$ download and extract $ cd /path/to/osx-pl2303.kext $ sudo cp -R osx-pl2303.kext /System/Library/Extensions/ $ next you need to fix permissions and execute bits: $ cd /System/Library/Extensions $ sudo chmod -R 755 osx-pl2303.kext $ sudo chown -R root:wheel osx-pl2303.kext $ cd /System/Library/Extensions $ sudo kextload ./osx-pl2303.kext $ sudo kextcache -system-cache
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