a start job is running for dev-disk-by

Recently, I encountered a strange problem when booting up my Linux OS.

a start job is running for dev-disk-by uuid <disk-partition-uuid>

This process lasts for 1 minute and 30s ! OMG! That’s unbearable. And then it told me:

Timed out waiting for device dev-disk-by\<disk-partition-uuid>
Denpendency failed for /dev/disk/by-uuid/<disk-partition-uuid>
Denpendency failed for Swap

Take a look at the third line. As you can clearly see, the disk partition causing this problem is the swap partition.

After my Linux OS booted into desktop, I opened up a terminal and check my swap partition with this command:

swapon --show

a start job is running for dev-disk-by

As you can see from the screenshot, my swap partition wasn’t activated. I also issued the following command to check mounted partitions and my swap partition wasn’t there.


So why did swap partition fail to mount on system boot time? As I later found out, the UUID of my swap partition has changed. Enter this command to check the real UUID of swap partition.

sudo blkid

then check the UUID of swap partition in /etc/fstab.

sudo nano /etc/fstab

If the two UUIDs are different, then the /etc/fstab file is corrupted and you need to replace the UUID in /etc/fstab with the UUID returned by sudo blkid.

Save and close /etc/fstab file. Reboot your computer.

Now the “a start job is running for dev-disk-by” message was gone and you saved 1 minute and 30s of your life.

The same error occurred on my Arch Linux, Fedora and Ubuntu machine. One thing I don’t like about Ubuntu is that it veils system messages with its logo when booting up. For a long time I did’t know why it takes such a long time for Ubuntu to boot into Unity desktop. Finally I found the reason.

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