In my case, the following command in Terminal helped (as suggested by Günter Zöchbauer's comment):

killall -9 dart

On Windows, run the following in a Command Prompt or PowerShell window (as suggested by upupming's comment):

taskkill /F /IM dart.exe

(You can read about taskkill flags in Windows here)

Remove this file:

<YOUR FLUTTER FOLDER>/bin/cache/lockfile

This releases the occupied lock and makes you able to run other commands.

You can try to kill all flutter processes.

TL;DR - go to point 4)

1) List of the processes:

ps aux

2) Search name containing with flutter:

ps aux | grep flutter

where output can be like there:

stackoverflow 16697 1.5 0.0 4288316 704 ?? S 10:02PM 0:15.80 bash /flutter_path/flutter/bin/flutter --no-color build apk
stackoverflow 2800 1.5 0.0 4288316 704 ?? S 9:59PM 0:18.49 bash /flutter_path/flutter/bin/flutter --no-color pub get
stackoverflow 1215 1.5 0.0 4280124 700 ?? S 9:58PM 0:18.89 bash /flutter_path/flutter/bin/flutter --no-color config --machine
stackoverflow 8449 1.5 0.0 4296508 716 ?? S 10:00PM 0:17.20 bash /flutter_path/flutter/bin/flutter --no-color pub get
stackoverflow 1326 1.4 0.0 4288316 708 ?? S 9:58PM 0:18.97 bash /flutter_path/flutter/bin/flutter daemon
stackoverflow 16687 0.0 0.0 4279100 820 ?? S 10:02PM 0:00.01 bash /flutter_path/flutter/bin/flutter --no-color build apk
stackoverflow 8431 0.0 0.0 4288316 804 ?? S 10:00PM 0:00.02 bash /flutter_path/flutter/bin/flutter --no-color pub get
stackoverflow 2784 0.0 0.0 4288316 704 ?? S 9:59PM 0:00.01 bash /flutter_path/flutter/bin/flutter --no-color pub get
stackoverflow 1305 0.0 0.0 4280124 712 ?? S 9:58PM 0:00.01 bash /flutter_path/flutter/bin/flutter daemon
stackoverflow 1205 0.0 0.0 4279100 788 ?? S 9:58PM 0:00.01 bash /flutter_path/flutter/bin/flutter --no-color config --machine
stackoverflow 11416 0.0 0.0 4268176 536 s000 R+ 10:18PM 0:00.00 grep --color flutter

3) Get processes ID

We need content from second column (from above output):

ps aux | grep flutter | awk '{print 2ドル}'

4 a) Kill "automatically":

To list, search and kill all of them you can use

kill $(ps aux | grep flutter | grep -v grep | awk '{print 2ドル}')

(you can run it also with sudo)

or

ps aux | grep flutter | grep -v grep | awk '{print 2ドル}' | xargs kill -15

4 b) Kill manually

You can kill processes one-by-one using:

sudo kill -15 <process_ID>

e.g. to kill process with id 13245 use:

sudo kill -15 13245

If -15 will not work, you can try -2 or -1.

Final option it is -9 which should not be used because it prevents the process from doing any cleanup work.

I use a Mac with Visual Studio Code and this is what worked:

Shutdown your PC and switch it on again. Don't use the restart function. I restarted 2 times and it didn't work. Only shutdown worked.

PS: I tried out the following:

1. Delete lockfile;
2. Run killall -9 dart;
3. Restart my PC.

But they all didn't work.

In Windows :

Press: Ctrl + Alt + Delete

• In task manager find out your editor such as VS Studio or Android Studio
• In that Find "dart" and End that Task
• Then close your editor
• Open editor again
• let editor to complete all things, after that run your query that will work

Most are saying killall -9 dart but nobody mentioned pkill -f dart which worked for me.

The difference between the 2 is explained here.

Exit from your IDE, then from start manager stop all dart related files(if any have).
Then go to
"FLUTTER DIRECTORY"/bin/cache/lockfile
and delete this lockfile

I have the same issue, I tried all the above solutions, but none of them worked for me. Then I searched the keywords in flutter directory, and found the following code. So I tried to delete bin/cache/.upgrade_lock, and it worked finally.

enter image description here

I have tried all of below steps, but none worked.

