issue 1841/S16: kernel_boot answers the loader, entries, kernels, booted entry and the fallback
ADR 0508 §9: the operator sees whether every boot menu lists the fallback kernel, and the room left on /boot.
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@@ -0,0 +1,89 @@
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package main
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// kernel_boot: which loader booted the machine, its entries, the kernels in /boot, the entry it booted and
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// whether the fallback kernel is on the menu (novox/hq ADR 0508 §9, issue 1841). Reads only.
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import (
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"os"
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"path/filepath"
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"regexp"
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"sort"
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"strings"
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"syscall"
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"unicode/utf16"
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)
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const loaderSelected = "sys/firmware/efi/efivars/LoaderEntrySelected-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f"
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// BootState is what kernel_boot answers.
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type BootState struct {
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Loader string `json:"loader"`
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Entries []string `json:"entries"`
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Kernels []string `json:"kernels"`
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Booted string `json:"booted"`
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FallbackPresent bool `json:"fallback_present"`
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BootFreeKiB int64 `json:"boot_free_kib"`
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}
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var grubKernel = regexp.MustCompile(`(?m)^\s*linux\s+(?:/boot)?/(vmlinuz-\S+)`)
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var grubTitle = regexp.MustCompile(`(?m)^\s*menuentry\s+'([^']*)'`)
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var bootImage = regexp.MustCompile(`BOOT_IMAGE=(?:/boot)?/?(\S+)`)
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// Boot reads the machine, the loader the way the boot-entries script does: the loader's EFI variable means
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// systemd-boot, a grub.cfg without it GRUB.
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func (m *Machine) Boot() (*BootState, error) {
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b := &BootState{Loader: "none", Entries: []string{}, Kernels: []string{}}
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files, _ := filepath.Glob(m.path("boot/vmlinuz-*"))
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for _, f := range files {
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b.Kernels = append(b.Kernels, filepath.Base(f))
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}
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sort.Strings(b.Kernels)
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hasKernel := func(name string) bool {
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for _, k := range b.Kernels {
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if k == name {
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return true
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}
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}
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return false
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}
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var s syscall.Statfs_t
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if err := syscall.Statfs(m.path("boot"), &s); err == nil {
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b.BootFreeKiB = int64(s.Bavail) * int64(s.Bsize) / 1024
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}
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if raw, err := os.ReadFile(m.path(loaderSelected)); err == nil {
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b.Loader = "systemd-boot"
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if len(raw) > 4 {
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var u []uint16
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for i := 4; i+1 < len(raw); i += 2 {
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u = append(u, uint16(raw[i])|uint16(raw[i+1])<<8)
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}
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b.Booted = strings.TrimRight(string(utf16.Decode(u)), "\x00")
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}
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files, _ := filepath.Glob(m.path("boot/loader/entries/*.conf"))
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for _, f := range files {
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b.Entries = append(b.Entries, filepath.Base(f))
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}
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sort.Strings(b.Entries)
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if raw, err := os.ReadFile(m.path("boot/loader/entries/mesh-linux-lts.conf")); err == nil {
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b.FallbackPresent = strings.Contains(string(raw), "/vmlinuz-linux-lts") && hasKernel("vmlinuz-linux-lts")
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}
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return b, nil
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}
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if raw, err := os.ReadFile(m.path("boot/grub/grub.cfg")); err == nil {
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b.Loader = "grub"
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for _, t := range grubTitle.FindAllStringSubmatch(string(raw), -1) {
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b.Entries = append(b.Entries, t[1])
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}
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for _, k := range grubKernel.FindAllStringSubmatch(string(raw), -1) {
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if k[1] == "vmlinuz-linux-lts" && hasKernel("vmlinuz-linux-lts") {
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b.FallbackPresent = true
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}
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}
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if cmd, err := m.read("proc/cmdline"); err == nil {
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if i := bootImage.FindStringSubmatch(cmd); i != nil {
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b.Booted = i[1]
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}
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}
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}
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return b, nil
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}
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@@ -0,0 +1,90 @@
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package main
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// kernel_boot over stand-in roots: a systemd-boot machine with and without the fallback entry, a GRUB machine
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// with and without the fallback kernel in its menu, and a machine with neither (novox/hq ADR 0508 §9, issue 1841).
