Updating the default system editor - Debian

sudo update-alternatives --config editor

Then make your selection.

FIN

Change Directory and list contents in single command.

I find myself often changing to a directory and immediately performing an `ls`. This is partly habit and partly the fluid nature nature of the files I work on.  Anyway, you don't care about that...

Using an editor of your choosing open your .bashrc or .bash_profile and add the following lines:

# User defined functions
function cdl { cd $1 && echo $PWD && ll; }

Note: In the above I have aliased `ll` as ->  alias ll='ls -ASlh'
Note: You can name this whatever you choose, I just think `cdl` made sense.
Note: You can omit the echo $PWD if you don't care to see the directory path in the output. So you could do something as simple as:

# User defined functions
function cdl { cd $1 && ls; }

Save and close and then

bkarels@rev0:~$ source ~/.bashrc

Now you can use cdl (or whatever you've named it to change directory and immediately ls the contents.

Example:

bkarels@rev0:~$ cdl foo/

/home/bkarels/foo
total 328K
-rw-------   1 bkarels bkarels 156K Aug  8 09:39 sample0
-rw-------   1 bkarels bkarels 6.9K Aug  8 08:47 someFile27
-rw-r--r--   1 bkarels bkarels 4.1K Aug  7 12:07 sayWhat
drwx------   6 bkarels bkarels 4.0K Aug  8 07:37 killWindows.exe

The above example was done on Debian 7 (Wheezy) but should work on all flavors of *nix and OSX.

FIN

Quick & Dirty Add User to SUDOERs (*nix)

While there is near endless and very powerful ways to configure user permissions, you've just spun up a virtual machine using VMWare or Virtual Box and you want God permissions for your user so you're not always becoming root (and then forgetting that you're root). The following example is from CentOS 6.5. Since you can destroy a system if you muck up the sudoers file just using any old text editor is not recommended. Hence, we shall use visudo.

[myuser@machine ~]$ su -
Password:
[root@machine ~]# visudo

This will open your sudoers file for editing. visudo will protect you from some, but not nearly all mistakes. So, for this quick dirty example search for the following section:

## Allow root to run any commands anywhere
root ALL=(ALL) ALL

Then, add the following directly below it:

myuser ALL=(ALL) ALL

The end result should look like:

## Allow root to run any commands anywhere
root ALL=(ALL) ALL
myuser ALL=(ALL) ALL

NOTE: The above is separated by TABS so you would type it as follows:
myuser[TAB]ALL=(ALL)[TAB]ALL

Save & close (:wq) 

[root@machine ~]# exit
[myuser@machine ~]$ sudo someCommand

FIN

mkdir and cd to created directory with a single command - 11.04 Natty

Not a fan of having to cd to the directory you just created? You likely created it for a reason and 8 times out of 10 not need to cd to it immediately anyway. So, you do this:

user@machine:~$ mkdir -p /dir/needed/to/cd/to/immediately
user@machine:~$ cd /dir/needed/to/cd/to/immediately
user@machine:~$ pwd
/home/user/dir/needed/to/cd/to/immediately

Quick functional solution: Open ~/.bashrc (or .bash_profile) and add the following line:

function mkdircd () { mkdir -p "$@" && eval cd "\"\$$#\""; }

NOTE: You can name this function whatever you like, mkdircd just makes sense to me...

Source ~/.bashrc and now let's do this the easy way:

user@machine:~$ mkdircd dir/needed/to/go/to/immediately
user@machine:~/dir/needed/to/go/to/immediately$ pwd
/home/user/dir/needed/to/go/to/immediately

~Fin

"Remote" administration of Linux VirtualBox® Guest Virtual Machines

Sometimes you just need a sandbox of your very own. Oracle's VirtualBox has long offered a way to let you play with a guest OS on your host system - but what if you need to interact with the guest from your host? In my case I wanted to simulate a sharded MongoDB cluster that, to be a true simulation, required a minimum of three servers.

Here we will go over the process of setting up your virtual machine in such a way that you can "remote" administer it and connect to it like any server on your network. For this example I will be running and OS X host with a Ubuntu Server 10.10 guest.

1. Download and install Oracle VirtualBox® here.

2. With VirtualBox® installed, let's take a look at our network settings on the host machine with `ifconfig`. Here you will want to take note of the vboxnet0 address:



3. Add a new virtual machine using the Oracle VM VirtualBox Manager. Once the initial setup is complete select the new virtual machine can click on the network adapter to add a second:



4. Adapter #1 will be configured by default and does not need to be altered. Click on the tab for `Adapter 2`, enable, and configure as follows:



5. Click the green arrow in the VM Manger to start the new virtual machine and install the new guest. (the rest of this example assumes a guest of type Ubuntu Server 10.10 but should be very similar for all flavors of *nix.)

6. During the guest install be sure to select eth0 as the primary network adapter.



7. Also, to save the need to set up the OpenSSH Server later, you can elect to do so as part of the OS install.



8. Start up the new guest and login.

9. Configure eth1 by modifying /etc/network/interfaces Add the following lines:
(NOTE: The address below is made up from the VBoxnet0 address noted in Step 2 above. Since mine defaulted to 192.168.56.1 I was free to use any value beyond that as below.)

