How to fix Error: operation was cancelled in Docker

The simplest fix for transient cancellation errors is restarting Docker Desktop:

On Windows/Mac:
1. Right-click the Docker Desktop icon in the system tray/menu bar
2. Select "Restart"
3. Wait for Docker Desktop to fully start (icon stops animating)

On Linux (systemd):

sudo systemctl restart docker

After restart, verify Docker is running:

docker info

If Docker Desktop shows "Docker Desktop stopped" repeatedly, proceed to the next steps.

Large build contexts with many files can cause cancellation during loading. Create or update your .dockerignore file:

# Create .dockerignore in your project root
touch .dockerignore

Add common directories that should be excluded:

# Dependencies
node_modules/
vendor/
.venv/
venv/
__pycache__/

# Build outputs
dist/
build/
target/
*.egg-info/

# IDE and editor files
.idea/
.vscode/
*.swp
*.swo

# Git
.git/
.gitignore

# Docker files (avoid recursive issues)
Dockerfile*
docker-compose*.yml

# Logs and temp files
*.log
tmp/
temp/

This significantly reduces the number of files Docker needs to process during build context creation.

IDEs like VS Code, RStudio, and JetBrains products can lock files, preventing Docker from accessing them during build:

Before running docker build:
1. Close your IDE completely (not just minimize)
2. Or run the docker command from an external terminal (not the IDE's integrated terminal)

For VS Code specifically:
- The file watcher and extensions may lock files during indexing
- Wait for VS Code to finish "restoring packages" or "indexing" before building
- Consider running docker build from Windows Terminal, PowerShell, or a separate command prompt

For RStudio:
- RStudio locks files it's using; close the project before building

This is especially important on Windows where file locking is more strict.

If you're running docker build from a different directory than your Dockerfile location, Docker may include unexpected files:

# Bad: Running from root while Dockerfile is in subdirectory
# This includes ALL files from current directory in build context
cd /
docker build -f /project/Dockerfile .

# Good: Run from the project directory
cd /project
docker build .

# Or specify the context explicitly
docker build -f /project/Dockerfile /project

An inflated build context causes longer loading times and potential cancellation:

# Check your build context size
du -sh . --exclude=.git

If the context is larger than expected, review what's being included.

If Docker Desktop is in an inconsistent state, resetting can resolve persistent issues:

On Windows:
1. Open Docker Desktop
2. Click the gear icon (Settings)
3. Navigate to "Troubleshoot"
4. Click "Reset to factory defaults"
5. Confirm and wait for Docker to restart

On Mac:
1. Click Docker Desktop in menu bar
2. Select Preferences > Troubleshoot
3. Click "Reset to factory defaults"

Alternative: Clean reset via command line (Windows):

# Stop Docker Desktop
Stop-Process -Name "Docker Desktop" -Force

# Remove Docker Desktop data
Remove-Item -Recurse -Force "$env:APPDATA\Docker"
Remove-Item -Recurse -Force "$env:LOCALAPPDATA\Docker"

# Restart Docker Desktop
Start-Process "C:\Program Files\Docker\Docker\Docker Desktop.exe"

Warning: This removes all containers, images, and volumes. Back up important data first.

On Windows, WSL2 integration issues can cause operation cancellations:

Update WSL2 kernel:

wsl --update

Restart WSL:

wsl --shutdown

Verify WSL2 is the default version:

wsl --set-default-version 2

Check Docker Desktop settings:
1. Open Docker Desktop Settings
2. Go to "General"
3. Ensure "Use the WSL 2 based engine" is checked

Edit settings.json if Docker Desktop won't start:

# Edit the settings file
notepad $env:APPDATA\Docker\settings.json

Ensure "wslEngineEnabled": true is set, then restart Docker Desktop.

Docker Desktop requires hardware virtualization and specific Windows features:

Check virtualization status:

# In PowerShell
systeminfo | findstr /i "virtualization"

If virtualization is disabled, enable it in BIOS:
1. Restart your computer and enter BIOS (usually F2, F10, Del, or Esc during boot)
2. Find "Virtualization Technology", "VT-x", or "AMD-V"
3. Enable it and save changes

Enable required Windows features:

# Enable Hyper-V (Windows Pro/Enterprise)
Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V -All

# Enable WSL
Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-Subsystem-Linux

# Enable Virtual Machine Platform
Enable-WindowsOptionalFeature -Online -FeatureName VirtualMachinePlatform

Restart your computer after enabling features.

If problems started after a Docker Desktop update, try an older version:

Download previous versions:
- Visit: https://docs.docker.com/desktop/release-notes/
- Or: https://desktop.docker.com/win/main/amd64/Docker%20Desktop%20Installer.exe (Windows)

Common stable versions to try:
- Docker Desktop 4.22.x (known stable for many users)
- Docker Desktop 4.19.x

Steps:
1. Uninstall current Docker Desktop
2. Download the older installer
3. Install the previous version
4. In Settings, disable automatic updates temporarily

# Uninstall via command line (Windows)
& "C:\Program Files\Docker\Docker\Docker Desktop Installer.exe" uninstall

After downgrading, verify the issue is resolved before re-enabling updates.

Resource exhaustion can cause operations to be cancelled:

# Check Docker disk usage
docker system df

# Remove unused data (safe cleanup)
docker system prune

# More aggressive cleanup (removes all unused images)
docker system prune -a

# Clean BuildKit cache specifically
docker builder prune --all

Check available disk space:

# Linux/Mac
df -h

# Windows PowerShell
Get-PSDrive C | Select-Object Used,Free

Ensure you have at least 10-20GB free for Docker operations. For Docker Desktop, you can also adjust the disk image size limit in Settings > Resources.