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fix: host-side permission fix + SKIP_INIT volume persistence docs

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Replace the container-side _fix_permissions for vendor NOS containers with a
host-side pass that walks the node's project directories directly (they are
the Docker bind-mount sources): records mode:uid:gid into .gns3_perms and
chowns to the GNS3 user. No docker exec, no container restart — the base
implementation restarts an exited container just to chown, and after the
restart the mount --bind bridge is gone so it would fix the overlay copy
instead of the host files.

The pass runs at start (after _setup_skip_init_volumes seeds and bridges the
volumes) so the controller can read project files while the node runs, and
again at stop for files written during runtime.

Update docker-exec-console.md: VendorDockerVM architecture, hook points,
class-selection factory, volume-persistence lifecycle, and new
troubleshooting entries.
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YueGuobin 2026-08-12 22:58:46 +08:00
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154
docs/features/docker-exec-console.md
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@ -43,12 +43,47 @@ they stay host-side configuration.
| `GNS3_INTERFACE_NAMES=mgmt0,e1-1,e1-2,e1-3` | Rename the injected interfaces in adapter order instead of the default `eth{N}`. SR Linux expects `mgmt0` + `e1-N`; without this it does not recognise its datapath. |
| `GNS3_CONSOLE_CMD=/opt/srlinux/bin/sr_cli` | Command run by the `docker_exec` console inside the container. |
## Architecture: `VendorDockerVM` subclass
All vendor-specific logic lives in a `VendorDockerVM(DockerVM)` subclass in
`gns3server/compute/docker/vendor_docker_vm.py` — `docker_vm.py` itself stays
on its baseline behaviour and is never touched by this feature.
`DockerVM` exposes four small extension hooks (pure refactorings, zero
behaviour change for existing nodes):
| Hook | Baseline behaviour | `VendorDockerVM` override |
|------|--------------------|---------------------------|
| `_prepare_init_and_interface_env(params)` | prepend `/gns3/init.sh`, set `GNS3_MAX_ETHERNET=eth{N-1}` | conditional init.sh (`GNS3_SKIP_INIT`), `GNS3_MAX_ETHERNET` follows the interface rename |
| `_start_console_server()` | telnet/ssh/http console dispatch | adds the `docker_exec` branch |
| `_get_container_ifname(adapter_number)` | `eth{N}` | `GNS3_INTERFACE_NAMES` lookup, fallback `eth{N}` |
| `_cleanup_console_resources()` | no-op | closes the docker-exec pty socket before restart/stop |
### Class selection
The Docker manager picks the class per node in `Docker.create_node()`
(`gns3server/compute/docker/__init__.py`):
```python
def _select_node_class(self, **kwargs):
if kwargs.get("console_type") == "docker_exec":
return VendorDockerVM
return DockerVM
```
`console_type == "docker_exec"` is the **only** trigger — every other console
type (telnet, vnc, ssh, http, …) keeps using the unmodified `DockerVM`. All
vendor features are opt-in: without the `GNS3_*` environment variables a
`VendorDockerVM` instance behaves identically to `DockerVM` (init.sh still
runs, interfaces stay `eth{N}`, the exec command defaults to `/bin/sh`), so a
regular container can use `docker_exec` too.
## The `docker_exec` console type
Setting `console_type: "docker_exec"` makes the node's primary console port run
`_start_docker_exec_console()` instead of the attach-to-PID-1 path.
### Architecture
### Console architecture
```mermaid
graph LR
@ -67,7 +102,8 @@ behaves.
### Implementation
**File**: `gns3server/compute/docker/docker_vm.py` — `_start_docker_exec_console()`
**File**: `gns3server/compute/docker/vendor_docker_vm.py` —
`_start_docker_exec_console()`
A small subclass `_LazyExecTelnetServer(AsyncioTelnetServer)` implements the
console. Key points:
@ -88,7 +124,13 @@ console. Key points:
CLI"* otherwise), and `Env: ["TERM=xterm"]` (the TUI library needs a
recognised terminal).
