initrd/boot-v1.go

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package main
import (
"fmt"
"log"
"os"
"path/filepath"
"strings"
"syscall"
"time"
yaml "gopkg.in/yaml.v2"
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"novit.tech/direktil/pkg/sysfs"
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)
var loopOffset = 0
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func bootV1() {
log.Print("-- boot v1 --")
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// find and mount /boot
bootMatch := param("boot", "")
bootMounted := false
if bootMatch != "" {
bootFS := param("boot.fs", "vfat")
for i := 0; ; i++ {
devNames := sysfs.DeviceByProperty("block", bootMatch)
if len(devNames) == 0 {
if i > 30 {
fatal("boot partition not found after 30s")
}
log.Print("boot partition not found, retrying")
time.Sleep(1 * time.Second)
continue
}
devFile := filepath.Join("/dev", devNames[0])
log.Print("boot partition found: ", devFile)
mount(devFile, "/boot", bootFS, bootMountFlags, "")
bootMounted = true
break
}
} else {
log.Print("Assuming /boot is already populated.")
}
// load config
cfgPath := param("config", "/boot/config.yaml")
layersDir = filepath.Join("/boot", bootVersion, "layers")
applyConfig(cfgPath, bootMounted)
finalizeBoot()
}
func applyConfig(cfgPath string, bootMounted bool) (cfg *configV1) {
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cfgBytes, err := os.ReadFile(cfgPath)
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if err != nil {
fatalf("failed to read %s: %v", cfgPath, err)
}
cfg = &configV1{}
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if err := yaml.Unmarshal(cfgBytes, cfg); err != nil {
fatal("failed to load config: ", err)
}
// mount layers
if len(cfg.Layers) == 0 {
fatal("no layers configured!")
}
log.Printf("wanted layers: %q", cfg.Layers)
layersInMemory := paramBool("layers-in-mem", false)
const layersInMemDir = "/layers-in-mem"
if layersInMemory {
mkdir(layersInMemDir, 0700)
mount("layers-mem", layersInMemDir, "tmpfs", 0, "")
}
lowers := make([]string, len(cfg.Layers))
for i, layer := range cfg.Layers {
path := layerPath(layer)
info, err := os.Stat(path)
if err != nil {
fatal(err)
}
log.Printf("layer %s found (%d bytes)", layer, info.Size())
if layersInMemory {
log.Print(" copying to memory...")
targetPath := filepath.Join(layersInMemDir, layer)
cp(path, targetPath)
path = targetPath
}
dir := "/layers/" + layer
lowers[i] = dir
loopDev := fmt.Sprintf("/dev/loop%d", i+loopOffset)
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losetup(loopDev, path)
mount(loopDev, dir, "squashfs", layerMountFlags, "")
}
// prepare system root
mount("mem", "/changes", "tmpfs", 0, "")
mkdir("/changes/workdir", 0755)
mkdir("/changes/upperdir", 0755)
mount("overlay", "/system", "overlay", rootMountFlags,
"lowerdir="+strings.Join(lowers, ":")+",upperdir=/changes/upperdir,workdir=/changes/workdir")
if bootMounted {
if layersInMemory {
if err := syscall.Unmount("/boot", 0); err != nil {
log.Print("WARNING: failed to unmount /boot: ", err)
time.Sleep(2 * time.Second)
}
} else {
mount("/boot", "/system/boot", "", syscall.MS_BIND, "")
}
}
// - write configuration
log.Print("writing /config.yaml")
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if err := os.WriteFile("/system/config.yaml", cfgBytes, 0600); err != nil {
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fatal("failed: ", err)
}
// - write files
for _, fileDef := range cfg.Files {
log.Print("writing ", fileDef.Path)
filePath := filepath.Join("/system", fileDef.Path)
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if err := os.MkdirAll(filepath.Dir(filePath), 0755); err != nil {
log.Printf("failed to create dir %s: %v", filepath.Dir(fileDef.Path), err)
}
err = os.WriteFile(filePath, []byte(fileDef.Content), fileDef.Mode)
if err != nil {
fatalf("failed to write %s: %v", fileDef.Path, err)
}
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}
return
}
func finalizeBoot() {
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// clean zombies
cleanZombies()
// switch root
log.Print("switching root")
err := syscall.Exec("/sbin/switch_root", []string{"switch_root",
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"-c", "/dev/console", "/system", "/sbin/init"}, os.Environ())
fatal("switch_root failed: ", err)
}