Everyone is going to tell you to use dd. dd if=/dev/oldsdcard of=/dev/newsdcard
Personally, I have actually eaten an entire system by getting the wrong /dev names for the input file and the output file.
Gparted lets you copy whole partitions and resize them, and is graphical. I have yet to destroy my computer using gparted, but I’ve definitely done so with dd. (I’m also an idiot though, so…) Edit: gparted will also let you resize the new SD to the bigger partition size! However, it is actually possible to break your system in gparted too, so make sure you aren’t deleting partitions and stuff in there.
No! You shouldn’t have told me that it could be done! Now, the next time I launch gparted, I’ll somehow manage to wipe everything! Not just my system, but, like, all my systems! If it can be broken on a computer, I’ll be the one to break it!