Convert MP4 to MKV

My Blue Ray Player does not play .mp4 files (x264)

To convert .mp4 files  to .mkv using ffmpeg
sudo yum install ffmpeg    (To install ffmpeg)

Then use the following command

ffmpeg -i filename.mp4 -vcodec ffv1 -acodec pcm_s16le filename.mkv

Upgrading Java

When ever you upgrade Java, the old version is always left on the server and is still in use. You will have to do the following to activate and use the new version.
in this example I am upgrading from Java 1.4 to 1.6
if java is available in your repository type 
yum update java or if you have the rpm
type rpm -Uvh java-version_of_yourJava.i386.rpm 
Although upgrade option is used in both instances, java is not actually upgraded. Just the new version is  installed alongside your current version.

You need to use the alternatives system to use the new version. here's how. type alternatives --config java 
The alternatives system maintains symbolic links determining default commands. Our new version of java is installed under
 /usr/java/jdk1.6.0_26 (so the path of java binary is /usr/java/jdk1.6.0_26/bin/java. I’ll add this as the default for Java:

type 

alternatives --config java 
You should receive output similar to the following:


There is 1 program which provide 'java'.

  Selection    Command
-----------------------------------------------
*  1           /usr/lib/jvm/jre-1.4.2-gcj/bin/java

Enter to keep the current selection[+], or type selection number: 


As you can see the new version of Java is not only not being used, but there is no mention of it in the alternatives system.
So we need to add it to the alternatives system to be able to use it. heres how. type 
alternatives --install /usr/bin/java java /usr/java/jdk1.6.0_43/bin/java 1 

The syntax of alternatives is as following 
-- install /path_to_symlink program_name /path_to_program priority

Once done if you type
alternatives --config java 
You should now get the following 


There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
*  1           /usr/lib/jvm/jre-1.4.2-gcj/bin/java
 + 2           /usr/java/jdk1.6.0_43/bin/java

Enter to keep the current selection[+], or type selection number: 

Simply select the version that you want to use as the default version.
Select 2 to use the new 1.6 version.
You can switch between versions this way and change back to the old version if you need to.

2 Way Synchronization with Unison

2 Way directory Synchronization

I found unison is a better option than rsync if the files in both locations frequently change, or if you want to synchronise between more than 2 locations. and you need to keep all locations synchronised.

yum install unison 
on all machines that you want to synchronise between.

for password-less sync make sure you setup ssh private/public key
as described in this previous post ssh public/private key

create a file sync.sh

vim sync.sh

copy and paste the following into your file


#!/bin/bash
# set paths / dirs
_paths="/home/cgerada/directory_to_sync"

# binary file name
_unison=/usr/bin/unison

# server names 
# sync local +server1 with server2 and server3
_rserver="server1.clive.com server2.clive.com server3.clive.com"

# sync it
for r in ${_rserver}
do
        for p in ${_paths}
        do
                ${_unison} -batch -force newer -times "${p}"  "ssh://${r}/${p}"
        done
done

save the file and give it execute rights

chmod + x sync.sh

to run the script on a cronjob every half an hour and output details into a log file

crontab -e

and add the following

*/30 * * * * /path/to/sync.sh &>/var/log/sync.sh.log

save and you are done.

~                                                                          
~                                                  

Chrooted SFTP

This will chroot (restrict)
all sftp users to their home directory

on your SFTP server type

group add sftpusers

vim /etc/ssh/sshd-config

comment out

#Subsystem       sftp    /usr/libexec/openssh/sftp-server

add

Subsystem       sftp    internal-sftp

You want to put only certain users (i.e users who belongs to sftpusers group) in the chroot jail environment. Add the following lines at the end of /etc/ssh/sshd_config

Match Group sftpusers

        ChrootDirectory %h

        ForceCommand internal-sftp

Match Group sftpusers – This indicates that the following lines will be matched only for users who belong to group sftpusers

ChrootDirectory /sftp/%h – This is the path that will be used for chroot after the user is authenticated. %h indicates the users home directory. So, for john, this will be /home/john.

