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Pterodactyl Wings provides comprehensive file management capabilities for game servers, including direct file operations, SFTP access, and disk quota enforcement. The filesystem implementation is designed for security, performance, and safety.

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Filesystem Architecture

Each server has its own isolated filesystem instance that wraps a Unix filesystem implementation.

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Filesystem Structure

// From server/filesystem/filesystem.go:24-34
type Filesystem struct {
    unixFS *ufs.Quota
    
    mu                sync.RWMutex
    lastLookupTime    *usageLookupTime
    lookupInProgress  atomic.Bool
    diskCheckInterval time.Duration
    denylist          *ignore.GitIgnore
    
    isTest bool
}
Key Components:
  • unixFS - Core Unix filesystem with quota tracking
  • denylist - Files/patterns that cannot be modified (egg-defined)
  • lastLookupTime - Tracks disk usage calculation timing
  • lookupInProgress - Prevents concurrent disk scans

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Initialization

// From server/filesystem/filesystem.go:37-54
func New(root string, size int64, denylist []string) (*Filesystem, error) {
    if err := os.MkdirAll(root, 0o755); err != nil {
        return nil, err
    }
    
    unixFS, err := ufs.NewUnixFS(root, config.UseOpenat2())
    if err != nil {
        return nil, err
    }
    
    quota := ufs.NewQuota(unixFS, size)
    
    return &Filesystem{
        unixFS:            quota,
        diskCheckInterval: time.Duration(config.Get().System.DiskCheckInterval),
        lastLookupTime:    &usageLookupTime{},
        denylist:          ignore.CompileIgnoreLines(denylist...),
    }, nil
}
Path Convention: 
/var/lib/pterodactyl/volumes/{server-uuid}/
Each server gets its own directory under the configured data path.

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File Operations

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Reading Files

Files are accessed through the filesystem wrapper for safety: 
// From server/filesystem/filesystem.go:75-86
func (fs *Filesystem) File(p string) (ufs.File, Stat, error) {
    f, err := fs.unixFS.Open(p)
    if err != nil {
        return nil, Stat{}, err
    }
    
    st, err := statFromFile(f)
    if err != nil {
        _ = f.Close()
        return nil, Stat{}, err
    }
    
    return f, st, nil
}
This returns both a file handle and stat information in one operation.

​
Writing Files

File writes include automatic quota checking: 
// From server/filesystem/filesystem.go:140-187
func (fs *Filesystem) Write(p string, r io.Reader, newSize int64, mode ufs.FileMode) error {
    var currentSize int64
    
    // Get current file size if it exists
    st, err := fs.unixFS.Stat(p)
    if err != nil && !errors.Is(err, ufs.ErrNotExist) {
        return errors.Wrap(err, "failed to stat file")
    } else if err == nil {
        if st.IsDir() {
            return errors.WithStack(&Error{code: ErrCodeIsDirectory})
        }
        currentSize = st.Size()
    }
    
    // Check that the new size can fit
    if err := fs.HasSpaceFor(newSize - currentSize); err != nil {
        return err
    }
    
    // Create or truncate the file
    file, err := fs.unixFS.Touch(p, ufs.O_RDWR|ufs.O_TRUNC, mode)
    if err != nil {
        return err
    }
    defer file.Close()
    
    if newSize == 0 {
        // Subtract the previous size
        fs.unixFS.Add(-currentSize)
    } else {
        // Copy data with limit
        var n int64
        n, err = io.Copy(file, io.LimitReader(r, newSize))
        
        // Adjust disk usage
        fs.unixFS.Add(n - currentSize)
    }
    
    // Set correct ownership
    if err := fs.chownFile(p); err != nil {
        return err
    }
    
    return err
}
Write Process:
  1. Check current file size (if exists)
  2. Verify new size fits within quota
  3. Create/truncate file
  4. Copy data (limited to newSize)
  5. Update quota tracking
  6. Fix file ownership

​
Creating Directories

// From server/filesystem/filesystem.go:190-193
func (fs *Filesystem) CreateDirectory(name string, p string) error {
    return fs.unixFS.MkdirAll(filepath.Join(p, name), 0o755)
}
Directories are created with parent directories as needed.