1. Delete lockfile;
2. Run killall -9 dart;
3. Restart my PC.

Below is the final command that worked for me

rm -rf <flutter_dir>bin/cache/.upgrade_lock

This also happens when you have opened the flutter project in the Editor. Close the Editor and re-run the command

I tried all previous suggestions but without benefit. Finally when I connect my pc to internet and wait flutter to release then 5 minutes solved

In VS code run

flutter clean

in the terminal. This fixed my issue.

code image

I tried all the previous suggestions but no one solved the problem.. I did the following and it works (Windows 11):

1. run command: taskkill /F /IM dart.exe in TERMINAL in VS code.
2. close VS code.
3. delete lockfile in <flutter_SDK_bath>\bin\cache.
4. restart computer.
5. run command: flutter doctor in Power Shell. (especially after updating flutter SDk).
6. run command flutter pub get in application path.

that's works for me..

For me, this problem occurred when I downloaded and replaced the new version of Flutter. After searching for a long time, I realized that nothing should be done. At this moment, Android Studio is processing new files and folders. This message will be removed after approximately 4 minutes.

1. Delete pubspec.lock file
2. Run "flutter pub get" from terminal or editor shortcut ("get packages" AndroidStudio or this logo Visual Studio) in pubspec.yaml file.
3. Wait for download.
4. If it doesn't work relaunch your editor then repeat step 2..

For me, the issue's root cause on my Mac device was a version of the flock binary it was not expecting. Removing it from the path did the trick; probably a BSD vs GNU syntax issue.

In 🍏 MacOS terminal run:

ps

If you see flutter or dart related process like this:

 PID TTY TIME CMD
 8166 ttys000 0:00.14 -zsh
 8199 ttys000 0:00.00 bash /Users/sabrina/devtools/flutter/bin/flutter zsh-completion
 8212 ttys000 0:00.00 bash /Users/sabrina/devtools/flutter/bin/flutter zsh-completion
 8222 ttys000 0:00.00 bash /Users/sabrina/devtools/flutter/bin/internal/update_dart_sdk.sh

Kill them using kill [PID] command, for example:

kill 8222

1. Turn off Android Studio.

2. Open flutter installation directory /bin/cache.

3. Delete lockfile.

4. At this point, you can execute the flutter related command on the command line to solve the problem perfectly.

You can remove flutter and "install again", so fastest way is to:

1) Check where you have flutter (as executable)

To check it, you can run:

which flutter

And you can expect such output:

/your_user/your_path/flutter/bin/flutter

2) Go to this directory

Above path is directly to flutter, but we would like to go to directory so "one earlier" in path:

cd /your_user/your_path/flutter/bin

3) Check is it git repository

It should be, but it's worth to check.

Run one of the git command e.g.

git status

or

git branch

When it's git repository you will receive some info about it or correct list of branches.

4) Remove all of the files

rm -R *

5) "revert" removal to have only necessary files:

git co -- .

6) Voila!

You can run just flutter version and commands should work (and Flutter will fetch some necessary data).

If you are using Windows, you can open the task manager and under the 'Processes' tab search for processes named 'dart'. End all those tasks.

In Android Studio, It's Work for me

Stop your app if it still runs on the phone or disconnect the your testing device.

Then try to install the package again.

There are some action to do:

1- in pubspec.yaml press "packages get" or in terminal type " flutter packages get" and wait seconds.

if this doesn't work :

2-type flutter clean then do step(1)

if this doesn't work too :

3-type killtask /f /im dart.exe

if this doesn't work too :

4- close android studio and then restart your pc.

Nothing of ALL these answers didn't helped me.

The only one solution was to remove whole flutter stuff (and reinstall flutter from git):

<flutter directory>
<user>/.flutter_tool_state
<user>/.dart
<user>/.pub-cache
<user>/.dartServer
<user>/.flutter

Restart your computer or simple logout from the current user and login again.

i had same issue , in terminal executed this command

taskkill /F /IM dart.exe

and Flutter Clean , Flutter pub get then restarted the pc and it worked.

• In the terminal type flutter packages get
• Type flutter clean

If it doesn't work do this:

• Type killtask /f /im dart.exe.

Close Android Studio and then restart your PC.

I tried most of the answers here, but what I believe is happening is that there is some hidden dart process running when you open any app like VSCode or Android Studio. My steps were a lot simpler to solve this:

• Shut off your computer (don't just restart it) and turn it back on
• Don't open VSCode or Android Studio
• If there's any dart process running, kill it with task manager or with the commands provided by the folks here
• Go to {FlutterDirectory}/bin/cache and delete everything there (it's just cache so doesn't matter)
• Open terminal
• Run flutter clean

I believe the flutter/dart extension for VSCode might lock it if you try to run flutter clean in VSCode, but you can try it

For my case i was not connected to the internet and if you have setup a firewall just allow dart to connect.

For Windows users, the best option that worked for me was to end the dart task from the Task Manager. Here's a screenshot below: end all the dart task

After trying most of the things above and none works, what i did was to just move the flutter folder from the path to bin, and then replace it back and it works.

• flutter
• command
• lockfile