Unable to lock the administration directory (/var/lib/dpkg/) error when trying to install unrar from the terminal in Ubuntu

Question

I am getting this error when trying to install unrar unarchiver for .rar files from the terminal in Ubuntu.

E: Could not open lock file /var/lib/dpkg/lock - open (2: No such file or directory)
E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?

Answer 1

Run the following command :

sudo rm /var/lib/dpkg/lock

Create missing folders (use the command ls -l /var/lib/dpkg/ first to display the existing folders, if somes floders exist do not re-create it agin):

sudo mkdir -p /var/lib/dpkg/{alternatives,info,parts,triggers,updates,methods,available,diversions}

Move dpkg.status.0 and repair the base file:

sudo cp /var/backups/dpkg.status.0 /var/lib/dpkg/status
sudo apt-get download dpkg
sudo dpkg -i dpkg*.deb
sudo apt-get download base-files
sudo dpkg -i base-files*.deb
sudo apt update && sudo apt upgrade

Check and repair broken dependencies:

sudo apt-get check
sudo apt -f install

Answer 2

• The error message is asking if you are root in order to be permitted to run a command to install software from the terminal. Use sudo before a command to run the command with root privileges, like this:

  sudo apt install example-package  
  

  This example command installs a package named example-package.

• If you still get a lock error, close the Ubuntu Software Center (Ubuntu 14.04) or Software application (Ubuntu 16.04) and the terminal to unlock /var/lib/dpkg/, reopen the terminal and try the command again.

• If you still get a lock error, run this command to show details about the locking process.

  ps -e | grep -e apt -e adept | grep -v grep  
  

  Then open the System Monitor application and kill the process that has the same process ID as the results of the previous command.

---

For the error mentioned in the comment:

Errors were encountered while processing: /var/cache/apt/archives/libgtk-3-bin_3.18.9-1ubuntu3.1_amd64.deb   
E: Sub-process /usr/bin/dpkg returned an error code (1)  

Try fixing it by running these commands:

sudo apt-get clean  
sudo apt update  
sudo apt upgrade  
sudo dpkg --configure -a  
sudo apt-get -f install  

Then try running the command that resulted in the error message again.

Answer 3

Run the command below to generate a list of all processes whose name comprises of the word apt, you will get a list inclusive of all apt or apt-get processes by using ps and grep commands together with a pipeline.

ps -A | grep apt

For each apt-get or apt process that you can see in the output of the command above, kill each process using the command below.

The process ID (PID) is found in the first column from the screenshot above.

sudo kill -9 processnumber
or
sudo kill -SIGKILL processnumber

For instance, in the command below where 9 is the signal number for the SIGKILL signal, will kill the first apt process:

sudo kill -9 13431
or
sudo kill -SIGKILL 13431

First execute the command below to remove the lock file in the /var/lib/dpkg/ directory:

sudo rm /var/lib/dpkg/lock

Afterwards force package(s) to reconfigure like so:

sudo dpkg --configure -a

Alternatively, delete the lock files in the /var/lib/apt/lists/ and cache directory as below:

sudo rm /var/lib/apt/lists/lock
sudo rm /var/cache/apt/archives/lock

Next, update your packages sources list as follows:

sudo apt update
or
sudo apt-get update

Full info https://www.tecmint.com/fix-unable-to-lock-the-administration-directory-var-lib-dpkg-lock/