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I am using a USB with an embedded device running linux. The issue is that in some cases when I unmount the usb by giving the command umount /media/sda1 the unmount is successful but when I proceed to remove the usb I get an error saying unable to mark fs as dirty and when I plug it back in I get the error Volume was not properly unmounted. Some data may be corrupt. Please run fsck. Is there any other command on the linux terminal which I can use to safely eject the usb? so that the usb device is powered off before I unplug it.

Update: I tried using sync but the error is still there as shown below:

root@(none):~# sync root@(none):~# umount /media/sda1 root@(none):~# ls /media/sda1 root@(none):~# [ 296.021241] usb 2-1: USB disconnect, device number 3 [ 296.026879] sd 1:0:0:0: [sda] Synchronizing SCSI cache [ 296.031175] sd 1:0:0:0: [sda] [ 296.033743] Result: hostbyte=0x01 driverbyte=0x00 [ 296.048283] FAT-fs (sda1): unable to read boot sector to mark fs as dirty
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  • 2
    You could try sync. Commented Jun 17, 2016 at 6:47
  • Are there any side effects as It says here unix.stackexchange.com/questions/90657/… that 'sync is bad for lifetime of the device' and i am unsure about the side effects of flush Commented Jun 17, 2016 at 7:01
  • Bad or not - what's the effect of not syncing? Corrupt files. The article you linked to suggests that syncing each time you write to the device (for example after a few minutes of editing a document) is bad as you write too many times which in theory reduces the lifetime of the device. Syncing just before you umount is common sense as you want your data to be written to the device don't you? Commented Jun 17, 2016 at 7:08
  • as others mentioned, use sync before umount Commented Jun 17, 2016 at 7:23
  • 4
    FWIW, umount does a sync on the partition automatically. Commented Jun 17, 2016 at 11:26

1 Answer 1

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eject /dev/sda will try and safely remove the device from the kernel and make it safe to remove. You can verify it's removed by looking on /dev to see if the partition entry has been removed (the base device may still show up).

e.g. I just plugged in a USB stick and it showed as /dev/sdg and the partition as sdg1. I can unmount it and it still shows, but after the eject it disappears

$ ls /dev/sdg* /dev/sdg /dev/sdg1 $ df | grep sdg /dev/sdg1 59632764 47460364 9136496 84% /media/sweh/music $ umount /dev/sdg1 $ ls /dev/sdg* /dev/sdg /dev/sdg1 $ sudo eject /dev/sdg $ ls /dev/sdg* /dev/sdg
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  • my linux version apparently doesn't have that command root@(none):~# eject /dev/sda1 -sh: eject: command not found Commented Jun 17, 2016 at 11:38

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