How do I resolve `The following packages have unmet dependencies`

I was using this script to install basic software, but had to interrupt because of slow internet speed. Now when I hit $ sudo apt-get install npm , I get following error

yask123@yaskslaptop:~$ sudo apt-get installed npm
E: Invalid operation installed
yask123@yaskslaptop:~$ sudo apt-get install npm
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 npm : Depends: nodejs but it is not going to be installed
       Depends: node-abbrev (>= 1.0.4) but it is not going to be installed
       Depends: node-ansi (>= 0.3.0-2) but it is not going to be installed
       Depends: node-ansi-color-table but it is not going to be installed
       Depends: node-archy but it is not going to be installed
       Depends: node-block-stream but it is not going to be installed
       Depends: node-fstream (>= 0.1.22) but it is not going to be installed
       Depends: node-fstream-ignore but it is not going to be installed
       Depends: node-github-url-from-git but it is not going to be installed
       Depends: node-glob (>= 3.1.21) but it is not going to be installed
       Depends: node-graceful-fs (>= 2.0.0) but it is not going to be installed
       Depends: node-inherits but it is not going to be installed
       Depends: node-ini (>= 1.1.0) but it is not going to be installed
       Depends: node-lockfile but it is not going to be installed
       Depends: node-lru-cache (>= 2.3.0) but it is not going to be installed
       Depends: node-minimatch (>= 0.2.11) but it is not going to be installed
       Depends: node-mkdirp (>= 0.3.3) but it is not going to be installed
       Depends: node-gyp (>= 0.10.9) but it is not going to be installed
       Depends: node-nopt (>= 3.0.1) but it is not going to be installed
       Depends: node-npmlog but it is not going to be installed
       Depends: node-once but it is not going to be installed
       Depends: node-osenv but it is not going to be installed
       Depends: node-read but it is not going to be installed
       Depends: node-read-package-json (>= 1.1.0) but it is not going to be installed
       Depends: node-request (>= 2.25.0) but it is not going to be installed
       Depends: node-retry but it is not going to be installed
       Depends: node-rimraf (>= 2.2.2) but it is not going to be installed
       Depends: node-semver (>= 2.1.0) but it is not going to be installed
       Depends: node-sha but it is not going to be installed
       Depends: node-slide but it is not going to be installed
       Depends: node-tar (>= 0.1.18) but it is not going to be installed
       Depends: node-underscore but it is not going to be installed
       Depends: node-which but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Solution 1:

If sudo apt-get install -f <package-name> doesn't work, try aptitude:

sudo apt-get install aptitude
sudo aptitude install <package-name>

Aptitude will try to resolve the problem.

As an example, in my case, I still receive some error when try to install libcurl4-openssl-dev:

sudo apt-get install -f libcurl4-openssl-dev

So i try aptitude, it turns out I have to downgrade some packages.

The following actions will resolve these dependencies:

    Keep the following packages at their current version:
    1)     libyaml-dev [Not Installed]                        

Accept this solution? [Y/n/q/? (n)

The following actions will resolve these dependencies:

    Downgrade the following packages:                                
    1)     libyaml-0-2 [0.1.4-3ubuntu3.1 (now) -> 0.1.4-3ubuntu3 (trusty)]

Accept this solution? [Y/n/q/?] (Y)

Solution 2:

First of all try this

sudo apt-get update
sudo apt-get clean
sudo apt-get autoremove

If error still persists then do this

sudo apt --fix-broken install
sudo apt-get update && sudo apt-get upgrade
sudo dpkg --configure -a
sudo apt-get install -f

Afterwards try this again:

sudo apt-get install npm

But if it still couldn't resolve issues check for the dependencies using sudo dpkg --configure -a and remove them one-by-one . Let's say dependencies are on npm then go for this ,

sudo apt-get remove nodejs
sudo apt-get remove npm

Then go to /etc/apt/sources.list.d and remove any node list if you have. Then do a

sudo apt-get update

Then check for the dependencies problem again using sudo dpkg --configure -a and if it's all clear then you are done . Later on install npm again using this

v=8   # set to 4, 5, 6, ... as needed
curl -sL https://deb.nodesource.com/setup_$v.x | sudo -E bash -

Then install the Node.js package.

sudo apt-get install -y nodejs

The answer above will work for general cases also(for dependencies on other packages like django ,etc) just after first two processes use the same process for the package you are facing dependency with.

Solution 3:

The command to have Ubuntu fix unmet dependencies and broken packages is

sudo apt-get install -f

from the man page:

-f, --fix-broken Fix; attempt to correct a system with broken dependencies in place. This option, when used with install/remove, can omit any packages to permit APT to deduce a likely solution. If packages are specified, these have to completely correct the problem. The option is sometimes necessary when running APT for the first time; APT itself does not allow broken package dependencies to exist on a system. It is possible that a system's dependency structure can be so corrupt as to require manual intervention (which usually means using dselect(1) or dpkg --remove to eliminate some of the offending packages)

Ubuntu will try to fix itself when you run the command. When it completes, you can test if it worked by running the command again, and you should receive output similar to:

Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.

Solution 4:

Installing nodejs will install npm ... so just remove nodejs then reinstall it: $ sudo apt-get remove nodejs

$ sudo apt-get --purge remove nodejs node npm
$ sudo apt-get clean
$ sudo apt-get autoclean
$ sudo apt-get -f install
$ sudo apt-get autoremove