Batch Command Execution¶

Execute shell commands across multiple VMs simultaneously with parallel execution and aggregated output.

Overview¶

azlin batch command runs any shell command on multiple VMs at once, displaying aggregated results. Perfect for fleet-wide updates, health checks, and rapid diagnostics across your entire VM infrastructure.

Basic Usage¶

# Execute on VMs with specific tag
azlin batch command 'uptime' --tag env=dev

# Execute on VMs matching pattern
azlin batch command 'df -h' --vm-pattern 'web-*'

# Execute on all VMs
azlin batch command 'hostname' --all

# Show output from each VM
azlin batch command 'ps aux | grep python' --all --show-output

Command Options¶

Option	Description	Default
`--tag`	Filter VMs by tag (key=value)	None
`--vm-pattern`	Filter VMs by name glob	None
`--all`	Select all VMs	False
`--show-output`	Show command output from each VM	False
`--max-workers`	Parallel execution threads	10
`--timeout`	Command timeout in seconds	300
`--resource-group`, `--rg`	Resource group	Current context

Examples¶

Fleet Health Check¶

azlin batch command 'uptime' --all --show-output

Output:

[web-1] 14:23:45 up 5 days, 2:15, 1 user, load average: 0.52, 0.45, 0.38
[web-2] 14:23:46 up 5 days, 2:16, 1 user, load average: 0.15, 0.20, 0.18
[db-1]  14:23:47 up 12 days, 8:42, 1 user, load average: 1.25, 1.30, 1.28

Completed: 3/3 VMs

Update Packages on Development VMs¶

azlin batch command 'sudo apt update && sudo apt upgrade -y' \
  --tag env=dev \
  --timeout 600

Check Disk Space¶

azlin batch command 'df -h /' --all --show-output

Restart Service on Web Servers¶

azlin batch command 'sudo systemctl restart nginx && systemctl status nginx' \
  --vm-pattern 'web-*' \
  --show-output

Run Custom Script¶

azlin batch command 'bash /tmp/deploy.sh' \
  --tag project=myapp \
  --timeout 1800

Common Use Cases¶

1. Package Updates¶

# Update all dev VMs
azlin batch command 'sudo apt update && sudo apt upgrade -y' \
  --tag env=dev \
  --timeout 900

# Install new package fleet-wide
azlin batch command 'sudo apt install -y htop' --all

2. Configuration Deploy¶

# Restart after config change
azlin batch command 'sudo systemctl restart app && systemctl status app' \
  --vm-pattern 'app-*' \
  --show-output

3. Health Checks¶

# Check service status
azlin batch command 'systemctl is-active nginx' --vm-pattern 'web-*' --show-output

# Check disk usage
azlin batch command 'df -h' --all --show-output

# Check memory
azlin batch command 'free -h' --all --show-output

4. Log Collection¶

# Grab recent errors
azlin batch command 'tail -50 /var/log/app.log | grep ERROR' \
  --all \
  --show-output > errors.log

5. Security Updates¶

# Apply security patches
azlin batch command 'sudo unattended-upgrade' \
  --all \
  --timeout 1200

Parallelism and Performance¶

Default Behavior¶

10 concurrent SSH connections
Queue remaining VMs
Continue on individual failures

Adjust for Your Workload¶

# Light operations: high parallelism
azlin batch command 'hostname' --all --max-workers 20

# Heavy operations: low parallelism
azlin batch command 'docker build .' --all --max-workers 3

Output Handling¶

Without --show-output¶

Shows only summary:

Executing on 5 VMs...
Completed: 5/5 VMs

With --show-output¶

Shows output from each VM:

[vm-1] Command output here
[vm-2] Command output here
Completed: 2/2 VMs

Error Handling¶

Failed VMs don't stop execution
Summary shows successful/failed counts
Exit code reflects any failures

Tips¶

Test on one VM first: Use --vm-pattern 'vm-1' to test
Use timeouts: Set realistic timeouts for long operations
Capture output: Use --show-output > file.log to save results
Escape properly: Use single quotes for commands with special characters