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I want to know the exact process that is using the lock file. I don't want to fix it, but just to know what is my system doing. How can I find out?

For example, this message:

E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)
E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?

Again, I just want to identify the process using it, not how to fix it.

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up vote 14 down vote accepted

There is the infamous lsof:

sudo lsof /var/lib/dpkg/lock
aptitude 4974 root    3uW  REG   8,23        0 815673 /var/lib/dpkg/lock

In this case aptitude is using the file. You should use root in case you are not sure which user is locking the file. It's useful for a bunch of things too, sadly it doesn't come installed with Ubuntu, so you have to install it first.

For the rest of mortals, there's the fuser command. This is peculiar since it only returns the PID instead of the name of the process:

➜  ~  sudo fuser /var/lib/dpkg/lock
/var/lib/dpkg/lock:   4974

Here it says that the file and PID, which is 4974, so we must investigate who is:

➜  ~  ps 4974
 4974 pts/1    Sl+    0:06 aptitude
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Why is lsof infamous? Are there some problems with it? – Ruslan Jan 19 '14 at 9:29
@Ruslan Yeah, it allows clueless users know the actual usage of the systems contrary to what the sysadmins wants... – Braiam Jan 19 '14 at 11:09
@Braiam Too much information can be a dangerous thing, in the right hands? ^-_-^ – Peter David Carter May 7 at 16:27

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