3. **Hijacked raw-HTTP start.** The exec is started with
3. **while-true wrapper.** The command is wrapped in
`sh -c "while true; do <cmd>; done"` so that when the CLI exits (user types
`quit`, or the NOS's own idle timeout logs the session out), a fresh CLI
instance starts in the same pty instead of killing the shared console
session.
4. **Hijacked raw-HTTP start.** The exec is started with
`POST exec/{eid}/start` sent as a raw HTTP upgrade over the Docker unix
socket (`asyncio.open_unix_connection`), the same approach docker-py uses.
This is required because aiohttp's websocket client (`ws_connect`) is
@ -96,11 +138,11 @@ console. Key points:
upgrade succeeds (101). With `Tty:true` the response body is a raw,
non-multiplexed bidirectional pty byte stream — no frame demux needed.
4. **NAWS → exec resize.** The telnet server runs with `naws=True`; the
5. **NAWS → exec resize.** The telnet server runs with `naws=True`; the
`window_size_changed_callback` calls `POST exec/{eid}/resize?h=&w=` so the
TUI lays out for the xterm.js window size.
5. **Binary passthrough + redraw.** `binary=True` so TUI escape sequences reach
6. **Binary passthrough + redraw.** `binary=True` so TUI escape sequences reach
xterm.js intact; `echo=False` (the pty echoes). On every client (re)connect
a `Ctrl-L` (`\x0c`) is sent to the pty so a TUI that already drew its
screen for a previous client redraws for the new one (otherwise a
@ -147,9 +189,62 @@ The exec-API approach fixes all of these: a real pty (`Tty:true`), a real size
### Persistent state
For SR Linux, persist `/etc/opt/srlinux` (config / AAA users / TLS certs) by
adding it to the node's `extra_volumes`. `/var/opt/srlinux` does **not** exist
on current SR Linux images; `/var/log/srlinux` holds logs (optional).
For SR Linux, persist `/etc/opt/srlinux` (config / AAA users / TLS certs) and
`/var/log/srlinux` (logs, optional) by adding them to the node's
`extra_volumes`. The image also declares its own `VOLUME` directories
(e.g. `/opt/srlinux/appmgr`), which GNS3 persists automatically.
## Volume persistence with `GNS3_SKIP_INIT`
This is the one place where skipping init.sh changes behaviour beyond boot:
`/gns3/init.sh` normally performs the volume-persistence bridge, and without it
**nothing writes through to the host** — the container writes to its overlay
filesystem and the data is lost on stop.
The bridge (see init.sh lines 35–52) has two parts:
```
host ──Docker bind mount──▶ /gns3volumes/etc/opt/srlinux (always mounted)
│ init.sh: mount --bind
▼
/etc/opt/srlinux (where the NOS writes)
```
`VendorDockerVM` replicates this for SKIP_INIT containers:
1. **`_setup_skip_init_volumes()`** — runs once per start, right after the
container is up (`VendorDockerVM.start()`). For each persistent volume it
`docker exec`s a busybox script that:
- seeds the host directory with the container's original files on first
start (`cp -a` + `.gns3_perms` marker), exactly like init.sh;
- `mount --bind /gns3volumes<path> <path>` to bridge persistent storage
back to the in-container path — on subsequent starts the persisted data
replaces the fresh overlay content;
- restores the permissions recorded in `.gns3_perms` at the previous stop
(best-effort).
2. **Host-side `_fix_permissions()` override** — `DockerVM._fix_permissions`
is container-side (busybox via `docker exec`) and restarts an exited
container just to chown; after a restart the `mount --bind` bridge is gone,
so it would fix the overlay copy and not the host files. The override
instead walks the host-side directories under the node's project directory
directly (they *are* the Docker bind-mount sources), records
`mode:uid:gid:path` into `.gns3_perms` and chowns to the GNS3 user —
no running container required, no restart. It runs both at start (so the
controller can read project files while the node runs) and at stop.
