198 lines
7.1 KiB
Markdown
198 lines
7.1 KiB
Markdown
# BUGFIX: /dev/sdb not accessible inside container
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## Problem
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`FormatAndMount` fails with `stat /dev/sdb: no such file or directory` because block device nodes
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don't exist inside the container's `/dev`.
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Even with `privileged: true`, Docker creates its own tmpfs at `/dev` with minimal device nodes.
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The explicit `- /dev:/dev` volume mount in docker-compose.yml is silently overridden by Docker's
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internal `/dev` tmpfs setup — `docker inspect` shows no bind mount for `/dev`.
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## Root Cause
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Docker always creates a fresh tmpfs for `/dev` inside containers. The `privileged: true` flag
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relaxes cgroup device access (the kernel allows I/O to any device), but doesn't populate `/dev`
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with all host device nodes. The bind mount `- /dev:/dev` conflicts with Docker's own `/dev`
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management and gets silently dropped.
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## Fix
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Mount host `/dev` at a **different path** inside the container. The device nodes at `/host-dev/sdb`
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are real block devices that the kernel will allow I/O to (because `privileged: true`).
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### 1. docker-compose.yml change
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```yaml
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volumes:
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# ...existing...
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# Block devices — mounted at /host-dev (can't override Docker's /dev)
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- /dev:/host-dev:rw
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```
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Change `- /dev:/dev` to `- /dev:/host-dev:rw`
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### 2. Go code: Add host device path constant
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In `internal/storage/` package (e.g., `format_linux.go` or a new `paths.go`):
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```go
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const (
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// HostDevPath is where the host's /dev is mounted inside the container.
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// Docker overrides /dev with its own tmpfs, so we mount at /host-dev.
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HostDevPath = "/host-dev"
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// HostFstabPath is where the host's /etc/fstab is mounted.
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HostFstabPath = "/host-fstab"
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)
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// HostDevicePath converts a standard device path to the container-accessible path.
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// "/dev/sdb" → "/host-dev/sdb"
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// "/dev/sdb1" → "/host-dev/sdb1"
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func HostDevicePath(devPath string) string {
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if strings.HasPrefix(devPath, "/dev/") {
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return HostDevPath + "/" + strings.TrimPrefix(devPath, "/dev/")
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}
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return devPath
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}
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```
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### 3. Update all device operations to use HostDevicePath()
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In `format_linux.go` (or wherever FormatAndMount is):
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```go
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// Validation — check device exists
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hostDev := HostDevicePath(req.DevicePath) // "/dev/sdb" → "/host-dev/sdb"
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if _, err := os.Stat(hostDev); err != nil {
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return fmt.Errorf("device not found: %s", req.DevicePath)
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}
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// Partition — use host device path
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cmd := exec.Command("sfdisk", hostDev)
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// Format — use host device path
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cmd := exec.Command("mkfs.ext4", "-F", "-L", label, HostDevicePath(partPath))
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// blkid — use host device path
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cmd := exec.Command("blkid", "-o", "value", "-s", "UUID", HostDevicePath(partPath))
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// mount — use host device path for source, real path for target
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cmd := exec.Command("mount", HostDevicePath(partPath), mountPath)
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```
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### 4. Update ScanDisks blkid enrichment
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In `scan_linux.go`, the `enrichWithBlkid` function and `getSystemDiskNames` function
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use `blkid` which scans `/dev` by default. Update to scan `/host-dev`:
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```go
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// enrichWithBlkid — run blkid on /host-dev to get filesystem info
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func enrichWithBlkid(disks []BlockDevice) {
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// blkid by default scans /dev — we need it to scan /host-dev
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// Option 1: Run blkid with explicit device paths from /host-dev
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// Option 2: Run blkid -o export and it will find devices from /proc/partitions
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// blkid -o export still works because it reads /proc/partitions (kernel-level)
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// and then probes the devices. With privileged mode, it can probe via /proc.
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// BUT the DEVNAME in output will say /dev/sdb1, not /host-dev/sdb1.
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// That's fine — we match by device name anyway.
