Alpine template builds fail: glibc busybox in SyncChangesToDisk + missing /usr/bin/ionice and /usr/bin/nice #3597

Summary

Alpine-based template builds fail at the base layer with two distinct exit status 127 errors.

Bug 1 — SyncChangesToDisk uses glibc-linked busybox

File: packages/orchestrator/pkg/template/build/sandboxtools/command.go

SyncChangesToDisk invokes rootfs.SandboxBusyBoxPath + " sync", which resolves to /usr/bin/busybox sync. The /usr/bin/busybox binary is compiled against glibc and cannot be executed on Alpine (musl libc) — it fails with exit status 127.

Bug 2 — /usr/bin/ionice and /usr/bin/nice missing on Alpine

File: packages/orchestrator/pkg/template/build/phases/base/distro/init.go (InitOpenRC)

envd's OOM wrapper hard-codes /usr/bin/ionice and /usr/bin/nice (handler.go):

exec /usr/bin/ionice -c 2 -n 4 /usr/bin/nice -n N ...

On Alpine, util-linux-misc installs ionice to /bin/ionice (not /usr/bin/ionice), and nice lives only at /bin/nice (busybox symlink). Verified:

$ docker run --rm alpine:3.22 sh -c 'apk add --no-cache util-linux-misc >/dev/null 2>&1; ls /usr/bin/ionice /usr/bin/nice 2>&1'
ls: /usr/bin/ionice: No such file or directory
ls: /usr/bin/nice: No such file or directory

Without symlinks at /usr/bin/ionice and /usr/bin/nice, every command envd spawns during the build step layer exits 127.

Fix

See linked PR: add /usr/bin/{ionice,nice} symlinks in the Alpine InitOpenRC provisioning step, and replace the glibc busybox path in SyncChangesToDisk with plain sync + explicit PATH.