> Rootful-Docker assumption: the `.gns3_perms` uid/gid values are recorded from
> the host's view. With rootful Docker (no userns remap) in-container and host
> ids coincide, so restore semantics are identical to init.sh's. This would
> need revisiting for userns-remapped daemons.
### Lifecycle summary
| Phase | Normal Docker node | `VendorDockerVM` + `GNS3_SKIP_INIT` |
|-------|--------------------|--------------------------------------|
| start | init.sh seeds + bind-mounts + restores perms (in-container, before the app starts) | `docker exec` after start: seed + bind-mount + restore perms; then host-side chown |
| stop | container-side `_fix_permissions` (restarts an exited container) | host-side `_fix_permissions` (no container needed) |
| volume config | identical `_mount_binds` (host → `/gns3volumes<path>`) | identical |
## Troubleshooting
@ -180,23 +275,51 @@ on current SR Linux images; `/var/log/srlinux` holds logs (optional).
network-instance before ping works. This is SR Linux behaviour, not a GNS3
issue.
**7. "Session has been idle, will logout in 300 seconds" → Connection closed**
- SR Linux's own CLI idle timeout. The while-true wrapper restarts the CLI
automatically, but to keep a permanent session disable the timeout in the
CLI: `enter candidate` → `/system cli idle-timeout disable` → `commit now`.
**8. Controller logs `Permission denied` reading files under the node's
project directory while the node runs**
- Root-written files inside a persistent volume. The host-side
`_fix_permissions` pass runs at start (fixes the seeded files) and at stop;
files created by the container *during* runtime become readable after the
next stop.
**9. Persistent volume empty on the host after `save` + stop**
- Ensure `GNS3_SKIP_INIT=1` is set (so the host-side bridge path is taken) and
the volume path is in `extra_volumes`; check the compute log for
`Volume '<path>' bound to persistent storage`.
## Limitations
1. **Shared session (broadcast).** All console clients share one CLI session
and can see each other's input — identical to GNS3's existing primary
console model. There is no per-client independent session.
2. **`reset_console` not wired.** The console-reset action only handles
`telnet`/`ssh`; it is a no-op for `docker_exec` (non-blocking; reconnect
works fine).
`telnet`/`ssh`; it is a no-op for `docker_exec` (non-blocking; reconnect
works fine).
3. **Prototype knobs.** `GNS3_SKIP_INIT` / `GNS3_INTERFACE_NAMES` /
`GNS3_CONSOLE_CMD` are environment-driven; they are not yet first-class node
schema fields and are not declared in the appliance (`gns3a`) schema.
`GNS3_CONSOLE_CMD` are environment-driven; they are not yet first-class node
schema fields and are not declared in the appliance (`gns3a`) schema.
4. **Rootful-Docker assumption** for the host-side `.gns3_perms` recording
(see the volume-persistence section).
5. **Post-boot volume bridge.** The bind-mount bridge is established after the
vendor entrypoint has started (init.sh would do it before). A NOS that
strictly requires its persisted files at its very first read may need a
different boot arrangement.
## References
- `gns3server/compute/docker/docker_vm.py` — `_start_docker_exec_console`,
`_LazyExecTelnetServer`, `_add_ubridge_connection` (interface rename),
`create()` (env parsing, skip-init, `GNS3_MAX_ETHERNET`).
- `gns3server/compute/docker/vendor_docker_vm.py` — `VendorDockerVM`:
`_start_docker_exec_console`, `_LazyExecTelnetServer`,
`_setup_skip_init_volumes`, host-side `_fix_permissions`, `start()`.
- `gns3server/compute/docker/docker_vm.py` — `DockerVM` extension hooks
(`_prepare_init_and_interface_env`, `_start_console_server`,
`_get_container_ifname`, `_cleanup_console_resources`).
- `gns3server/compute/docker/__init__.py` — `Docker._select_node_class` /
`create_node` factory.
- `gns3server/compute/base_node.py` — console WebSocket guard.
- `gns3server/schemas/common.py` — `ConsoleType.docker_exec`.