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import (
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"os"
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"path/filepath"
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"testing"
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)
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const selectedVar = "sys/firmware/efi/efivars/LoaderEntrySelected-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f"
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func put(t *testing.T, root, p, content string) {
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t.Helper()
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full := filepath.Join(root, p)
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if err := os.MkdirAll(filepath.Dir(full), 0o755); err != nil {
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t.Fatal(err)
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}
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write(t, full, content, 0o644)
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}
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func bootOf(t *testing.T, root string) *BootState {
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t.Helper()
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got, err := (&Machine{Root: root}).Boot()
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if err != nil {
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t.Fatal(err)
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}
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return got
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}
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func TestKernelBootReadsASystemdBootMachineWithItsFallbackEntry(t *testing.T) {
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root := t.TempDir()
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put(t, root, selectedVar, "\x07\x00\x00\x00a\x00r\x00c\x00h\x00.\x00c\x00o\x00n\x00f\x00\x00\x00")
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put(t, root, "boot/loader/entries/arch.conf", defaultEntry)
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put(t, root, "boot/loader/entries/mesh-linux-lts.conf", "title Arch Linux (linux-lts, fallback)\nlinux /vmlinuz-linux-lts\n")
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put(t, root, "boot/vmlinuz-linux", "k")
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put(t, root, "boot/vmlinuz-linux-lts", "k")
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got := bootOf(t, root)
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if got.Loader != "systemd-boot" || got.Booted != "arch.conf" || !got.FallbackPresent {
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t.Fatalf("%+v", got)
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}
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if len(got.Entries) != 2 || got.Entries[0] != "arch.conf" || got.Entries[1] != "mesh-linux-lts.conf" {
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t.Fatalf("entries: %v", got.Entries)
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}
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if len(got.Kernels) != 2 || got.Kernels[0] != "vmlinuz-linux" || got.Kernels[1] != "vmlinuz-linux-lts" {
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t.Fatalf("kernels: %v", got.Kernels)
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}
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if got.BootFreeKiB <= 0 {
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t.Fatalf("free: %d", got.BootFreeKiB)
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}
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}
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func TestKernelBootSaysASystemdBootMachineHasNoFallbackYet(t *testing.T) {
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root := t.TempDir()
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put(t, root, selectedVar, "\x07\x00\x00\x00a\x00r\x00c\x00h\x00.\x00c\x00o\x00n\x00f\x00\x00\x00")
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put(t, root, "boot/loader/entries/arch.conf", defaultEntry)
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put(t, root, "boot/vmlinuz-linux", "k")
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// The entry file alone is not the fallback: the kernel it names must be in /boot.
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put(t, root, "boot/loader/entries/mesh-linux-lts.conf", "linux /vmlinuz-linux-lts\n")
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if got := bootOf(t, root); got.FallbackPresent {
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t.Fatalf("a fallback entry without its kernel: %+v", got)
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}
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}
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func TestKernelBootReadsAGrubMachine(t *testing.T) {
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root := t.TempDir()
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put(t, root, "boot/grub/grub.cfg", grubMenu)
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put(t, root, "boot/vmlinuz-linux", "k")
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put(t, root, "proc/cmdline", bootedCmdline)
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got := bootOf(t, root)
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if got.Loader != "grub" || got.FallbackPresent || got.Booted != "vmlinuz-linux" {
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t.Fatalf("%+v", got)
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}
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if len(got.Entries) != 2 || got.Entries[0] != "Arch Linux" {
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t.Fatalf("entries: %v", got.Entries)
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}
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put(t, root, "boot/vmlinuz-linux-lts", "k")
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put(t, root, "boot/grub/grub.cfg", grubMenu+"menuentry 'Arch Linux LTS' {\n\tlinux\t/boot/vmlinuz-linux-lts root=x rw\n}\n")
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if got := bootOf(t, root); !got.FallbackPresent {
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t.Fatalf("%+v", got)
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}
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}
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func TestKernelBootSaysWhenThereIsNoLoader(t *testing.T) {
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got := bootOf(t, t.TempDir())
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if got.Loader != "none" || got.FallbackPresent || len(got.Entries) != 0 {
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t.Fatalf("%+v", got)
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}
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}
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@@ -46,5 +46,15 @@ func tools(m *Machine) []stdio.Tool {
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return m.HugePages(n)
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},
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},
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{
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Name: "kernel_boot",
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Description: "How this machine boots and whether the fallback kernel is on its menu (novox/hq ADR 0508 §9): the loader that booted it " +
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"(systemd-boot, read from the EFI variable it sets, grub, or none), the menu's entries, the kernels in /boot, the entry " +
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"the machine booted (systemd-boot) or the kernel image it booted (grub), whether the fallback kernel linux-lts is on " +
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"the menu with its kernel in /boot, and the room free on /boot in KiB (the fallback kernel needs about 72 MB). " +
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"Replaces ls /boot, bootctl list, reading grub.cfg and df /boot. (r)",
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Input: schema(map[string]any{}),
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Run: func(args map[string]any) (any, error) { return m.Boot() },
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},
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}
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}
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