so far. Just the other day, I found a really creative solution in Linux that will prevent you from accidentally deleting files by mistake. It’s actually not that complicated either, and I am sure you will be using this technique to protect your most valuable files after your through reading my how-to.

Step 1 – Choose a Directory

As you can see, I have created a directory called “test” and have created a ton of empty files and directories for testing purposes. It was fun writing the Perl script to create all those “crap” files.

Step 2 – Create a empty file call “-i” in the chosen directory

To do this simply use the touch command to create the empty file “-i”, as such: “touch ./-i”

Step 3 – Verify that “-i” exists in the current directory

To make sure “-i” was created successfully, list the directory contents by invoking the “ls” command as show above. Once you do that you will notice a new file called “-i” listed in the current directory.

Step 4 – Try to delete the files in the current directory

Try deleting all of them at once by using “rm *”.

WARNING – make sure you have the “-i” the the directory before you try to remove any files! Without the “-i” file there will be nothing to stop the rm command from removing your precious files!!

Below is a screenshot of what should happen when you try to delete any file in that directory.

Did you notice what happened? When we tried to delete any file in that directory, It would prompt us to confirm if we really wanted to delete each file. This happens because the “-i” file is immediately interpreted by the Unix/Linux command line as a option for the “rm” command, which prompts before deleting a file. If you man rm and look through the man page you will find the following entry:

  -i, --interactive
	      prompt before any removal

So that is the magic behind creating the empty “-i” file and how it helps prevent you from deleting file by mistake. Now don’t forget that if you use the rm -f command, it will delete the file no matter what!! That’s why it’s called the FORCE option!

Use this technique to your advantage and spread the word!

Understanding Unix/Linux Load Averages I was looking at some linux server the other day,...

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Understanding Unix/Linux Load Averages

General Mills — Wed, 07 Oct 2009 18:23:39 +0000

I was looking at some linux server the other day, and was taking a look of the load averages using the “top” command. After staring at the load averages for a while, I thought to myself ‘What does that mean exactly?” and “How do they get those numbers?”. Well after some research I have found out that the load average is not a % of cpu usage, but is a representation of the load on the CPU by processes waiting for their time to use the CPU.

Below is a screenshot of the top command for reference. Notice in the top right are the load averages “1.23″ 1.17″ “1.05″. The first load average is for 1 minute, the middle is for 5 minutes, and the last one is for 15 minutes.

Now the important thing to remember about Unix/Linux load averages is that it is not a % of cpu usage, but how many processes are waiting to use the cpu. The higher the load average, the more load the server in under. Right about now you are probably wondering ” well what is a normal load average?” or “What is a high load average?”, the easiest way to determine if your load average is normal or high is to look at it in the following way:

CPU Cores	Normal Load Average
1	1.00
2	2.00
3	3.00
4	4.00
8	8.00
16	16.00

As you can see a normal load average for a single core cpu is 1.00 while a dual core cpu can handle a load average of 2.00. If it helps you out, you can think of 1.00 to be %100 for a single core and 2.00 be %100 for a dual core, and so on.

Above is a screenshot of top showing each individual cores ultilization. This is an 8 core cpu, so it’s normal load average is 8.00. You can see this output in top by pressing “1″ on the keyboard. Also, if you were wondering how I got top to display different colors, just press “z” on the keyboard.

The key thing to remember is that load averages in Unix/Linux are not % for cpu utilization, it is merely a representation of how many processes are waiting for their turn to use the processor.

References
http://www.linuxjournal.com/article/9001

http://blog.raamdev.com/2008/11/22/understanding-the-linux-load-averages

How to prevent yourself from accidentally deleting files in Unix/Linux Everyone at some point has faced that horrible moment when...
Change the color and format of the Bash prompt Recently I got bored with the standard prompts and colors...

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Powershell built-in GUI Editor!!

General Mills — Mon, 05 Oct 2009 21:54:28 +0000

Many of you have probably been on the look for a gui editor for the new windows powershell, well look no more! Microsoft has included a built-in gui editor for powershell (I didn’t even know until now), and all you need to do to run it is follow one of the 2 ways below.

Method 1

1. Click Start
2. Type “Powershell ise” and hit enter
3. The Powershell integrated scripting environment will then start!

Method 2

1. Open powershell
2. In the console type: “powershell_ise.exe”
3. Hit enter.

Below are some screenshots for reference:

Below is a screenshot of what the Powershell ISE looks like. Check it out!

The powershell gui editor basically works like this: The top area is your script editor, the middle area is where you will see the output/results of your powershell script and commands. The bottom area is where you can enter powershell commands as if you were on the powershell command prompt.

Once you start using it, I am sure you will see a increase in productivity while creating/testing scripts. This is because it allows you to edit a script, run it, see it’s output, and even run commands as if you were at the command prompt. It’s streamlined everything you could want or need into one program! +1 point for Microsoft! (we’ll see how long that lasts lol).

Well what are you waiting for? Lets get scripting!

