bootc-docs/exec-in-host-mount-namespace/bootc-exec-in-host-mount-namespace-quick-reference.md

# bootc exec-in-host-mount-namespace - Quick Reference

## Command Summary

| Command | Purpose | Usage |
|---------|---------|-------|
| `exec-in-host-mount-namespace` | Execute command in host mount namespace | `bootc exec-in-host-mount-namespace [ARGS]...` |

## Quick Commands

### Basic Operations
```bash
# Execute command in host mount namespace
bootc exec-in-host-mount-namespace ls /

# Execute with arguments
bootc exec-in-host-mount-namespace mount /dev/sda1 /mnt

# Execute system command
bootc exec-in-host-mount-namespace systemctl status
```

### System Operations
```bash
# Check host filesystem
bootc exec-in-host-mount-namespace df -h

# View host processes
bootc exec-in-host-mount-namespace ps aux

# Check host system status
bootc exec-in-host-mount-namespace systemctl status
```

### Installation Operations
```bash
# Create directories in host filesystem
bootc exec-in-host-mount-namespace mkdir -p /var/lib/bootc

# Copy files to host filesystem
bootc exec-in-host-mount-namespace cp /source/file /host/destination/

# Set permissions
bootc exec-in-host-mount-namespace chmod 644 /host/file
```

## Common Options

| Option | Purpose | Example |
|--------|---------|---------|
| `--help` | Show help | `bootc exec-in-host-mount-namespace --help` |
| `--verbose` | Verbose output | `bootc exec-in-host-mount-namespace -v ls /` |
| `--quiet` | Quiet output | `bootc exec-in-host-mount-namespace -q ls /` |

## Error Codes

| Code | Meaning | Solution |
|------|---------|----------|
| 1 | General error | Check logs for details |
| 2 | Missing command | Provide command to execute |
| 3 | Namespace access error | Check /proc/1/ns/mnt exists |
| 4 | setns error | Run as root |
| 5 | Command not found | Use full path to command |

## Common Issues

### Missing Command
```bash
# Error: Missing command
# Solution: Provide a command
bootc exec-in-host-mount-namespace ls /

# Or use a shell
bootc exec-in-host-mount-namespace /bin/bash
```

### Namespace Access Error
```bash
# Error: open pid1 mountns: No such file or directory
# Solution: Check if /proc/1/ns/mnt exists
ls -la /proc/1/ns/mnt

# Run as root
sudo bootc exec-in-host-mount-namespace ls /
```

### setns Error
```bash
# Error: setns: Operation not permitted
# Solution: Run as root
sudo bootc exec-in-host-mount-namespace ls /

# Check capabilities
getcap /usr/bin/bootc
```

### Command Not Found
```bash
# Error: exec: command not found
# Solution: Use full path
bootc exec-in-host-mount-namespace /bin/ls /

# Check command availability
bootc exec-in-host-mount-namespace which ls
```

## Environment Variables

| Variable | Purpose | Default |
|----------|---------|---------|
| `RUST_LOG` | Log level | `info` |
| `BOOTC_DEBUG` | Debug mode | `false` |
| `BOOTC_CONFIG` | Config file | `/etc/bootc/config.toml` |

## Configuration Files

| File | Purpose | Location |
|------|---------|----------|
| Main config | Bootc configuration | `/etc/bootc/config.toml` |
| Namespace info | Namespace information | `/proc/1/ns/mnt` |
| Process info | Process information | `/proc/self/ns/mnt` |

## Log Files

| File | Purpose | Location |
|------|---------|----------|
| System logs | System messages | `/var/log/messages` |
| Journal logs | Systemd journal | `journalctl -u bootc-*` |
| Bootc logs | Bootc specific | `/var/log/bootc/` |

## Performance Tips

### Optimize Operations
```bash
# Check system load
uptime

# Check memory usage
free -h

# Check namespace overhead
time bootc exec-in-host-mount-namespace /bin/true
time /bin/true
```

### Monitor System
```bash
# Check namespace availability
ls -la /proc/1/ns/mnt

# Check namespace differences
diff /proc/1/ns/mnt /proc/self/ns/mnt

# Check system performance
bootc exec-in-host-mount-namespace top -bn1 | head -20
```

## Security Considerations

### Root Privileges
- All exec-in-host-mount-namespace commands require root privileges
- Use `sudo` or switch to root user
- Check current user with `whoami`

### Namespace Access
- Command accesses host mount namespace through `/proc/1/ns/mnt`
- Requires appropriate privileges for namespace switching
- Uses `setns` system call for namespace switching

### Process Isolation
- Command executes in host mount namespace
- Current process is replaced with target command
- Provides access to host filesystem view

## Best Practices

### Regular Operations
- Use only when host mount namespace access is needed
- Check command availability before execution
- Implement proper error handling
- Monitor system performance

### Development
- Use in container environments
- Test commands before production use
- Document procedures
- Monitor system health

### Production
- Set up monitoring
- Configure alerts
- Regular testing
- Document procedures

## Troubleshooting Steps

1. **Check command availability**
   ```bash
   bootc exec-in-host-mount-namespace which <command>
   ```

2. **Check namespace availability**
   ```bash
   ls -la /proc/1/ns/mnt
   ```

3. **Check privileges**
   ```bash
   whoami
   sudo bootc exec-in-host-mount-namespace <command>
   ```

4. **Check logs**
   ```bash
   journalctl -u bootc-* --since "1 hour ago"
   tail -f /var/log/bootc/main.log
   ```

5. **Test command execution**
   ```bash
   bootc exec-in-host-mount-namespace /bin/true
   ```

## Quick Scripts

### Health Check
```bash
#!/bin/bash
bootc exec-in-host-mount-namespace /bin/true && echo "System healthy"
```

### Namespace Test
```bash
#!/bin/bash
bootc exec-in-host-mount-namespace ls / && echo "Namespace access OK"
```

### Command Test
```bash
#!/bin/bash
bootc exec-in-host-mount-namespace which "$1" && echo "Command available"
```

### System Check
```bash
#!/bin/bash
bootc exec-in-host-mount-namespace uname -a && echo "System check OK"
```

## Integration Examples

### Systemd Service
```bash
# Create service file
cat > /etc/systemd/system/bootc-exec-in-host-mount-namespace.service << EOF
[Unit]
Description=Bootc Exec in Host Mount Namespace Service
After=multi-user.target

[Service]
Type=oneshot
ExecStart=/usr/local/bin/bootc-exec-in-host-mount-namespace-script.sh
User=root
Group=root

[Install]
WantedBy=multi-user.target
EOF

# Enable service
systemctl daemon-reload
systemctl enable bootc-exec-in-host-mount-namespace.service
```

### Cron Job
```bash
# Add to crontab
echo "0 2 * * * /usr/local/bin/bootc-exec-in-host-mount-namespace-maintenance.sh" | crontab -
```

### Monitoring
```bash
# Check system health
if ! bootc exec-in-host-mount-namespace /bin/true > /dev/null 2>&1; then
    echo "WARNING: Exec-in-host-mount-namespace failed"
    # Send alert
fi
```

This quick reference provides essential information for using the bootc exec-in-host-mount-namespace system effectively.