There are three common pronunciations of Linux. All three are quite acceptable.
The only proper pronunciation is the one used by Linus Torvalds himself. The name Linux is a derivative of his name, and thus is pronounced like his name. Linus pronounces his name "Lee-noos", so Linux is properly pronounced "Lee-nooks".
A linguistically acceptable pronunciation is based on the Anglicized pronunciation of Linus, which is "Lie-nus". Hence, an acceptable Anglicized pronunciation of Linux is "Lie-nuks".
However, there is a third common pronunciation of Linux, which is "Lin-icks" (or sometimes "Lin-ucks"). This pronunciation has no basis as a linguistic derivative. It does, however, sound more like "Unix", which is probably the reason it came about.
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guh-new lih-nucks