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out, err := exec.Command("blkid", "-o", "export").Output()
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// ... parsing as before, matching by /dev/xxx paths ...
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}
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// For getSystemDiskNames, blkid -U <uuid> returns /dev/xxx paths which is correct
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// for fstab parsing (fstab uses /dev/xxx paths too).
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// No changes needed there — it's just resolving UUIDs to device names.
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```
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**Note:** `blkid -o export` may not find devices if it can only see Docker's minimal `/dev`.
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In that case, enumerate `/host-dev/sd*` explicitly:
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```go
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func enrichWithBlkid(disks []BlockDevice) {
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for i := range disks {
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for j := range disks[i].Partitions {
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p := &disks[i].Partitions[j]
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hostPath := HostDevicePath(p.Path) // "/host-dev/sdb1"
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// Probe individually
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if fstype, err := exec.Command("blkid", "-o", "value", "-s", "TYPE", hostPath).Output(); err == nil {
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p.FSType = strings.TrimSpace(string(fstype))
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}
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if uuid, err := exec.Command("blkid", "-o", "value", "-s", "UUID", hostPath).Output(); err == nil {
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p.UUID = strings.TrimSpace(string(uuid))
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}
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if label, err := exec.Command("blkid", "-o", "value", "-s", "LABEL", hostPath).Output(); err == nil {
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p.Label = strings.TrimSpace(string(label))
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}
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}
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}
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}
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```
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### 5. fstab writing — use real /dev paths
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When writing to fstab, use UUID-based entries (already the plan), so no /dev path needed:
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```
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UUID=<uuid> /mnt/hdd_1 ext4 defaults,nofail,noatime 0 2
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```
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The UUID is obtained from `blkid` using the `/host-dev/sdb1` path, but the UUID itself
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is filesystem-level and doesn't depend on device path.
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### 6. mount command — needs special handling
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`mount /host-dev/sdb1 /mnt/hdd_1` should work because `/host-dev/sdb1` is a real block
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device node (same major:minor as the host's `/dev/sdb1`). The kernel doesn't care about
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the path — it uses the device numbers.
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However, `mount` may also accept UUID directly:
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```go
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exec.Command("mount", "UUID="+uuid, mountPath)
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```
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This is even better — no device path needed at all. But it requires the kernel to find
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the device, which should work since the device is visible in `/proc/partitions`.
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**Recommended:** Use the device path approach (`mount /host-dev/sdb1 /mnt/hdd_1`) as
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it's more explicit and debuggable.
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### 7. Also update docker-setup.sh
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If `docker-setup.sh` generates the controller compose file, update the `/dev` mount:
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```bash
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# Was:
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echo " - /dev:/dev" >> "$compose_file"
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# Now:
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echo " - /dev:/host-dev:rw" >> "$compose_file"
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```
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Check in `docker-setup.sh` whether all necessary packages are deployed during installation (rsync, etc.)
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### 8. Update documentation
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Update CONTEXT.md, CHANGELOG.md, README.md
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## Summary of changes
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| File | Change |
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|------|--------|
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| `controller/docker-compose.yml` | `/dev:/dev` → `/dev:/host-dev:rw` |
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| `controller/internal/storage/format_linux.go` | Use `HostDevicePath()` for all device operations |
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| `controller/internal/storage/scan_linux.go` | Use `HostDevicePath()` for `blkid` probing |
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| `controller/internal/storage/paths.go` (NEW) | `HostDevPath`, `HostFstabPath`, `HostDevicePath()` |
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| `scripts/docker-setup.sh` | Update compose generation |
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## Quick test after fix
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```bash
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# Rebuild + redeploy controller
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# Then verify:
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docker exec felhom-controller ls -la /host-dev/sd*
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# Should show: /host-dev/sda, /host-dev/sda1, sda2, sda3, /host-dev/sdb, /host-dev/sdb1
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# Try format (from UI or manually):
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docker exec felhom-controller blkid /host-dev/sdb1
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# Should work (empty output = no filesystem, which is correct for unformatted)
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``` |