Updating the default system editor - Debian

sudo update-alternatives --config editor

Then make your selection.

FIN

Resize Logical Volumes within a Volume Group (LVM2 on Debian 7)

I'll refine this later, just need to capture what I had to do this morning...

OK, I needed room on `/` to accommodate mongoDB journaling files.  I have debian 7 (Wheezy) running in a virtual machine with a separate /home partition. 

To get the space I needed I planned to take 5Gb from /home and add it to /.

So, as root, show me my Physical Volume:

root@rev0:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda5
  VG Name               rev0
  PV Size               89.76 GiB / not usable 2.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              22978
  Free PE               0
  Allocated PE          22978
  PV UUID               KBuU17-GOD4-8ckZ-EaJG-aurI-9ufl-oeUCNy

Show me my Logical Volumes at a high level using lvs:

root@rev0:~# lvs
  LV     VG   Attr     LSize  Pool Origin Data%  Move Log Copy%  Convert
  home   rev0 -wi-ao-- 77.19g                                          
  root   rev0 -wi-ao--  4.31g                                          
  swap_1 rev0 -wi-ao--  3.25g

Reduce the size of my /home LV using lvreduce (-5G = reduce by 5Gb):
NOTE: the LV path (/dev/rev0/home) can be found with the lvdisplay command which is illustrated below.)

root@rev0:~# lvreduce -L-5G /dev/rev0/home
  WARNING: Reducing active and open logical volume to 72.19 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce home? [y/n]: y
  Reducing logical volume home to 72.19 GiB
  Logical volume home successfully resized

Now add the newly available disk to root (/) using lvextend (conversely +5G here means grow by 5Gb):

 root@rev0:~# lvextend -L+5G /dev/rev0/root
  Extending logical volume root to 14.31 GiB
  Logical volume root successfully resized

GOTCHA!  Now here's what got me the first go round, the LV has now increased in size but the file system there remains at it's previous size.  So we need to grow the file system to fit the LV using resize2fs:

root@rev0:~# resize2fs /dev/rev0/root
resize2fs 1.42.5 (29-Jul-2012)
Filesystem at /dev/rev0/root is mounted on /; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/rev0/root to 3751936 (4k) blocks.
The filesystem on /dev/rev0/root is now 3751936 blocks long.

And when this is all done we can see the 5Gb shift from home to root:

root@rev0:~# lvs
  LV     VG   Attr     LSize  Pool Origin Data%  Move Log Copy%  Convert
  home   rev0 -wi-ao-- 72.19g                                          
  root   rev0 -wi-ao-- 14.31g                                          
  swap_1 rev0 -wi-ao--  3.25g

Or the more verbose:

root@rev0:~# lvdisplay
  --- Logical volume ---
  LV Path                /dev/rev0/root
  LV Name                root
  VG Name                rev0
  LV UUID                PA6izC-GU9D-eG9C-Ji9v-8avn-u7ng-dsLlPc
  LV Write Access        read/write
  LV Creation host, time rev0, 2014-08-07 07:40:00 -0500
  LV Status              available
  # open                 1
  LV Size                14.31 GiB
  Current LE             3664
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:0
  
  --- Logical volume ---
  LV Path                /dev/rev0/swap_1
  ***Swap omitted here***
  --- Logical volume ---
  LV Path                /dev/rev0/home
  LV Name                home
  VG Name                rev0
  LV UUID                0omdas-WNXb-17Sc-cfpZ-gRV0-i2G5-tHPV7L
  LV Write Access        read/write
  LV Creation host, time rev0, 2014-08-07 07:40:00 -0500
  LV Status              available
  # open                 1
  LV Size                72.19 GiB
  Current LE             18481
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:2

And now I have sufficient space on root for my journaling files.  Again, this was done fast and in a pinch, but it got the job done and may help others in a similar circumstance...

This should work for all flavors of *nix set up with LVM2.

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

Connect to SMB share with terminal - Fedora20

The non-gui way to connect to your SMB share. There is likely 1000 small variations of how to do this, but this is a very simple method to get you on to the path to bigger, better, cooler...

From a terminal:
[user@localhost user] $ cd /mnt
[user@localhost mnt] $ sudo mkdir shareExample
[user@localhost mnt] $ sudo mount -o username=user //theShareLocation/shareName /mnt/shareExample/
You will likely be prompted for your passwd...
[user@localhost mnt] $ cd /mnt/shareExample
[user@localhost shareExample] $ look around, do stuff...

NOTE: If you're accessing a SMB share on windows you will like need to connect using:
[user@localhost mnt]$ sudo mount -t smbfs -o username=username //theShareLocation/shareName /mnt/shareExample/

...and when you're done:
[user@localhost mnt]$ sudo umount /mnt/shareExample

This should work on all flavors of *nix, done here on Fedora20 as that is what I'm using at the moment.

FIN

Set tabstop in VI - Mac OSX

From within VI

(Assuming you would like to use four spaces for your tabs)
:set tabstop=4

To make this behaviour the default:

user@machine:~$ cd ~
(if ~/.exrc does not exist, create it.  Otherwise skip to next cmd.)
user@machine:~$ touch .exrc
user@machiner:~$ vi .exrc

Add the following line to the file:
set tabstop=4


Save and close .exrc

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 tabstop=4"
Save .exrc
Source .exrc
Test to verify function.

This should also work in most flavors of *nix.

~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

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