# Secondary network interface for VBox0
auto eth1
iface eth1 inet static
address 192.168.56.102
netmask 255.255.255.0

10. Save and close /etc/network/interfaces and bring up eth1 using:

sudo ifup eth1

Your terminal might look like this when done:



11. Open a terminal on your host machine and connect to your guest using SSH:



If all went well you should be connected via SSH to your guest system and be able to interact with it as you would any server on your network. So, let's fire up a remote MongoDB server on our guest and verify that we can reach the Http Interface for the instance.

Starting up mongod on port 27000 on mongo2 (Http Interface defaults to [port] + 1000 or 28000 in this case):



...and voilà! We are connected to our "remote" instance.



Fin

Using custom shell scripts on Linux & OSX

You need to create a custom shell script and would like to run it from anywhere on your system.

1. Create a `bin` directory to store your script.

machine:~ user$ mkdir ~/bin

For Linux users this will create /home/[user]/bin, for OSX you'll have /Users/[user]/bin. You could name this directory whatever you'd like, but bin seems fitting.

2. Modify .bashrc or .bash_profile to put `bin` on your path.

If you're comfortable with vi you can: (Alternatively use any text editor you are comfortable with)

machine:~ user$ vi ~/.bash_profile [OSX]
user@machine:~$ vi ~/.bashrc [Linux]

Either way, add the following line:

PATH=$PATH:$HOME/bin

3. Save and exit.

4. Source your file for it to take effect:

machine:~ user$ . ~/.bash_profile [OSX]
user@machine:~$ . ~/.bashrc [Linux]

5. Now you can drop a shell script into your bin directory and have executable from anywhere on your filesystem (don't forget to make it executable!)

Example:

Last login: Thu Mar 31 11:07:30 on ttys004
machine:~ user$ pwd
/Users/user
machine:~ user$ touch example
machine:~ user$ vi example
...

#!/bin/sh
echo "Somewhere in Russia a little girl is warming up with your max."

...
machine:~ user$ mv example ~/bin/
machine:~ user$ chmod +x ~/bin/example
machine:~ user$ ls -l ~/bin | grep example
-rwxr-xr-x 1 user staff 80 Mar 31 14:25 example
machine:~ user$ cd /tmp/
machine:tmp user$ example
Somewhere in Russia a little girl is warming up with your max.
machine:tmp user$

Fin

Lift weights - Lift spirits

Simple command line encryption

Works on OS X, Linux, anywhere with OpenSSL installed:
(NOTE: With OS X Lion breaking TrueCrypt - this is simple replacement that, in a way, simplifies things.)

To encrypt the file:

openssl des3 -salt -in infile.txt -out encryptedfile.txt

To decrypt the file:

openssl des3 -d -salt -in encryptedfile.txt -out normalfile.txt

The -a option, stores the encrypted file in base64 instead of binary.

To encrypt the file stored in base64:

openssl des3 -a -salt -in infile.txt -out encryptedfile.txt

To decrypt the file stored in base64:

openssl des3 -d -a -salt -in encryptedfile.txt -out normalfile.txt

To see a list of all available ciphers and other command information:

openssl -h

Other examples(notes to self...):
openssl des3 -salt -in rev27_*****_2010.zip -out rev27_*****_2010.zip.des3
openssl des3 -salt -in pf_*****_2010.zip -out pf_*****_2010.zip.des3

View output in console and write to file using tee - Mac OS X 10.6.4

Use tee to send output to the console and to a file:

machine:dir user$ ./some_program | tee output_file.txt

Executing the above command will display the output of some_program immediately in the console and write the same contents to output_file.txt.

I use this command mostly for diffs against svn, saves a step. Also, though I'm posting this as a Mac OS X terminal option, I first discovered this on Ubuntu 8.04 though I sure the history or this command is much older. I recall from the documentation to think of this in plumbing terms: Send your output down a pipe to a "T" essentially sending the same stream/flow to two different places.

~Fin

Recursive SVN Directory Removal - Ubuntu 9.10 Karmic

From time to time it can be handy to remove subversion references from code that is sitting on the file system. The following command will remove all '.svn' directories from the current directory on down:

user@machine:~/dev/sample1$ rm -rf `find . -type d -name .svn`

(Please note those are grave accent quotes - below the tilde on the key left of the one(1) key.)

This command should work for all flavours of Unix.

~Fin

Create a symbolic link - Ubuntu 9.10 Karmic

ln -s /path/to/real/file /path/to/non-existant/file

So you could do like:

user@machine:~/devtools/jdk$ ll
drwxr-xr-x 10 root root 4096 2010-01-12 11:11 jdk-1.6.0
user@machine:~/devtools/jdk$ ln -s jdk-1.6.0/ current
user@machine:~/devtools/jdk$ ll
lrwxrwxrwx 1 brad brad 10 2010-01-12 11:25 current -> jdk-1.6.0/
drwxr-xr-x 10 root root 4096 2010-01-12 11:11 jdk-1.6.0
user@machine:~/devtools/jdk$

~Fin

Start, stop, restart MySql - Ubuntu 9.04 Jaunty

user@machine:~$ sudo /etc/init.d/mysql [start, stop, restart]

~Fin

Reset root password for MySql 5.* - Ubuntu 9.04 Jaunty

user@computer:~$ sudo dpkg-reconfigure mysql-server-5.0

This will pop a "dialog" in your terminal and advise you to set a root password. Verify, tab to <OK> and try logging in again:

user@computer:~$ mysql -uroot -p<password_you_just_set>
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 29
Server version: 5.0.75-0ubuntu10.2 (Ubuntu)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql>

~Fin

Using Tabs in the terminal - Ubuntu 9.04 Jaunty

Using tabs in the terminal to avoid having several terminals opens saves space and time (how did I not know about this earlier!).