ForceCommand internal-sftp – This forces the execution of the internal-sftp and ignores any command that are mentioned in the ~/.ssh/rc file.

next either add new users to your system or you can add existing users to the system

user add john mary clive

Add all sftp users to the sftp group by editing your 

/etc/group file  

sftpusers:x:501:john,mary,clive

Make sure users cannot login using ssh, do this by editing /etc/passwd

vim /etc/passwd

and changing /bin/bash to /bin/nologin of each SFTP user

From

john:x:500:500::/home/john:/bin/bash

To

john:x:500:500::/home/john:/bin/nologin

next 

chmod -R 755 /home/john

then you must set the following ownership to the users home directory

chown -R root:sftpusers /home/john

restart sshd

/etc/init.d/sshd restart

you can now sftp into your server and the sftp users will be restricted to their /home folder only.

                   

                                                                                                                                                

~                                                                                                                                                                 

Encrypting existin Swap Redhat / CentOS

yum install cryptsetup

Switch off swap

swapon -a

comment out existing swap partition is /etc/fstab

#/dev/mapper/VolGroup00-swap swap  

Wipe swap partition

dd if=/dev/zero of=/dev/mapper/VolGroup00-swap

add the swap partition to /etc/crypttab

If it is not already created, create the /etc/crypttab file. Add an entry to /etc/crypttab file. .


swap /dev/mapper/VolGroup00-swap /dev/urandom swap



Add the following entry to  /etc/fstab file.


/dev/mapper/swap none swap defaults 0 0


The next time you boot the system and the /etc/rs.sysinit script executes, it creates a raw dm-crypt device with a random key and formats it as a swap device. During /etc/fstab processing, the swap device is activated.
Reboot the system.
Verify that the swap space is encrypted.
swapon -s
You should see a new entry for the added swap file system. You can see it listed below in the second entry, in our example.
swapon -s


Filename Type Size Used Priority
/dev/dm-2                               partition 2064376 580 -1


Voila. your swap partition has been encrypted

mount remote directories over SSH using SSHFS

When you need to mount a remote directory securely
use SSHFS which is a much easier quicker option than trying to tunnel NFS over an ssh tunnel.

SSHS is quick , easy and secure.

yum install fuse-sshfs

If not done already you will wan't to create your private and public encryption keys and put your public key on the server who's directory you want to mount, so that you will have a password less connection
ssh-keygen to create the keys

leave passphrase blank

then to copy your public key to the server type
ssh-copy-id -i .ssh/id_rsa.pub user@remoteserver

Now, lets say there is some directory /mnt/dir/ on the remote system user@remoteserver and we want to mount it on our /localfolder directory. This is how we do it using sshfs.

type
sudo sshfs user@remoteserver:/mnt/dir /localfolder

Thats it. done.

and to unmount type

fusermount -u /localfolder/

If you want the directory to be available after a reboot

You could just put sudo sshfs user@remote:/mnt/dir /localfolder
in to your /etc/rc.local file

or if you prefer to use /etc/fstab then add the following line to your /etc/fstab file

sshfs#user@remoteserver:/mnt/dir /localfolder fuse    comment=sshfs,noauto,users,exec,uid=1000,gid=1000,allow_other,reconnect,transform_symlinks,BatchMode=yes

Dealing with Vcard meeting requests in Mutt

Receiving Vcard Meeting requests that have been generated in Microsoft exchange or MS outlook
arrives in to your Mutt inbox, as an illegible mess of text that is difficult to make heads or tails out of

To configure your mutt to play nicely with Vcard meeting requests do the following.
.
First install the following (If they are not already installed)

yum install perl
yum install perl-devel
yum install perl-Data-ICal
yum install perl-Text-Autoformat

or use apt-get install if your distribution is Debian based

Then edit your .muttrc and add in the following lines

alternative_order text/calendar
This tells Mutt to display the text/calendar part in preference to the text/plain part.

color index black yellow "~b text/calendar"
this shows all meeting requests as black on yellow
change the colours to which ever you would prefer

The final step is to decode the vCalendar text into something that’s a bit more readable.

