The system was originally UBUNTU14, the first two days after installing Win7, the start is directly win7. That is, the Ubuntu startup item disappears.
Try a very many methods under Windows, all failed, and finally choose Ubuntu under Boot-repair software to fix the boot entry.
First of all. Write the Ubuntu system to the USB flash drive.
Write process details: http://jingyan.baidu.com/article/d169e186800f02436711d87b.html.
The process is relatively simple, but also self-Baidu.
Then, the USB stick starts Ubuntu.
Select try after starting. When you go to the desktop, open the terminal, CTRL + ALT + T, or search for terminal in the search bar.
Add Boot-repair software Source: sudo add-apt-repository ppa:yannubuntu/boot-repair
Update software Source: sudo apt-get update
Installing Boot-repair:sudo apt-get install-y Boot-repair
Start: Boot-repair
For example, with:
You can fix it by clicking the arrow at the end.
Fix the problem of installing Windows7 causing Ubuntu startup item to disappear