Create-Special-User-on-Ubuntu

Create a User WithOut Login through GUI
=================================

User "-r" Option with useradd command

# useradd -s /bin/bash -G sudo -m -r svk
# passwd svk
# su - svk

# mkdir /usr/svk
# chown -R svk: /usr/svk

Create some special Command for that user to Run
---------------------------------------------------------------------------------------

$ cat .profile
...
# set PATH so it includes user's private bin directories
PATH="/usr/svk:$HOME/bin:$HOME/.local/bin:$PATH"
$

$ cat /usr/svk/psql-aws
#!/bin/bash
if [ -z $1 ]; then
    psql -U svk -h odoo-pgsql-xxxxxxxxxx.rds.amazonaws.com
else
    psql -U svk -h odoo-pgsql-xxxxxxxxxx.rds.amazonaws.com -c $1
fi
$
$ chmod +x /usr/svk/psql-aws

APT-update failed error on UBuntu 10.04

Edit the /etc/apt/sources.list file with a text editor,
and wherever see the archive.ubuntu.com (the source of releases actively supported), change it to old-releases.ubuntu.com

# vi /etc/apt/sources.list
....
:%s/archive.ubuntu/old-releases.ubuntu/g
#

Ubuntu-16-Tweaks

“Create new document” - right-click option ====================================
Create one if not, ~/Templates folder.

$ touch ~/Templates/Text\ File.txt
$ touch ~/Templates/Text\ File.txt

"Create Document" option is back again and you can create a new text file or a new document.

Set-Sh-File-to-Ask-on-Opening
====================================

$ gsettings set org.gnome.nautilus.preferences executable-text-activation ask

Rename-Network-Device
====================================

Edit your /etc/default/grub changing the line from
GRUB_CMDLINE_LINUX="" to
GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0"

# vi  /etc/default/grub
...
GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0"
...
#
# update-grub
# sudo reboot

Change the Default Text Editor on Ubuntu
==========================================

$ sudo update-alternatives --config editor
There are 3 choices for the alternative editor (providing /usr/bin/editor).
  Selection    Path               Priority   Status
------------------------------------------------------------
  0            /bin/nano           40        auto mode
  1            /bin/ed            -100       manual mode
* 2            /bin/nano           40        manual mode
  3            /usr/bin/vim.tiny   10        manual mode

Press to keep the current choice[*], or type selection number:
$

To change the default editor to vim,  just hit the number 3.

Change the Default TimeZone
==========================================

# dpkg-reconfigure tzdata
# cat /etc/timezone 

LightDM-Tweaks

To Disable Guest-User from LightDm-LoginScreen
=======================================
# vi /etc/lightdm/lightdm.conf.d/50-myconfig.conf
[SeatDefaults]
allow-guest=false
#

To Enable Manual Login Screen on LightDm-LoginScreen
=======================================
# vi /etc/lightdm/lightdm.conf.d/50-myconfig.conf
[SeatDefaults]
allow-guest=false
greeter-hide-users=true
greeter-show-manual-login=true
#

To Enable AutoLogin on LightDm-LoginScreen
=======================================
# vi /etc/lightdm/lightdm.conf.d/50-myconfig.conf
[SeatDefaults]
allow-guest=false
greeter-hide-users=true
greeter-show-manual-login=true
autologin-user=ubadmin
#


========================================

Simple-Samba-Server-LinuX

Install and Configure Samba

# yum install samba
OR
# apt-get install samba

# useradd -c "Samba_User1" -d /dev/null -s /bin/false smbu1
# useradd -c "Samba_User1" -d /dev/null -s /bin/false smbu2

# smbpasswd -a smbu1
# smbpasswd -a smbu2

# groupadd SambA

# usermod -aG SambA smbu1
# usermod -aG SambA smbu2

# mkdir -p /samba/share
# chown :SambA /samba/share
# chmod 775 /samba/share

(Here Files created by smbu1 cann't delete files of smbu2 on "/samba/share" Directory and vice versa)

# vi /etc/samba/smb.conf
[global]
workgroup = WORKGROUP
security = user
[ShaRe]
path = /samba/share
valid users = smbu1, smbu2
read only = no
guest ok = no
;instructs samba to allow this share to be displayed on the client network browser.
browsable = yes
#

For-Ubuntu

# systemctl restart smbd
# systemctl enable smbd

For-CentOS

# systemctl restart smb
# systemctl enable smb

# testparm

-----------------------------
Remember that your user must have permission to write and edit the folder you want to share.
For Ubuntu--->Also hide the user on the login screen and allow manual Login adjusting lightdm's configuration

