I've got question about following situation: if i have closed source binary and device with Linux, i want to sell this device with Linux and closed binary in its filesystem. Is it legal to keep source of this binary closed, or it become GPL? Thank you
The Linux kernel and the GNU C and C++ libraries have exceptions in their GPL license to allow closed source applications to use them.
Thus, if your closed source binary only depends on Linux itself and libraries with a permissive license or a permission to link against closed source code, it is legal to distribute the closed source binary without disclosing its source code. This is independent of if you distribute just the binary or if you distribute it installed on a device.
If you distribute a device with Linux (and other GPL code) on it, you are still required to inform the recipient of the device of their rights under the GPL license and where/how they can obtain the GPL-licensed code. You are just not required to include the source code of your closed-source binary in that.