Linux Tips, Ubuntu Centos RedHat

SSH check:

cat /etc/ssh/sshd_config |egrep -iv '^#' | egrep -i 'Protocol|UseDNS|PermitRootLogin|AllowUsers|DenyUsers|Port|LoginGraceTime|ListenAddress|ClientAliveInterval|ClientAliveCountMax'

Port 60022
ListenAddress x.x.x.x
Protocol 2
PermitRootLogin no
ClientAliveInterval 600
UseDNS no
should be:
- Protocol 2
- PermitRootLogin no
- AllowUsers ramesh john jason
- ClientAliveInterval 600 - ClientAliveCountMax 0

skype on centos x64
yum whatprovides */
yum install qtwekit-2.1.1-1.el6.i686

To remove all oprhaned packages automatically try:
package-cleanup --quiet --leaves --exclude-bin | xargs yum remove -y

Redhat / Centos , sudo - root access

1) Log in to the system as the root user.
2) Create a normal user account using the useradd command.
# useradd <USERNAME>
3) Set a password for the new user using the passwd command.
# passwd USERNAME
Changing password for user USERNAME.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.
4) Uncomment in file /etc/sudoers :
### Do not uncomment this line# Allows people in group wheel to run all commands
# %wheel        ALL=(ALL)       ALL
5) Add the user you created to the wheel group using the usermod command.
# usermod -aG wheel USERNAME
6) Check

$ groups

$ sudo whoami

Ubuntu Autocompletion

I'm using Xubuntu and connecting over RemoteDesktop with Windows 7.
Everything works fine, but the auto_completion in my bash doesn't work. Solution:
You may find that this is a more general issue with interception of the Tab key under remote XFCE4 sessions, rather than a problem with bash completion itself.
I had a similar issue running XFCE4 over VNC and the workaround for me was to edit the ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-keyboard-shortcuts.xml file to unset the following mapping
<       <property name="&lt;Super&gt;Tab" type="string" value="switch_window_key"/>
>       <property name="&lt;Super&gt;Tab" type="string" value="empty"/>
I found this solution online somewhere and can't really take credit for it.

GNS3 Configuration
1. How to send command to multiple consoles (Terminals).
Using Konsole (Ubuntu terminal application):
1) create 2 hotkeys:
  ALT+W - All tabs in current window
  CTRL+ALT+W - none
2) select any tab (router), type "ALT+W" wr ↵  "CTRL+ALT+W"    and 'wr'  will be executed in every tab
2. Clear Cisco router configs:
erase startup-config
configure replace nvram:startup-config force
3. Setup annoying features (send to all routers using step 1)
conf t
no ip domain-lookup
alias exec sib show ip int br
alias exec rib show ip route
alias exec run show run
alias exec ro show run | section router
line con 0
exec-timeout 0 0
privilege level 15
logging synchronous
4. TCL script to ping multiple destinations at once
Branch# tclsh
foreach address {
} { ping $address}
Another TCL script
puts [open "nvram:helper" w+] {
+>Welcome to Help Menu.
+> sh vrf br - list all VRF-s
+> Following Aliases available:
+>  bgp - sh bgp vpnv4 unicast vrf INTERNET summary

Configure Ubuntu 13.10 on ESXI 5.0 host

Reset root password -

1) Update system
Work as root, not hit every time 'sudo'

sudo -s
apt-get update
apt-get install build-essential
apt-get install linux-headers-$(uname -r)

2) Install VMWare Tools

# insert VMWARE-tools in virtual CD-ROMmkdir /media/cdrom
mount /dev/cdrom /media/cdrom
mkdir /usr/vmtools
cp /media/cdrom/VMwareTools*.tar.gz /usr/vmtools
cd /usr/vmtools
tar xvf VMwareTools*.tar.gz
cd /usr/vmtools/vmware-tools-distrib
./ -d

3) Install GNS3 0.8.6
add-apt-repository ppa:gns3/ppa
apt-get update
apt-get install dynamips gns3

4) Install TeamViewer 9
apt-get install gdebi
gdebi teamviewer_linux.deb
To completly uninstall Teamviewer 9 (if VM cloning)
stop teamviewer
apt-get purge teamviewer
rm -r /home/<user>/.config/teamviewer9
5) Set Desktop Custom resolution
xrandr --newmode "1920x1080"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
xrandr --addmode Virtual1 1920x1080
xrandr --output Virtual1 --mode 1920x1080
6) Set promisc mode (for VMWARE network transit to real network)
ifconfig eth0 promisc up
ifconfig eth1 promisc up  

Old info (for ubuntu 12.10 and teamviewer 8, GNS3 0.8.4)

! Enable SSH Server
apt-get install openssh-client
apt-get install openssh-server
cp /etc/ssh/sshd_config /etc/ssh/sshd_config.original
chmod a-w /etc/ssh/sshd_config.original
/etc/init.d/ssh restart
If kernel headers are not found, this will helps:
cd /lib/modules/$(uname -r)/build/include/linux
sudo ln -s ../generated/utsrelease.h
sudo ln -s ../generated/autoconf.h
sudo ln -s ../generated/uapi/linux/version.h 

! or run vmware-toolbox
! Install GNOME3
sudo apt-get install ubuntu-gnome-desktop ubuntu-gnome-default-settings
! make sure to select gdm as default display manager when prompted, if not correct with 'sudo dpkg-reconfigure gdm'
! install additional GNOME apps
sudo apt-get install gnome-documents gnome-boxes
sudo add-apt-repository ppa:gnome3-team/gnome3
apt-get update && apt-get upgrade

GNS3 Settings
IDLEPC = 0x????????

Many consider this “THE” most important part of GNS3 configuration.
It can dramatically change your overall experience.
Basically, this value defines the resources the emulated Cisco Routers will use. The IDLE PC value instructs devices to release resources and go idle during while the router is running idle. This then allows resources to be freed up and made available to the other devices. It is kind of co-operative multi-tasking being done among the emulated instances. You should spend sufficient time to find a good combination of IDLEPC value suited for his/her IOS and computer platform.

 R1#dir  disk0:
%Error opening disk0:/ (Invalid DOS media or no media in slot)

R1#show disk0:
Unformatted Partition, please format it.

R1#format disk0:
Format operation may take a while. Continue? [confirm]
Format operation will destroy all data in "disk0:".  Continue? [confirm]

Primary Partition created...Size 64 MB

Drive communication & 1st Sector Write OK...
Writing Monlib sectors....
Monlib write complete

Format: All system sectors written. OK...

Format: Total sectors in formatted partition: 131040
Format: Total bytes in formatted partition: 67092480
Format: Operation completed successfully.

Format of disk0: complete

R1#show disk0:
No files on device
66875392 bytes available (0 bytes used)

R1#copy tftp: disk0:

Boot from disk0 device
boot system flash disk0:c7200-adventerprisek9-mz.124-24.T5.bin

R1(config)# username test privilege 15 secret cisco
R1(config)# ip http server
R1(config)# ip http authentication local
*Apr 15 13:44:55.571: %LINEPROTO-5-UPDOWN: Line protocol on Interface EDSP0, changed state to up

Start CCP as Administrator

Windows 7 add loopback adapter

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