To do this we use the following perl script
http://notes.asd.me.uk/wp-content/uploads/2012/08/vcal2text.txt

click on the link then

you can copy and paste the text into your own local file

name the file vcal2text

and save it in /usr/local/bin

Give the script execute permissions

chmod +x /usr/local/bin/vcal2text

Start up Mutt and all Vcard meeting requests will be Legible

Printing with Mutt

By default, when you press the p key to print a message in mutt, you will not be prompted to choose a printer. Mutt will just print to the printer defined in your PRINTER environment variable.

To change the printer mutt uses , from within mutt, type in the following:

:set print_command="/usr/bin/lp.cups"
Make sure you type in the colon first. If you do not type in the colon first, the rest of what you type will be interpreted by mutt as  commands (for example, the 's' from the word 'set' will try to save the message).

To see what your current printer command is, type in:

:set print_command
If you are using Gnome 3 and you would like to use your Default cups printer from within mutt, you can set your printer command as follows:

:set print_command="/usr/bin/lp.cups"
To make this setting permanent

edit your .muttrc file and put

set print_command="/usr/bin/lp.cups"

at the end of the file  like so

vim .muttrc
and this time without the :

set print_command="/usr/bin/lp.cups"

Install Gnome 3.4 weather extention on Fedora 17

su - yum install gnome-common gtk3-devel glib2-devel intltool automake autoconf vala wget gnome-tweak-tool


wget https://github.com/simon04/gnome-shell-extension-weather/zipball/gnome3.4
unzip gnome3.4
mv simon04-gnome-shell-extension-weather-* weather
cd weather
./autogen.sh --prefix=/usr
make 
make install
Restart Gnome [Alt] + [F2] r
Click on top right hand corner of desktop, Then click on advanced settings (gnome-tweak-tool)
Click on
Shell Extensions and turn on the weather indicator extension.
Next you need to set your area, open up your web browser and goto this site http://edg3.co.uk/
Enter your closest City to get your woeid eg my city is Valletta and the code is mtxx0001
In a non root terminal type the following to set your city
gsettings set org.gnome.shell.extensions.weather woeid mtxx0001
Substituting mtxx0001 for your own cities woeid.
You can also change the name of your City by typing the following would change the city name to "Mosta" which is my actual village gsettings set org.gnome.shell.extensions.weather city Mosta
To set the units to Fahrenheit or celcius, type one of the following.
gsettings set org.gnome.shell.extensions.weather unit celsius
gsettings set org.gnome.shell.extensions.weather unit fahrenheit
The position of the GNOME Shell extension in the panel can be configured to either 'left', 'center' or 'right' (requires restart of GNOME Shell). type one of the following
gsettings set org.gnome.shell.extensions.weather position-in-panel center
gsettings set org.gnome.shell.extensions.weather position-in-panel left
gsettings set org.gnome.shell.extensions.weather position-in-panel right

rc.local on suse

Suse does not have rc.local enabled by default.

which means it is difficult to have a program automatically start up, after your system has been booted.

Suse does have a file called /etc/init.d/boot.local.

However it is not the same as rc.local
Inputting paths to files to run in the boot.local file
executes them before going to the first run level.
Which is a problem if you need your application to run after the system has completely booted.

rc.local to the rescue.

simply create your own rclocal file like so.
I use vim but you can use any file editor program like nano or gedit
vim /etc/rc.d/rclocal

then inside the file type the following (between the -----)
--------------------------------------------------------------------------
#! /bin/sh
## This script simulates redhat's rc.local (Add commands at the end)
### BEGIN INIT INFO
# Provides: rclocal
# Required-Start: $local_fs $remote_fs $network
# X-UnitedLinux-Should-Start: $ALL
# Required-Stop:
# X-UnitedLinux-Should-Stop:
# Default-Start: 3 5
# Default-Stop: 0 1 2 6
# Short-Description: Simulates rc.local
# Description: Simulates redhat's rc.local: contains
# commands to execute after system has booted (all services are already
# available)
### END INIT INFO
## Execute ony when service is started
case "$1" in
start)
## commands will be executed
;;
*)
exit 0
;;
esac