- containerlab `nodes/srl/srl.go` — reference for SR Linux launch command and
@ -206,4 +329,5 @@ on current SR Linux images; `/var/log/srlinux` holds logs (optional).
| Version | Date | Changes |
|---------|------|---------|
| 1.1 | 2026-08-12 | Refactor: vendor logic extracted from `DockerVM` into `VendorDockerVM` subclass with 4 hook points + class-selection factory. Add SKIP_INIT volume persistence (`_setup_skip_init_volumes` + host-side `_fix_permissions`) and lifecycle comparison. Add troubleshooting entries for idle timeout and permission-denied files. |
| 1.0 | 2026-08-12 | Initial documentation of the `docker_exec` console and vendor NOS knobs. |

76
gns3server/compute/docker/vendor_docker_vm.py
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@ -29,6 +29,8 @@ container behaves identically to DockerVM.
import asyncio
import json
import logging
import os
import stat
from gns3server.utils.asyncio.telnet_server import AsyncioTelnetServer
from gns3server.compute.docker.docker_vm import DockerVM
@ -119,6 +121,80 @@ class VendorDockerVM(DockerVM):
await super().start()
if self.status == "started" and not self._gns3_init:
await self._setup_skip_init_volumes()
# Fix host-side ownership of the seeded volume right away so the
# controller can read project files while the node runs. Reset the
# "fixed" flag afterwards: files written by the container during
# runtime still need the stop-time pass.
await self._fix_permissions()
self._permissions_fixed = False
async def _fix_permissions(self):
"""
Host-side override of DockerVM._fix_permissions for SKIP_INIT
containers. The persistent volumes are Docker bind mounts of
directories under the node's project directory, so ownership is fixed
directly on the host — no docker exec, no container restart required
(the base implementation restarts an exited container just to chown,
which is wasteful for vendor NOS images).
Two passes per volume, mirroring the base/busybox behaviour:
1. record each entry's container-visible mode/uid/gid into
`.gns3_perms` (same `mode:uid:gid:path` format init.sh consumes,
paths are in-container absolute so the restore inside the
container resolves them);
2. chmod u+rX + chown to the host user so the GNS3 process can read
and delete files from the project directory.
"""
uid, gid = os.getuid(), os.getgid()
for volume in self._volumes:
path = os.path.join(self.working_dir, os.path.relpath(volume, "/"))
if not os.path.isdir(path):
continue
def onerror(exc):
log.debug("Could not walk '%s' for container '%s': %s", exc.filename, self._name, exc)
# 1. record container-visible permissions for restore at next start
try:
with open(os.path.join(path, ".gns3_perms"), "w") as perms_file:
for root, dirs, files in os.walk(path, onerror=onerror):
for entry in dirs + files:
entry_path = os.path.join(root, entry)
try:
st = os.lstat(entry_path)
except OSError:
continue
container_path = os.path.join(volume, os.path.relpath(entry_path, path))
perms_file.write(
f"{stat.S_IMODE(st.st_mode):o}:{st.st_uid}:{st.st_gid}:{container_path}\n"
)
except OSError as e:
log.warning(
"Could not record permissions for '%s' on container '%s': %s", path, self._name, e
)
continue
# 2. chmod u+rX + chown to the host user
for root, dirs, files in os.walk(path, onerror=onerror):
for entry in dirs + files:
entry_path = os.path.join(root, entry)
try:
st = os.lstat(entry_path)
is_link = stat.S_ISLNK(st.st_mode)
if not is_link:
mode = stat.S_IMODE(st.st_mode)
new_mode = mode | 0o400 # u+r
if stat.S_ISDIR(st.st_mode) or (mode & 0o111): # u+X
new_mode |= 0o100
os.chmod(entry_path, new_mode)
os.lchown(entry_path, uid, gid)
except OSError as e:
log.debug(
"Could not fix permissions on '%s' for container '%s': %s",
entry_path, self._name, e,
)
self._permissions_fixed = True
async def _setup_skip_init_volumes(self):
"""