I have a Western Digital MyBook external hard drive. It generally works fine, but often when I try to copy a file to the drive, I get "The operation can't be completed because an unexpected error occurred (error code -50). If I try using the cp command in the terminal instead, I get "Invalid argument". If I then try to eject the drive and remount, everything works fine.

It seems that these hard drives spin down after about 10 minutes of inactivity. That doesn't really bother me, and I'm not positive this is the issue, as I can browse around the drive fine once it spins up again, but I still get the copy error.

Any suggestions?


Disk format is Mac OS Extended (Journaled)

Example of cp command I used: cp /Users/Ben/Desktop/test.txt /Volumes/Media

  • which data system are you using ? FAT 32 or NTSFS? – Fabian Gr Jul 23 '18 at 5:15
  • What's the cp command you're using? It tough to diagnose an invalid argument when we can't see the actual arguments. – Allan Jul 23 '18 at 12:55
  • @FabianGr thanks for your input, I've updated the question to answer your query – Ben Williams Jul 23 '18 at 23:08
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    In terms of the file system a -50 error refers to a paramErr: Error in user parameter list. There are a number of scenarios that can trigger this error (e.g. if filenames use certain characters not compatible with the file system of the disk you're copying to). Since your external drive is formatted with Mac OS Extended (Journaled), this isn't going to be the cause of your problem. – Monomeeth Jul 30 '18 at 11:29
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    @Monomeeth I haven’t had the problem once since updating to 10.13.6, so I’m reasonably hopeful it’s fixed now. Either way you’ve given a lot of useful suggestions, so if you want to post an answer I’m happy to send the bounty your way. – Ben Williams Aug 5 '18 at 9:54

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