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Copying Files

The copy operation creates a uniquely named duplicate: 
// From server/filesystem/filesystem.go:302-362
func (fs *Filesystem) Copy(p string) error {
    dirfd, name, closeFd, err := fs.unixFS.SafePath(p)
    defer closeFd()
    if err != nil {
        return err
    }
    
    source, err := fs.unixFS.OpenFileat(dirfd, name, ufs.O_RDONLY, 0)
    if err != nil {
        return err
    }
    defer source.Close()
    
    info, err := source.Stat()
    if err != nil {
        return err
    }
    
    if info.IsDir() || !info.Mode().IsRegular() {
        return ufs.ErrNotExist
    }
    
    currentSize := info.Size()
    
    // Check quota
    if err := fs.HasSpaceFor(currentSize); err != nil {
        return err
    }
    
    // Generate copy name ("file.txt" -> "file copy.txt")
    base := info.Name()
    extension := filepath.Ext(base)
    baseName := strings.TrimSuffix(base, extension)
    
    // Handle .tar.gz style extensions
    if strings.HasSuffix(baseName, ".tar") {
        extension = ".tar" + extension
        baseName = strings.TrimSuffix(baseName, ".tar")
    }
    
    newName, err := fs.findCopySuffix(dirfd, baseName, extension)
    if err != nil {
        return err
    }
    
    dst, err := fs.unixFS.OpenFileat(dirfd, newName, ufs.O_WRONLY|ufs.O_CREATE, info.Mode())
    if err != nil {
        return err
    }
    
    n, err := io.Copy(dst, io.LimitReader(source, currentSize))
    fs.unixFS.Add(n)
    
    // Fix ownership
    if !fs.isTest {
        fs.unixFS.Lchownat(dirfd, newName, config.Get().System.User.Uid, config.Get().System.User.Gid)
    }
    
    return err
}
Copy Naming:
  • file.txt → file copy.txt
  • file copy.txt → file copy 2.txt
  • file copy 2.txt → file copy 3.txt
  • After 50 attempts: file copy.2026-03-04T10:30:00Z.txt

​
Deleting Files

// From server/filesystem/filesystem.go:390-392
func (fs *Filesystem) Delete(p string) error {
    return fs.unixFS.RemoveAll(p)
}
Deletion removes files or entire directory trees.

​
Renaming Files

// From server/filesystem/filesystem.go:195-197
func (fs *Filesystem) Rename(oldpath, newpath string) error {
    return fs.unixFS.Rename(oldpath, newpath)
}

​
File Permissions

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Ownership Management

All files must be owned by the configured Wings user: 
// From server/filesystem/filesystem.go:203-211
func (fs *Filesystem) chownFile(name string) error {
    if fs.isTest {
        return nil
    }
    
    uid := config.Get().System.User.Uid
    gid := config.Get().System.User.Gid
    return fs.unixFS.Lchown(name, uid, gid)
}

​
Recursive Ownership

The Chown function recursively sets ownership: 
// From server/filesystem/filesystem.go:217-259
func (fs *Filesystem) Chown(p string) error {
    if fs.isTest {
        return nil
    }
    
    uid := config.Get().System.User.Uid
    gid := config.Get().System.User.Gid
    
    dirfd, name, closeFd, err := fs.unixFS.SafePath(p)
    defer closeFd()
    if err != nil {
        return err
    }
    
    // Chown the initial path
    if err := fs.unixFS.Lchownat(dirfd, name, uid, gid); err != nil {
        return errors.Wrap(err, "failed to chown path")
    }
    
    // Check if it's a directory
    if st, err := fs.unixFS.Lstatat(dirfd, name); err != nil || !st.IsDir() {
        return nil
    }
    
    // Walk and chown everything inside
    if err := fs.unixFS.WalkDirat(dirfd, name, func(dirfd int, name, _ string, info ufs.DirEntry, err error) error {
        if err != nil {
            return err
        }
        if err := fs.unixFS.Lchownat(dirfd, name, uid, gid); err != nil {
            return err
        }
        return nil
    }); err != nil {
        return fmt.Errorf("failed to chown during walk: %w", err)
    }
    
    return nil
}
Performance Optimization: The walker uses an internally reused buffer and direct syscalls via dirfd, making it highly efficient for large directory trees.

