Installing GNS3 on CentOS/RHEL 6

1. Login as root and run the following (accept all dependencies):
   yum install python python-devel xorg-x11-proto-devel libXext-devel gcc-c++ libXrender* PyQt4 PyQt4-devel qt qt-devel qemu-img libvirt
   
2. Download the latest GNS3 source, unpack it to /opt, create symbolic link, create subfolders and set permissions (at this time, the GNS3 version is 0.8.3, but a newer version might be available – it’s your call as to which version to use):
   wget http://iweb.dl.sourceforge.net/project/gns-3/GNS3/0.8.3/GNS3-0.8.3-src.tar.gz
tar -xvf GNS3-0.8.3-src.tar.gz -C /opt
cd /opt
ln -s GNS3-0.8.3-src GNS3
cd GNS3
mkdir Dynamips IOS Project Cache Temp
chmod o+rw Project Temp 
3. Change directory into Dynamips, download the binary and make it executable (at this time, the Dynamips version is 0.2.8-RC3, but a newer version might be available – it’s your call as to which version to use and the URL to download it):
   cd Dynamips
wget http://downloads.sourceforge.net/project/gns-3/Dynamips/0.2.8-RC3-community/dynamips-0.2.8-RC3-community-x86_64.bin
chmod +x dynamips*.bin
4. Download GNS3 icon from here and link in the right locations:
   cd /opt/GNS3
wget http://www.rehmert.com/wp-content/uploads/2012/08/gns3-150x150.png
ln -s /opt/GNS3/gns3-150x150.png /usr/share/icons
ln -s /opt/GNS3/gns3-150x150.png /usr/share/pixmaps
5. Create a /usr/bin/gns3 with the following content:
   #!/bin/bash
python "/opt/GNS3/gns3"
   
6. Set +x on /usr/bin/gns3:
   chmod +x /usr/bin/gns3
7. Create app for use in app menu and launcher creation
   Create /usr/share/applications/gns3.desktop with the following contents:
   [Desktop Entry]
Name=GNS3
Comment=GNS3
Exec=gns3
Icon=gns3-150x150.png
Terminal=0
Type=Application
Encoding=UTF-8
Categories=Development

8. Now you’ll find GNS3 listed in the Applications -> Programming menu location and can create application launchers in panels or on the desktop with ease…
9. Edit /opt/GNS3/src/GNS3/Node/AbstractNode.py to comment out the following lines:
   if QtCore.QT_VERSION >= 0x040600:
flags = flags | self.ItemSendsGeometryChanges
   To avoid the following error message:
   AttributeError: 'xxxxxxxxxxx' object has no attribute 'ItemSendsGeometryChanges'
Source: http://www.rehmert.com/2012/08/installing-gns3-on-centosrhel-6/