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Sometimes when I remove SD card I can notice that when I reinsert it - it doesn't mount by itself. Also I've notice that umount process is stalled and I cannot kill it (not even with -9). I use Ubuntu 14.04.

Any idea what I do wrong?

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First things first: get out from that directory :) Joking.. but not so much, thinking how many times I run umount and it gives me back an error because I'm indeed inside the mounted folder.

Try running lsof | grep <your_sd_card_directory_here>, to check if that directory is in use.

Example output of lsof | grep /mnt/share, /mnt/share is mounted:

COMMAND     PID  TID    USER   FD      TYPE             DEVICE  SIZE/OFF       NODE NAME
lsof      11930         root  cwd       DIR              253,2        15     213678 /mnt/share

This is showing that lsof is being run exactly from /mnt/share with FD (File Descriptor) cwd, the Current Working Directory.

If you see the same.. get out from that directory ;)

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  • Can this be related to copying a file onto that SD card and removing the card without sync'ing?
    – lewiatan
    Nov 13 '15 at 8:35
  • What you mean by sync'ing? Is the sd configured to be synced in some program? If the sd mount directory and related files/services are free, you should be able to unmount and mount it again. Try findmnt, it should tell you where exactly is the sd mounted, and then use lsof | grep sdmountpoint to find out what actually is using it.
    – nnsense
    Nov 13 '15 at 14:31
  • I meant that I used "cp" instruction earlier and later "sync" in the terminal. Unfortunately I resolved the issue with hard reset but I'm sure it will come back and then I'll post the output of findmnt, lsof and iostat.
    – lewiatan
    Nov 13 '15 at 17:52
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umount process is stuck in system call and kernel waiting for something - perhaps it's a bad driver issue, because normally USB drivers correctly handle such situations and let userspace processes go on to exit, instead of hanging them into kernel mode, when user suddenly pulls out USB stick or SD card from reader.

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