# vi /etc/lightdm/lightdm.conf.d/50-myconfig.conf
[SeatDefaults]
allow-guest=false
greeter-hide-users=true
greeter-show-manual-login=true
#
-----------------------------

Allow Samba Through FireWall Rules
================================

# firewall-cmd --list-all
# firewall-cmd --get-services ---> To get the names of pre-defined services ( Name "samba" will be there)

# firewall-cmd --add-service=samba --permanent
# systemctl restart firewalld

# cat /usr/lib/firewalld/services/samba.xml  ---> For Samba Ports Description


To access your network share
================================

# yum install samba-client
OR
# apt-get install smbclient

List all shares:

# smbclient -L /// -U

connect:

# smbclient /// -U

To access your network share use your username () and password through the path

Linux users     ------ "smb:////"
Windows users     ------ "\\\\"

Note that "" value is passed in "[]", in other words, the share name you entered in "/etc/samba/smb.conf".

    Note: The default user group of samba is "WORKGROUP".
OR
# apt install cifs-utils
# mount -t cifs //10.10.10.101/iso/LinuX/Ubuntu /smb-mnt/ -o username=test,noexec

# mount -t cifs //10.10.10.101/Videos -o username=user1 /mnt/samba/videos
# mount -t cifs //10.10.10.101/Videos -o username=user1,password=mypassword /mnt/samba/videos
================================

AdM-TiPs

1.Split larger files Using 7-zip

----------------------------------------------

# 7z   a   -v50m   -mx0    ubuntu.7z     /test/ubuntu.iso

This will create 50MB size files from the ubuntu.iso. The -v50m is the volume size(use k for kilobytes& g for gigabytes) etc; the -mx0 switch tells 7-Zip to use no compression, that is, just to split data into parts.

To extract just do
#  7z   x   ubuntu.7z.001  
OR
# 7z  e  ubuntu.7z.001

2.Binary-Decimal Conversion
--------------------------------------------------
To Get the decimal value of Binary num 10000000
$echo "ibase=2; 10000000"|bc
To Get the Binary value of Decimal Num 254
$echo "obase=2; 254"|bc

3.To Redetect  Network Card

---------------------------------------------
Comment the acive network line in the files and reboot to redetect network card

/etc/udev/rules.d/70-persistent-net.rules

4.To configure wake-on-lan:
-----------------------------------------------
Install wakeonlan or ether-wake package
Install ethtool in remote system

#apt-get install ethtool
edit /etc/rc.local to add this line before the exit 0 line:

ethtool -s eth0 wol g

or execute  # ethtool -s eth0 wol g
Find out the MAC address of Remote Machine's network card (replace ethX with eth0/eth1, ..):

#ifconfig ethX | grep "HWaddr" | awk '{print $5}'

shutdown the Remote machine. Invoke the below mentioned command from ur System:

#wakeonlan RemoteSys_mac_id

5.Hide Other HDD drives from Nautilus Window
--------------------------------------------------------------------------------
Create a file in /etc/udev/rules.d/  as follows to hide the drives “sda1,2 &7”   as root user
# vi   99-hide-disks.rules 
KERNEL=="sda1",ENV{UDISKS_PRESENTATION_HIDE}="1"
KERNEL=="sda2",ENV{UDISKS_PRESENTATION_HIDE}="1"
KERNEL=="sda7",ENV{UDISKS_PRESENTATION_HIDE}="1

6.Disable Password prompt for sudo commands
----------------------------------------------------------------------------
Edit the %sudo line in /etc/sudoers file as follows
#  vi   /etc/sudoers
%sudo     ALL=(ALL:ALL)   NOPASSWD:   ALL

7.VBOX Driver/VBoxGuestAddition  innstallaton on Linux
-----------------------------------------------------------------------------------------------------
#yum install kernel-devel kernel-headers kernel-PAE-devel gcc SDL Qt gcc-c++
#yum install dkms --------> Optional Required for Host
#export KERN_DIR=/usr/src/kernels/2.6.33.3-85.fc13.i686.PAE/ ----> Optional
For Ubuntu
$ sudo apt-get install build-essential

mount VBOXGuest addition package... and run ./VBoxLinuxAddition.run

8.To add NTFS file system support 
-----------------------------------------------------------------
Install "fuse" and "fuse-ntfs-3g" packages 

9.To display storage controllers and N/W Card in the system

---------------------------------------------------------------------------------------------------
#lshw -class disk -class storage
#lshw -class network