#  Add your commands bellow this line

--------------------------------------------------------------------
Save the file.
Make the file executable by typing the following: chmod +x rclocal
Create symlink to make it easy to find:  ln -s rclocal rc.local
Next, you need to enable the rc.local simulation in yast.
Type
yast2
then scroll to
System > system services (Run Level)
then scroll down to
> rclocal   simulates rc.local
and enable it
 > Enable

Save your settings, and you are done.
you now have a rc.local that behaves exactly like the redhat/fedora  rc.local
You can add/remove commands to /etc/rc.d/rc.local anytime
by simply editing the rclocal file and adding your commands you wish to execute at the bottom of the file.

How to Upgrade from Fedora 16 to Fedora 17 (Beefy Miracle)

Insure that your system has more than 600MB of RAM, The upgrade requires this.(1GB or more is recommended)

First change to root user

su -

Upgrading To Fedora 17 (Desktop)
First upgrade your rpm package:

yum update rpm

Install the latest updates:

yum -y update

Clean the yum cache:

yum clean all

If a new kernel got installed during yum -y update, you should reboot the system

reboot

After the reboot, su back to root

su -


Install preupgrade...  (preupgrade will also take care of your RPMFusion packages)

yum install preupgrade

run preupgrade

preupgrade

The preupgrade wizard will then start on your desktop. Select Fedora 17 (Beefy Miracle). Your system will then prepare for the upgrade.

At the end, of the prepartion click on the Reboot Now button.
During the next boot make sure to catch the boot loader and select
Upgrade to Fedora 17 (Beefy Miracle).

During the reboot, your system will upgrade. This can take a  very long time, so please be patient.

(My system took about 4 hours)

That's it, Once Complete you can log into your new Fedora 17 (Beefy Miracle). system

To do the same on a Server that does not have X server (GUI) installed

Follow the same steps as above but run preupgrade with the following option

preupgrade-cli

preupgrade will show you a list of releases that you can upgrade to. included in that list will be

Fedora 17 (Beefy Miracle) 

[root@server1 ~]# preupgrade-cli

Loaded plugins: blacklist, langpacks, whiteout

No plugin match for: rpm-warm-cache

No plugin match for: remove-with-leaves

No plugin match for: auto-update-debuginfo

Loaded plugins: langpacks, presto, refresh-packagekit

please give a release to try to pre-upgrade to

valid entries include:

   "Fedora 17 (Beefy Miracle)"

[root@server1 ~]#

To upgrade, append the release string to the preupgrade-cli command:

preupgrade-cli "Fedora 17 (Beefy Miracle)"

Preupgrade will also take care of your RPMFusion packages, so all you have to do after preupgrade has finished is to reboot:

reboot

catch the boot loader and select Upgrade to Fedora 17 (Beefy Miracle).

that's it, your Done.

Power off machine after process is complete

This will check your machine for a specified process.

As soon as that process stops running , your machine will power off.

This is useful for example if you are using wget to download a large website.

you can then tell your machine to power off as soon as the website is finished being downloaded ie when wget is finished.

 while pgrep wget || sudo shutdown -P now; do sleep 1m; done

substitute wget for the process that you want to monitor.

Joining Linux server/workstation to Windows Active Directory

This  joins your Linux machine to a Windows Active Directory domain
and allows you to share your samba shares to users of the Active Directory domain without further authentication.

You need to install the latest version of Samba which is currently version 3
also  install samba-common, samba-client  and samba-winbind

yum install samba samba-client samba-common samba-winbind

if not already installed you also need to have
ntpd, and kerebos installed

yum install ntpd  kerberos

it is imperative that your linux machines clock is in sync with the active directory domain controller

ntpdate -u  [ip of your ADserver]

eg
ntpdate -u 192.168.1.10

next make sure that ntpd winbind and samba all start on boot up and are all running

chkconfig ntpd on
chkconfig winbind on
chkconfig smb on
/etc/init.d/ntpd start
/etc/init.d/smb start
/etc/init.d/winbind start

next edit your samba config file

vim /etc/samba/smb.conf

and change the following settings so that they are as they appear here.
Substitute CLIVE.COM with your Active directory domain name.
Also insure that you do not have a netbios entry.
If you have a line in your samba config file that says
netbios name = somename

delete the above line (if it exists)

the netbios entry will be added automatically by the system when you join the domain later.

