I am not as familiar with it as others may be, but "DD Rescue" is one method that is free and reliable.
There is also Image for Linux. I have it but don't use it because I don't generally make backups of my Linux installs. But I do often use, and have for years, 'Boot It' and 'Image for Windows' from the same company with great success.
Some other might chime in with some other options.
Ultimate Edition Linux
AMD FX 8350
Asus Sabertooth 990FX R2.0
24GB GSkill/Corsair 1866MHz
EVGA GTX 970 SSC/ GTX 650 (PhysX)
SSD - OCZ V4 128GB/Kingston 120GB
HDD - 3TB/2x 750GB/500GB
CM HAF 932 Red
CM Hyper 212 EVO w/2x 120mm Red
Logitech X540 5.1
2X Acer 23" LED - Surround: 3840x1080
Microsoft Sidewinder x4 KB
"The significant problems we face cannot be solved at the same level of thinking we were at when we created them."
- Albert Einstein