​
Permission Modes

File modes can be changed: 
// From server/filesystem/filesystem.go:261-263
func (fs *Filesystem) Chmod(path string, mode ufs.FileMode) error {
    return fs.unixFS.Chmod(path, mode)
}

​
Directory Listing

Listing directories returns enriched stat information: 
// From server/filesystem/filesystem.go:423-490
func (fs *Filesystem) ListDirectory(p string) ([]Stat, error) {
    // Read entries and map to Stat
    out, err := ufs.ReadDirMap(fs.unixFS.UnixFS, p, func(e ufs.DirEntry) (Stat, error) {
        info, err := e.Info()
        if err != nil {
            return Stat{}, err
        }
        
        // Determine mimetype
        var d string
        if e.Type().IsDir() {
            d = "inode/directory"
        } else {
            d = "application/octet-stream"
        }
        
        var m *mimetype.MIME
        if e.Type().IsRegular() {
            // Detect mimetype from file content
            eO := e.(interface {
                Open() (ufs.File, error)
            })
            f, err := eO.Open()
            if err != nil {
                return Stat{}, err
            }
            m, err = mimetype.DetectReader(f)
            if err != nil {
                log.Error(err.Error())
            }
            _ = f.Close()
        }
        
        st := Stat{FileInfo: info, Mimetype: d}
        if m != nil {
            st.Mimetype = m.String()
        }
        return st, nil
    })
    if err != nil {
        return nil, err
    }
    
    // Sort alphabetically
    slices.SortStableFunc(out, func(a, b Stat) int {
        switch {
        case a.Name() == b.Name():
            return 0
        case a.Name() > b.Name():
            return 1
        default:
            return -1
        }
    })
    
    // Sort folders first
    slices.SortStableFunc(out, func(a, b Stat) int {
        switch {
        case a.IsDir() && b.IsDir():
            return 0
        case a.IsDir():
            return -1
        default:
            return 1
        }
    })
    
    return out, nil
}
Returned Information:
  • File name
  • File size
  • Modification time
  • Permissions
  • Mimetype (detected from content)
  • Is directory
Sorting Order:
  1. Directories before files
  2. Alphabetically within each group

​
Disk Quota Management

Wings enforces disk quotas by tracking usage in memory and performing periodic recalculations.

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Quota Structure

The quota system wraps the Unix filesystem: 
type Quota struct {
    *UnixFS
    limit int64        // Quota limit in bytes
    usage atomic.Int64 // Current usage
}

​
Quota Checking

Before writing files, quota is checked: 
func (fs *Filesystem) HasSpaceFor(size int64) error {
    if fs.unixFS.Limit() <= 0 {
        // Unlimited quota
        return nil
    }
    
    current := fs.unixFS.Usage()
    limit := fs.unixFS.Limit()
    
    if current + size > limit {
        return &Error{
            code: ErrCodeDiskSpace,
        }
    }
    
    return nil
}

​
Usage Tracking

Usage is updated atomically after operations: 
// From server/filesystem/filesystem.go:131
fs.unixFS.Add(n - currentSize)
The Add method uses atomic operations: 
func (q *Quota) Add(delta int64) {
    q.usage.Add(delta)
}

​
Usage Recalculation

Periodic full scans ensure accuracy: 
func (fs *Filesystem) HasSpaceAvailable(triggerLookup bool) bool {
    // Check if we should trigger a lookup
    if triggerLookup {
        // Only one lookup at a time
        if fs.lookupInProgress.CompareAndSwap(false, true) {
            defer fs.lookupInProgress.Store(false)
            
            // Calculate actual disk usage
            size, err := fs.DirectorySize("/")
            if err != nil {
                return true  // Assume space available on error
            }
            
            // Update tracked usage
            fs.unixFS.SetUsage(size)
            fs.lastLookupTime.Store(time.Now())
        }
    }
    
    // Check quota
    return fs.unixFS.Usage() < fs.unixFS.Limit()
}
Recalculation Triggers:
  • Server start (if data directory exists)
  • Before container start
  • Manual trigger via API

​
SFTP Access

Wings includes a built-in SFTP server that provides secure file access.