your smb.conf should look something like this

 workgroup = CLIVE
        realm = CLIVE.COM
        preferred master = no
        server string = Samba File Server

 security = ADS
        encrypt passwords = yes
        log level = 3
        log file = /var/log/samba/%m
        max log size = 50
        winbind enum users = Yes
        winbind enum groups = Yes
        winbind use default domain = Yes
        winbind nested groups = Yes
        winbind separator = +
        idmap uid = 600-20000
        idmap gid = 600-20000
        hosts allow = 192.168.1.0/24 (put the ip of your network here)
        hosts deny = 0.0.0.0/0

Restart samba to load in the new config.

/etc/init.d/smb restart 

next you need to edit your kerberos config file

vim /etc/krb5.conf
and make the following additions
change CLIVE.COM for your AD domain name
and change servername to your active Directory domain controllers machine name.

case sensitivity is of extreme importance here.
[realms]
 CLIVE.COM = {
  kdc = servername.clive.com:88
  admin_server = servername.clive.com:749
  default_domain = clive.com
 }

 [domain_realm]
 .kerberos.server = CLIVE.COM
 .clive.com = CLIVE.COM
 clive.com = CLIVE.COM

save the file

and then run the following file to make sure everything is working as it should.

 /usr/kerberos/bin/kinit administrator@CLIVE.COM

You should be asked for the domain administrators password, once put in correctly you will return to a command prompt.

(Please note if you get an error here it is more than likely because your clock on your linux machine is not synced to your active directory domain controller)  check your clock and use ntpd to sync it properly.

next edit your nsswitch.conf file and change it so that it looks like this

vim /etc/nsswitch.conf

passwd:     compat winbind

shadow:     compat

group:      compat winbind

save the file and restart winbind

/etc/init.d/winbind restart

Edit your /etc/hosts file

vim /etc/hosts 

and insure you have the following line
127.0.0.1   hostname.clive.com hostname

remove localhost localdomain from the 127.0.0.1 entry

save /etc/hosts

 And now lets join your machine to the domain.

type

net ads join -U Administrator@CLIVE.COM

put in the administrators password and if all goes well your machine will be added to the domain

next type

wbinfo -u

to show a list of all the users of the Active directory domain.

in Samba to give access to an active directory user to your samba share,

edit the valid users line in your smb.conf file and add your active directory users like so,

substitute CLIVE for your domain name

[share]

        comment = share

        path = "/home/samba/shares/share/"

        browseable = yes

        writable = yes

        read only = no

        create mode = 0777

        directory mode = 2777

        valid users = CLIVE+administrator CLIVE+cliveg CLIVE+user2

to add an entire group ie Domain Users use the @

eg

valid users = "@CLIVE+Domain_users" 

don't forget to restart Samba every time you make changes to smb.conf.

Find 20 Largest Files on your system

Running out of Disk Space ?
want to see which files are the largest files on your system and are contributing to filling up your hard disk.
Copy and paste the following command into your terminal. and run it in your root directory.


find . -type f -print0 | xargs -0 du -h | sort -hr | head -20


This will  list the 20 Largest files on your System, and report their size in human readable format.

better still, copy and paste the line into a file,
name the file bigfiles
save the file in /usr/local/bin
chmod +x /usr/local/bin/bigfiles
then from anywhere on your system simply type 
bigfiles

Pimp your Tail command

The default settings of the TAIL command is to output the last 10 lines of a file

eg 

tail /var/log messages

will output the last 10 lines of your /var/log/messages file

Mar 24 11:25:20 mirage dbus-daemon[1094]: dbus[1094]

Mar 24 11:25:20 mirage dbus[1094]: [system] Successfully activated service 'org.freedesktop

Mar 24 11:27:44 mirage dbus-daemon[1094]: dbus[1094]: [system] Activating service name

Mar 24 11:27:44 mirage dbus[1094]: [system] Activating service name='net.reactivated

