banger/docs/advanced.md
Thales Maciel 700a1e6e60
cleanup: drop pre-v0.1 migration scaffolding + legacy-behavior refs
banger hasn't shipped a public release — every "legacy", "pre-opt-in",
"previously", "migration note", "no longer" reference in the tree is
pinning against a state no real user's install has ever been in.
That scaffolding has weight: it's a coordinate system future readers
have to decode, and it keeps dead code alive.

Removed (code):
- internal/daemon/ssh_client_config.go
    - vmSSHConfigIncludeBegin / vmSSHConfigIncludeEnd constants and
      every `removeManagedBlock(existing, vm...)` call they enabled
      (legacy inline `Host *.vm` block scrub)
    - cleanupLegacySSHConfigDir (+ its caller in syncVMSSHClientConfig)
      — wiped a pre-opt-in sibling file under $ConfigDir/ssh
    - sameDirOrParent + resolvePathForComparison — only ever used
      by cleanupLegacySSHConfigDir
    - the "also check legacy marker" fallback in
      UserSSHIncludeInstalled / UninstallUserSSHInclude
- internal/store/migrations.go
    - migrateDropDeadImageColumns (migration 2) + its slice entry
    - dropColumnIfExists (orphaned after the above)
    - addColumnIfMissing + the whole "columns added across the pre-
      versioning lifetime" block at the end of migrateBaseline —
      subsumed into the baseline CREATE TABLE
    - `packages_path TEXT` column on the images table (the
      throwaway migration 2 dropped it, but there was never any
      reader)
- internal/daemon/vm.go
    - vmDNSRecordName local wrapper — was justified as "avoid
      pulling vmdns into every file"; three of four callers already
      imported vmdns directly, so inline the one stray call
- internal/cli/cli_test.go
    - TestLegacyRemovedCommandIsRejected (`tui` subcommand never
      shipped)

Removed / simplified (tests):
- ssh_client_config_test.go: dropped TestSameDirOrParentHandlesSymlinks,
  TestSyncVMSSHClientConfigPreservesUserKeyInLegacyDir,
  TestSyncVMSSHClientConfigNarrowsCleanupToLegacyFile,
  TestSyncVMSSHClientConfigLeavesUnexpectedLegacyContents,
  TestInstallUserSSHIncludeMigratesLegacyInlineBlock, plus the
  "legacy posture" regression strings in the remaining happy-path
  test; TestUninstallUserSSHIncludeRemovesBothMarkerBlocks collapsed
  to a single-block test
- migrations_test.go: dropped TestMigrateDropDeadImageColumns_AcrossInstallPaths,
  TestDropColumnIfExistsIsIdempotent; TestOpenReadOnlyDoesNotRunMigrations
  simplified to test against the baseline marker

Removed (docs):
- README.md "**Migration note.**" blockquote about the SSH-key path move
- docs/advanced.md parenthetical "(the old behaviour)"

Reworded (comments):
- Dropped "Previously this file also contained LogLevel DEBUG3..."
  history from vm_disk.go's sshdGuestConfig doc
- Dropped "Call sites that previously read vm.Runtime.{PID,...}"
  from vm_handles.go; now documents the current contract
- Dropped "Pre-v0.1 the defaults are" scaffolding in doctor_test.go
- Dropped "no longer does its own git inspection" phrasing in vm_run.go
- Dropped the "(also cleans up legacy inline block from pre-opt-in
  builds)" aside on the `ssh-config` CLI docstring
- Renamed test var `legacyKey` → `existingKey` in vm_test.go; its
  purpose was "pre-existing authorized_keys line," not banger-legacy

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-04-23 13:56:32 -03:00

3.1 KiB

Advanced flows

banger vm run covers the common sandbox case. This doc is for the rest: scripting, arbitrary images, custom rootfs stacks, long-lived guest processes.

vm create — the low-level primitive

Use when you want to provision without starting, or when you need to script VM creation piecewise.

banger vm create --image debian-bookworm --name testbox --no-start
banger vm start testbox
banger vm ssh testbox
banger vm stop testbox
banger vm delete testbox

Sweep every non-running VM (stopped, created, error) with:

banger vm prune          # interactive confirmation
banger vm prune -f       # skip the prompt

vm create is synchronous by default, but on a TTY it shows live progress until the VM is fully ready.

image pull <oci-ref> — arbitrary container images

For images outside banger's catalog, pull from any OCI registry:

banger image pull docker.io/library/alpine:3.20 --kernel-ref generic-6.12

Layers are flattened, ownership is fixed (setuid binaries, root-owned config preserved), banger's guest agents are injected, and a first-boot systemd service installs openssh-server via the guest's package manager so the VM is reachable on first boot.

See docs/oci-import.md for supported distros, caveats, and the internal/imagepull design.

image register — existing host-side stack

If you already have an ext4 rootfs, a kernel, optional initrd, and optional modules as files on disk:

banger image register --name base \
  --rootfs /abs/path/rootfs.ext4 \
  --kernel-ref generic-6.12

You can mix --kernel-ref (a cataloged kernel) with --rootfs from disk, or pass --kernel /abs/path/vmlinux for a one-off kernel.

For reproducible custom images, write a Dockerfile and publish it to an image catalog. See docs/image-catalog.md.

Workspace primitive

vm run ./repo (see README) handles the common case. For a manual flow against an already-running VM, vm workspace prepare materialises a local git checkout into the guest:

banger vm workspace prepare <vm> ./other-repo --guest-path /root/repo

Default guest path is /root/repo; default mode is a shallow metadata copy plus a tracked-files overlay. Untracked files are skipped by default — pass --include-untracked to ship untracked non-ignored files too. Pass --dry-run to list the exact file set without touching the guest. For repositories with submodules, pass --mode full_copy.

Inspecting boot failures

When a VM's create flow errors ("ssh did not come up within 90s" or similar), the VM is kept alive for inspection:

  • banger vm logs <name> — the firecracker serial console output, the best window into a stuck boot (systemd unit failures, kernel panics, missing modules).
  • banger vm ports <name> — what's listening in the guest. Works as long as banger's vsock agent has come up, even if SSH is wedged.
  • banger vm show <name> — daemon-side state (IP, PID, overlay paths).

--rm on vm run intentionally does NOT fire when the initial ssh wait times out, so the VM stays around for post-mortem.