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daemon: rewrite ensureWorkDisk no-seed path to skip the mount + cp

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The no-seed branch used to mount the base rootfs read-only, mount
the freshly mkfs'd work disk read-write, sudo-cp /root from one to
the other, then flatten any accidental /root/root/ nesting. Five
sudo call sites packed into a fallback that the common image path
doesn't even exercise.

Replace with: `mkfs.ext4 -F -E root_owner=0:0` and nothing else.
mkfs already stamps inode 2 as root:root:0755 — sshd's StrictModes
walks that dir's ownership when the work disk mounts at /root in
the guest, so getting it right from mkfs means authsync can just
write authorized_keys without any repair pass.

Tradeoff: no-seed VMs lose the base rootfs's default /root dotfiles
(.bashrc, .profile). The no-seed path is explicitly the degraded
fallback — `banger doctor` already warns about it — and users who
want those back have two documented knobs: rebuild the image with
a work-seed, or land them via [[file_sync]].

Sudo call sites removed: 5 (MountTempDir × 2, sudo cp -a,
flattenNestedWorkHome's chmod/cp/rm). flattenNestedWorkHome itself
stays alive for now — authsync + image_seed still call it — and
gets deleted in commit 5 once its last caller goes away.

While here: fix the freshly-added EnsureExt4RootPerms helper.
`set_inode_field <2> mode N` overwrites the full i_mode word
instead of preserving the type nibble, so the initial
implementation that passed just the permission bits (0755) would
reset the fs root to regular-file shape and break the next kernel
mount with "Structure needs cleaning." The corrected call OR's in
S_IFDIR (0o040000) explicitly. Test updated to match.

Smoke: 21/21 scenarios green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Thales Maciel 2026-04-23 18:09:32 -03:00
parent 77043966d4
commit 0e28504892
No known key found for this signature in database
GPG key ID: 33112E6833C34679
3 changed files with 37 additions and 53 deletions
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10
internal/system/ext4_test.go
View file

@ -285,9 +285,13 @@ func TestEnsureExt4RootPerms_UsesRootInodeLiteral(t *testing.T) {
t.Fatalf("EnsureExt4RootPerms: %v", err)
}
// Must address inode 2 — the ext4 root directory.
if !strings.Contains(capturedScript, "sif <2> mode 0755") {
t.Fatalf("script missing root-inode mode line:\n%s", capturedScript)
// Must address inode 2 — the ext4 root directory — with the
// FULL i_mode word (S_IFDIR | 0755 = 040755). debugfs's
// set_inode_field doesn't preserve the type nibble, so passing
// just the permission bits (0755) would reset the root inode
// to regular-file shape and break the next kernel mount.
if !strings.Contains(capturedScript, "set_inode_field <2> mode 040755") {
t.Fatalf("script missing root-inode mode line with S_IFDIR+0755:\n%s", capturedScript)
}
if !strings.Contains(capturedScript, "set_inode_field <2> uid 0") {
t.Fatalf("script missing root-inode uid line:\n%s", capturedScript)