Mar 24 11:27:44 mirage dbus-daemon[1094]: Launching FprintObject

Mar 24 11:27:44 mirage dbus[1094]: [system] Successfully activated service 'net.reactivated.Fprint'

Mar 24 11:27:44 mirage dbus-daemon[1094]: dbus[1094]: [system] 

Mar 24 11:27:44 mirage dbus-daemon[1094]:

Mar 24 11:27:44 mirage dbus-daemon[1094]: ** Message: entering main loop

This alias changes the default setting of tail so that it outputs all the lines that can fit on your screen.

just add the following to your .bashrc if you use bash or your .zshrc if you use zsh as your terminal editor.

alias tail='tail -n $((${LINES:-`tput lines 2>/dev/null||echo -n 80`} - 7))'

then source youre .bashrc or .zshrc by typing

source .bashrc or

source .zshrc

or just restart your terminal

next time you run  tail on a file you will get as many lines as will fill up your screen.

play and edit MT2S files

MT2S files are High Definition Sony Blue ray AVCHD Files,
commonly produced by High Definition Camcorders.

To use edit and play these files on your Linux system
Openshot video editor works well as a video editor

yum install openshot or apt-get install openshot

although VLC can play these files you need to make the following changes to VLC so that they play well.

open up VLC


Go to Tools -->Preferences --> Input &  Codecs 
on the option “Skip the loop filter for H.264 decoding” select ALL 
Then in preference window Click Show Settings -> All. and expand Stream Output ->
Click Muxers ->select Mux module as “FFmpeg muxer”

next click

Expand Video -> Select Output module -> In Video Output module and select X11 video output.



and then save your settings

MT2S high definition files should play much more smoothly in VLC now.

Disable top left corner mouse Hotspot in Gnome 3

In Gnome 3, moving your mouse into the top left corner of your screen, simulates pressing (Alt-f1) or the Windows key, and puts you into search mode.  This can be extremely annoying when it happens accidentally.
 I prefer to only use the Keyboard for this feature.

to Disable the Mouse hotspot edit the following file

vim /usr/share/gnome-shell/js/ui/panel.js 


then search for the following line
this._hotCorner.actor.allocate(hotBox, flags);


and comment it out, by putting // infront of it
like so

// this._hotCorner.actor.allocate(hotBox, flags);


save the file, and logout/login to your Gnome session.

no more annoying mouse hotspot.

my .zshrc file

# Lines configured by zsh-newuser-install
HISTFILE=~/.histfile
HISTSIZE=100000
SAVEHIST=10000
setopt autocd
bindkey -v
# End of lines configured by zsh-newuser-install
# The following lines were added by compinstall
zstyle :compinstall filename '/home/cgerada/.zshrc'

autoload -Uz compinit
compinit
# End of lines added by compinstall

#the following lines were added by cgerada
#autocompletion of hostname from ,ssh/known_hosts

local _myhosts
_myhosts=( ${${${${(f)"$(<$HOME/.ssh/known_hosts)"}:#[0-9]*}%%\ *}%%,*} )
zstyle ':completion:*' hosts $_myhosts
#Spelling autocorrect
setopt  correct

#coloured prompt
autoload -U colors && colors
PS1="%{$fg_bold[green]%}%n%{$reset_color%}@%{$fg_bold[blue]%}%m %{$fg_bold[yellow]%}%~ %{$reset_color%}%% "
# right hand prompt simple date and time only
 RPROMPT="[%D,%T]"

#Extension aliases very cool
alias -s doc=libreoffice
alias -s xls=libreoffice
alias -s doc=libreoffice
alias -s pdf=evince

~                                                                                                                                                          
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Moving from Bash to ZSH

I have Stopped using Bash and am now using ZSH as my new shell of Choice.
ZSH has many awesome features that make it a No brainer (for me anyway) to make the switch

Here's what I love about ZSH

1:) Your History is shared across sessions. Multiple simultaneously running zsh sessions can share history with each other. how many times have you looked into your bash history to find a recent command that you used, only to find that that command was run on a different terminal session and is no longer available to you.