10.Force umount when the device is busy
----------------------------------------------------------------
# fuser -km /mnt/hda2

11.To find the installed package of a Command.
-------------------------------------------------------------
# which  ls   -----  To find the location of command
# rpm    -qf    /bin/ls  
For Ubuntu
# dpkg   -S   /bin/ls

12.How to umount when the device/mounted directory is busy
----------------------------------------------------------------------------------------
# umount /storage 
umount: /storage: device is busy
umount: /storage: device is busy

This error comes when some running services use this device/directory.So Find out the process ID of the services ,which using the device and kill them one by one ,use the fuser command
# fuser -m /storage or # fuser –m /dev/hdd3
/storage: 2110 2115 2116 2230 ---->Output of the above command..The find the running process using PID
# ps auxw grep 2110 (For Checking the name of process)
Finally Kill each process or stop associated services.
# kill -9 2110 2115 2116 2230
Now the device/directory will be able to umount

Reinstall-Grub-on-LivaPC

1.Boot From Live-CD

2.Mount the Installed Disk to /mnt from root user

( Root Disk will be sda1 or mmcblk0p2 ,check the same using fdisk/gparted utility and change accordingly )

# mount /dev/mmcblk0p2 /mnt
# mount /dev/mmcblk0p1 /mnt/boot/efi
# mount --bind /proc /mnt/proc
# mount --bind /sys /mnt/sys
# mount --bind /dev /mnt/dev

3.Chroot to /mnt

# chroot /mnt
    (    Check internet connection "# ping google.com" ,if not check "# ping 8.8.8.8" ,if working run
        # echo "nameserver 8.8.8.8" >> /etc/resolv.conf    
     )

# apt-get update
# apt-get install grub-efi-amd64  
(Remove grub-common,grub2-common if errror , and then install grub-efi-amd64)

# grub-install /dev/mmcblk0
# update-grub2     (OR # update-grub)
# exit

4.Umount and Reboot

# umount /mnt/dev
# umount /mnt/sys
# umount /mnt/proc
# umount /mnt/boot/efi
# umount /mnt
# reboot

Install-Win8.1-in-Pendrive-UEFI

Do the following steps from a Windows System
   
On-ComandPrompt    
   

    C:\> diskpart

In the elevated command prompt, type the commands below one at a time and press Enter after each one.

    DISKPART> list disk

Make note of the Disk # (ex: Disk 4) for the USB flash drive. (see screenshot below step 5) NOTE: Substitute # in the first command with the actual disk # from step 4 above. For example: select disk 4

    DISKPART> select disk #
    DISKPART> detail disk (this is to verify that you selected the correct disk before using "clean" )
    DISKPART> clean
    DISKPART> create partition primary
    DISKPART> format fs=fat32 quick
    DISKPART> active
    DISKPART> assign
    DISKPART> list volume
    DISKPART> exit

Make note of the volume letter (ex: K) for the USB flash drive in the command prompt.

If Using a Windows 7 or Windows 8/8.1 Installation DVD

A) Insert the Windows 7 or Windows 8 installation DVD into the CD/DVD drive.
B) In the Computer window, open the DVD. (see screenshot below)
C) Select all files in it, right click or press and hold on the selected files, click/tap on Send to and the Removable Disk for your USB flash drive letter (ex: K) from step 6 above. (see screenshot below)
D) This could take a bit to copy the DVD contents to the USB.

Now Boot the USB in UEFI mode

Windows-7-Can't-Complete-Installtion

Resolve-Windows-7-Can't-Complete-Installtion-Error
-----------------------------------------------------------------------

During the windows 7 installation  after the first restart , may get an like "Windows could not complete the installation.To install Windows on this computer,restart the installation".

Because of this error new user creation window will not appear ,so need to do this manually in-oder to complete the installation  Do the following steps to resolve this issue

When prompted with error unable to complete installation:
Hit SHIFT-F10 to bring up command prompt.

type MMC
Click File -> Add/Remove Snap-in... (Or CTRL+M)
Select Computer Management (Double click and Finish on Local Computer)
Click OK
Double click Computer Management (Local) -> System Tools -> Local Users and Groups -> Users -> Double Click Administrator -> Uncheck Account is disabled -> OK
Now right click Administrator -> Set Password...  ->  Set a decent password to get started.

Now, restart. 

If this doesn't work try next step:

SHIFT-F10 to bring up command prompt.
type:  CD C:\windows\system32\oobe
type msoobe
enter
Make a generic account and password.  hit finish
Set time/date.  Finish.
Restart.
 
Should be good to go.