Powershell Download Links

1. Powershell 2.0 CTP

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Unattended FTP script to download files

General Mills — Sun, 30 Aug 2009 04:49:50 +0000

Looks like I also found a nice quick way to download files off my webserver using a ftp script. It’s so simple that I don’t know why I didn’t even think of it before! Before I had this script, I had to manually download my sysadmin-tools from my website onto the remote servers I was doing maintenance on that particular day. That took about 3-5 minutes each time I had to download the tools I had in a zip file on my webserver, which as you can imagine get really repetitive and annoying after a while. So after about the 50th time downloading the sysadmin-tools, I decided to automate it!

This is how I approached creating the script:

1. It has to work out of the box with Windows (I administer and maintain Windows Server 2003 boxes)

2. It had to connect to my webserver using my username and password

3. It had to change directories on the server to the download directory

4. K.I.S.S (keep it simple stupid!)

Decisions:

After reviewing the script requirements, I decided to write a simple batch script using the built in FTP command in windows. I didn’t know windows had a built in FTP command to tell you the truth until I starting writing the script.

Unattended FTP Script:

Below are the contents of the batch file:

@echo off

ftp -s:ftpscript.txt

Below are the contents of the ftpscript.txt file:

open
yourserver.com
username
password
cd “/public_html/yourdownloadfolder”
binary
get “sysadmin-tools.zip” “C:\Users\username\Desktop\sysadmin-tools.zip”
quit

Explanation:

It’s pretty straightforward, the batch file using the ftp command to start the built-in ftp program in windows. After that the batch script calls the “ftpscript.txt” file to supply the ftp command to execute. In the ftpscript.txt file it basically says to connect to a server, enters a username and password, then changes directories to the directory that contains the file you wish to download, switches the FTP mode to binary so it will download the .zip file correctly, downloads the file to somewhere on my Desktop, and finally quits FTP.

FTP Modes:

Make sure you are downloading in the right FTP mode!! I was getting corrupted files at first when I was making the script because I was downloading the .zip file in the wrong mode. Once I changed to binary it downloaded successfully without any corruption issues.

Text files (html, php, css, java) — use text mode
Multimedia files (images, audio, video) — use binary mode
Programs (.exe, .class, .jar, .swf) — use binary mode

References:
http://www.robvanderwoude.com/ftp.php
http://www.bluehostforum.com/showthread.php?t=9311

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Using scp with spaces in the file path

General Mills — Fri, 28 Aug 2009 16:24:14 +0000

I just recently learned how to upload a file from my linux box to my webserver using scp the other day. Normally its pretty straightforward to use scp to upload or download a file to a server, however I was having the hardest time uploading this one file that had spaces in the file path.

Here is what it looked like:

scp -r /home/username/Desktop/Sysadmin\ Tools/sysadmin-tools.zip user@website.com:public_html/somefolder/

When i would run this command, the following error would be displayed:

zip warning: name not matched: /home/username/Desktop/Sysadmin
zip warning: name not matched: Tools/*

As you can see, it was breaking up the file path at the space in “Sysadmin Tools” folder, and breaking it up into different arguments. The solution to this problem is to do the following:

Solution:

scp -r /home/username/Desktop/Sysadmin\\ Tools/sysadmin-tools.zip user@website.com:public_html/somefolder/

All I needed to add was an extra “\” backspace character after “Sysadmin”. This is because when the file is uploaded to the remote server, the “\” escape character will disappear (I am not sure why), and will cause this kind of error. However if you double escape the space “\\”, the first escape character will be removed but the second will remain, thus keeping the correct file path.

References:

http://www.thingy-ma-jig.co.uk/blog/14-05-2007/how-to-scp-a-path-with-spaces

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Shutdown script did not shutdown the sever! Exit Code 0x4f7

General Mills — Tue, 18 Aug 2009 17:22:02 +0000

Well recently a shutdown script that I wrote did not shutdown a server successfully for some odd reason. The script looks like the following:

shutdown -r -t 20 -c “Shutting Down to Install Windows Updates”

So until now this script has been working flawlessly on multiple servers. I’ve been able to schedule automatic reboots of remote servers easily using this script in combination with windows scheduled tasks as well. It comes in handy when you need to reboot the server at a specific time, such as 5:25PM or 1:26AM, which is great for me since I do a lot of remote server maintenance and do not have physical access to these servers.

Anyway, after trying to reboot this one server it gave me a exit code of (0x47f) which showed up in the scheduled tasks log.

After Looking up the exit code, I found a website that directed me to convert 47f to decimal and enter the decimal value “net helmsg” in the command line. The command I entered was “net helpmsg 1271″, which gave me the following answer: “The machine is locked and can not be shut down without the force option”.

Well isn’t that great! A error code that is easily understandable from Microsoft!

The solution to this problem was to edit my script to include the force option. Here is the updated script below:

shutdown -r -f -t 20 -c “Shutting Down to Install Windows Updates”

And that should do the trick.

References:

http://www.tech-archive.net/Archive/Windows/microsoft.public.windows.terminal_services/2006-08/msg00331.html

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