2:) Tab Auto completion works between remote machines over SSH.

rsync -avr remotemachine:/home/cgerada/Documents/very/long/directory/na (at this point you can hit tab and provided that you connect to your remote host using ssh Key authentication instead of password authentication  zsh will autocomplete for you.

3:)No need to type cd to change into a Directory.
/home/cgerada/directory   enter

will change to /home/cgerada/directory  for you.
Considering how often you use the cd command, this is a real time saver.

4:) Tab auto completion works for command options
     rsync -av (hit tab here) will show you all possible options for the rsync command

5:) Built in Spell check
     How many times have you typed something like aptg-et or other mangled commands? Well,
     if you do that in zsh,You  get a message asking: “zsh: correct 'aptg-et' to 'apt-get' [nyae]? “

6:) Built in pager.
     If your Lazy like me. And I think you are.  zsh comes with a pager directly in the shell. This means you
     can type things like " > README  and it is equivalent to less README or cat README | less"


7:)Right hand prompt
    Zsh supports a second (right hand prompt) great for adding the date and time (see screen shot above)
    or if you own a laptop you can also display your Battery capacity.  The right hand prompt will not get in
    your way as it disappears when your typing reaches it. or you can just not enable it if you don't want it.

8:) Known hosts auto completion. ZSH can even tab autocomplete hostname entries of remote machines that  
     you connect to from your .ssh/knownhosts file.

     in fact auto completion in all areas is far more superior in ZSH.

9:) Extension aliases

alias -s doc=libreoffice





putting the above in your .zshrc file allows you to open up a .doc file simply by typing its filename. eg

officedoc.doc  [enter]

will open up officedoc.doc using libre office (in Bash you would have had to type

libreoffice officedoc.doc
you can do the same for all extensions eg
alias -s pdf=evince
                      
ZSH has loads more awesome features, and is highly customizable .  it behaves extremly similar to bash, in fact you can use it exactly the way you use bash and not learn or change a single thing and you won't be missing anything.

Right, so if you are convinced to make the change and jump right in.

install zsh by typing  yum install zsh or apt-get install zsh.

once installed simply type
chsh to change your shell  .
you will be asked for your user password
once typed in correctly you will be asked
New shell [/bin/bash]
type /bin/zsh   enter

and the next time you log into your shell with your username you will be in the ZSH shell.

If for what ever reason, you do not like zsh and want to revert back to bash
simply type
chsh
enter your password once again
and then type
/bin/bash

will change your shell back to Bash.

X11 connection rejected because of wrong authentication.

When you need to run an X window application over SSH.
You ssh -X into the remote machine, running X applications works fine, until you
sudo or su to another user to run an X application , You get the following error.
"X11 connection rejected because of wrong authentication.

X connection to localhost:10.0 broken (explicit kill or server shutdown)."

or if you connected using putty the error will read.
“Xlib: PuTTY X11 proxy: wrong authentication protocol attempted”.


How to fix?


ssh cgerada@remote-server -X


cgerada $ su – oracle
oracle‘s Password:
oracle $ xclock


"X11 connection rejected because of wrong authentication.
X connection to localhost:10.0 broken (explicit kill or server shutdown)".

or if you connected with putty the error reads


"Xlib: PuTTY X11 proxy: wrong authentication protocol attempted
xclock Xt error: Can’t open display: localhost:10.0"


On newer versions of  OpenSSH Server releases, you can simply enable “ForwardX11Trusted yes” in the /etc/ssh/sshd_config file and restart the OpenSSH server.
If you’re using an older version of  OpenSSH Server release then
You need to temporarily transfer the authorization to the other account. First, get the key from your account:
cgerada $ xauth list
fileserver/unix:10  MIT-MAGIC-COOKIE-96951c0622f80fd52186129dd06f2f6
Next, sudo/su to the other account and add the authorization key.
cgerada $ su – oracle
oracle $ xauth add fileserver/unix:10  MIT-MAGIC-COOKIE-96951c0622f80fd52186129dd06f2f6
Now, you should be able to start any X Windows application, 
oracle $ xclock