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

Generate SHA hash - OSX

I'll have to clean this post up later, but just to get this down.  Pulled the new Fedora 18 XFCE spin from the torrent and needed to verify it with the provided SHA256 hash.

At it's most basic:

computer:directory user$ shasum <filename>
<some_hash> <filename>

In the case below I needed a SHA256 hash so the -a arg was necessary:

computer:directory user$ shasum -a256 <filename>

<some_256_hash> <filename>

So, here is what I did - some content removed for brevity(...):

berlin:tmp bkarels$ cat Fedora-18-x86_64-Spins-CHECKSUM
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
...
95a75c...29dd6e *Fedora-18-x86_64-Live-XFCE.iso
berlin:tmp bkarels$ shasum -a256 Fedora-18-x86_64-Live-XFCE.iso
95a75c...29dd6e  Fedora-18-x86_64-Live-XFCE.iso

Checking the hash against a provided list was not as clear from the man pages.  In brief you need to use the output of a shasum as input to shasum -c.  Here you need only find 'OK' vs. relying on your human ability to visually compare hashes on a terminal.

Basic:

computer:directory user$ shasum -a 256 <filename> | shasum -c <CHECKSUM_FILE>
blah blah blah output: OK

Example:

berlin:tmp bkarels$ shasum -a 256 Fedora-18-x86_64-Live-XFCE.iso | shasum -c Fedora-18-x86_64-Spins-CHECKSUM
...
shasum: Fedora-18-x86_64-Live-Scientific-KDE.iso: No such file or directory
Fedora-18-x86_64-Live-Scientific-KDE.iso: FAILED open or read
shasum: Fedora-18-x86_64-Live-Security.iso: No such file or directory
Fedora-18-x86_64-Live-Security.iso: FAILED open or read
shasum: Fedora-18-x86_64-Live-SoaS.iso: No such file or directory
Fedora-18-x86_64-Live-SoaS.iso: FAILED open or read
Fedora-18-x86_64-Live-XFCE.iso: OKshasum: WARNING: 7 of 8 listed files could not be read

Fin.

NOTE: For clarity, here is the entire contents of the example file Fedora-18-x86_64-Spins-CHECKSUM:

berlin:tmp bkarels$ cat Fedora-18-x86_64-Spins-CHECKSUM
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
3684ae2814c7e54b4f66f0411a385846533e40f107d7fff4e331c2f547951ec2 *Fedora-18-x86_64-Live-Design-suite.iso
b11da64d527e333e2160cbf5fde49f89205f932d48fa7c01690232fc1b0cacfa *Fedora-18-x86_64-Live-Electronic-Lab.iso
ea34f626488623a1f84b2041df9c65468357bfdb878f034392da16f6c9d05264 *Fedora-18-x86_64-Live-LXDE.iso
8700aa64a6485e338b3d9aa419ecadc0c87884c77203a35c6e1847147a4dca06 *Fedora-18-x86_64-Live-Robotics.iso
3bb90d115daf6f0d2279cd5a669fb265c090cb6e88125424ae960a980f9ba50d *Fedora-18-x86_64-Live-Scientific-KDE.iso
7802a1c024f9471fba90724f53c0d95045acd76c3c4346b467cb53f5608248a9 *Fedora-18-x86_64-Live-Security.iso
736e8dd36de4207fe899648299abb6b3220fd1d1bcb48b8bf712d01d2ec02bf5 *Fedora-18-x86_64-Live-SoaS.iso
95a75c334ce82b33f1a5d81eab196600e40c7933fd5f7bfa8e6ed9534529dd6e *Fedora-18-x86_64-Live-XFCE.iso
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)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=/hTc
-----END PGP SIGNATURE-----

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