​
SFTP Authentication

Authentication is validated against the Panel: 
type SftpAuthRequest struct {
    User          string `json:"username"`
    Pass          string `json:"password"`
    IP            string `json:"ip"`
    SessionID     []byte `json:"session_id"`
}

type SftpAuthResponse struct {
    Server      string   `json:"server"`
    Permissions []string `json:"permissions"`
}
Authentication Flow:
  1. User connects to SFTP server
  2. Wings receives credentials
  3. Wings sends ValidateSftpCredentials request to Panel
  4. Panel validates and returns server UUID + permissions
  5. Wings creates SFTP session scoped to that server’s filesystem

​
SFTP Configuration

sftp:
  bind_address: 0.0.0.0
  bind_port: 2022
  read_only: false

​
File Access Scope

SFTP sessions are jailed to the server’s directory: 
User logs in as: admin.{server-uuid}
Root directory: /var/lib/pterodactyl/volumes/{server-uuid}/
User sees: /
Actual path: /var/lib/pterodactyl/volumes/{server-uuid}/
Users cannot access files outside their server’s directory.

​
Read-Only Mode

When read_only: true, all write operations are blocked: 
if config.Get().Sftp.ReadOnly {
    return errors.New("SFTP server is in read-only mode")
}

​
Safety Features

​
Path Traversal Prevention

The UnixFS implementation prevents path traversal attacks: 
func (fs *UnixFS) SafePath(path string) (dirfd int, name string, closeFd func(), err error) {
    // Validate path doesn't escape
    // Return directory fd + safe name
    // Uses openat2 with RESOLVE_BENEATH when available
}
This ensures operations stay within the server’s directory. The filesystem walker doesn’t follow symlinks: 
// From server/filesystem/filesystem.go:247
if err := fs.unixFS.WalkDirat(dirfd, name, func(...) error {
    // Walk implementation doesn't traverse symlinks
})
This prevents:
  • Symlink timing attacks
  • Accessing files outside the server directory
  • Quota bypass via symlinks

​
Denylist Enforcement

Egg configurations can define files that cannot be modified: 
fs.denylist = ignore.CompileIgnoreLines(denylist...)
Operations check against the denylist before proceeding.

​
Read-Only Root Filesystem

Docker containers have read-only root filesystems (environment/docker/container.go:253): 
ReadonlyRootfs: true,
Only the mounted server directory and /tmp are writable.

​
File Operations via API

The HTTP API exposes file operations: Endpoints (from router/router.go:88-104): 
files.GET("/contents", getServerFileContents)
files.GET("/list-directory", getServerListDirectory)
files.PUT("/rename", putServerRenameFiles)
files.POST("/copy", postServerCopyFile)
files.POST("/write", postServerWriteFile)
files.POST("/create-directory", postServerCreateDirectory)
files.POST("/delete", postServerDeleteFiles)
files.POST("/compress", postServerCompressFiles)
files.POST("/decompress", postServerDecompressFiles)
files.POST("/chmod", postServerChmodFile)

​
Compression Operations

Wings supports creating and extracting archives:
  • Supported formats: .tar.gz, .tar, .zip
  • Compression: Creates archives from files/directories
  • Decompression: Extracts archives to specified location

​
Remote Downloads

When enabled, servers can download files from remote URLs: 
files.GET("/pull", middleware.RemoteDownloadEnabled(), getServerPullingFiles)
files.POST("/pull", middleware.RemoteDownloadEnabled(), postServerPullRemoteFile)
files.DELETE("/pull/:download", middleware.RemoteDownloadEnabled(), deleteServerPullRemoteFile)
This is disabled by default for security (config.Api.DisableRemoteDownload).

​
Performance Considerations

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Disk Usage Calculation

Full disk scans are expensive. Wings optimizes by:
  1. Tracking usage in-memory - Atomic updates on operations
  2. Periodic recalculation - Only when needed
  3. Single concurrent scan - lookupInProgress prevents multiple scans

​
Efficient Walking

The directory walker is optimized: 
// From server/filesystem/filesystem.go:247
fs.unixFS.WalkDirat(dirfd, name, func(dirfd int, name, _ string, info ufs.DirEntry, err error) error {
    // Direct syscalls via dirfd
    // No symlink traversal
    // Reused internal buffer
})
This is significantly faster than traditional filepath.Walk.

​
Mimetype Detection

Mimetypes are detected from file content, not extensions: 
m, err = mimetype.DetectReader(f)
This provides accurate types but requires reading file headers.

​
Next Steps

Architecture

Understand the overall system architecture

Server Lifecycle

Learn about server states and transitions

Docker Integration

Understand how Wings uses Docker

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