Open a terminal and create a new tab using:

<shift> + <ctrl> + T

To switch between tabs using the keyboard:

<ctrl> + <page down>
(Moves one tab right - will loop through all tabs from left to right.)

<ctrl> + <page up>
(Moves one tab left - will loop through all tabs from right to left.)

~Fin

shred a File - Ubuntu 9.04 Jaunty

Computer files containing sensitive information should also be 'shredded'. There is a command line utility on Linux systems called 'shred' that overwrites the file multiple times with random output. If you simply erase a file with 'rm', this only tells the operating system that this part of your hard disk is free for use, but the information still exists until that space is overwritten. Information from a file that has been deleted can still be recovered unless it has been 'shred', making it nearly impossible to recover.

The following command will shred a file, "zero" it (to hide shredding) and then remove it.

user@machine:~$ shred -zuv sensative.file

~Fin

Have more visual fun - Ubuntu 9.04 Jaunty

user@machine:~$ sudo apt-get install compizconfig-settings-manager

Then open in:
System --> Preferences --> CompizConfig Settings Manager

Then:

1. Draw fire on the desktop
2. Use the desktop cube
3. Animate maximize, minimize, and other actions.
4. Other fun stuff I've yet to play with! w00t!

~Fin

Find files larger than a given size in Linux - Ubuntu 9.04 Jaunty

Using the command line, you can search for files larger than a given file size using:

user@machine:~$ find /path/to/directory -type f -size +1024k

This will search for files larger than 1MB (1024k). Obviously you can adjust this number to suite your search requirements.

~Fin

How to Create & Extract tar.gz and tar.bz2 Files in Linux - Ubuntu 9.04 Jaunty

How to create a compressed tar.gz file from a folder or file in Linux?
In order to create a compressed tar.gz archive from a folder/file we need to run the following tar command:

tar czf new-tar-file-name.tar.gz file-or-folder-to-archive

Here is the command explanation:

* tar - the tar command.
* c - create new archive.
* z - compress the archive using gzip.
* f - use archive file.
* new-tar-file-name.tar.gz - the name of the tar.gz to create.
* file-or-folder-to-archive - the name of the folder we want to archive.

How to create a compressed tar.gz file from multiple files and folders in Linux?
In order to create a compressed tar.gz file from multiple files or/and folders we need to run the same tar command we used when we archived a single file/folder and to append the rest of the files/folders' names to it.

tar -czf new-tar-file-name.tar.gz file1 file2 folder1 folder2

How to extract a compressed tar.gz file in Linux?
tar -xzf tar-file-name.tar.gz

Here is the command explanation:

* tar - the tar command.
* x - extract the archive.
* z - uncompress the archive using gzip.
* f - use archive file.
* tar-file-name.tar.gz - the name of the tar.gz to extract.

The tar command will extract all the files/folders in the archive to the current directory.

How to extract a compressed tar.bz2 file in Linux?

Extracting tar.bz2 (bzip2 file) is very similar to the way you extract tar.gz file. Instead of using the -z flag you need to use the -j flag for the bzip2 format
tar -xjf tar-file-name.tar.gz

Here is the command explanation:

* tar - the tar command.
* x - extract the archive.
* j - filter the archive through bzip2
* f - use archive file.
* tar-file-name.tar.gz - the name of the tar.gz to create.

The tar command will extract all the files/folders in the archive to the current directory.

~Fin

Execute/install from a .bundle file - Ubuntu Linux 9.04 Jaunty

sudo sh fileName.bundle

~Fin

Show line numbers in VI - Ubuntu Linux 9.04 Jaunty/Mac OS X

Update - verified to work also with Mac OS X

From within VI
:set number

To make this behaviour the default:
user@machine:~$ cd ~
user@machine:~$ touch .exrc
user@machiner:~$ vi .exrc

Add the following line to the file:
set number
user@machine:~$ . .exrc
user@machine:~$ vi someTextFile.txt

Basically, if the file .exrc does not exist in your home directory create it.
Open .exrc for editing.
Add the line (w/o quotes) "set number"
Save .exrc
Source .exrc
Test to verify function.

Update (as I've had to look this up twice now...)
To turn off line numbers from withing VI
:set nonumber

~Fin

How to start, stop, & restart samba - Ubuntu Linux 9.04 Jaunty

sudo /ect/init.d/samba stop
sudo /ect/init.d/samba start
sudo /ect/init.d/samba restart

~Fin