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package main
import (
"log"
"os"
"os/exec"
"strings"
"syscall"
)
// run the given command, connecting std{in,err,out} with the OS one.
func run(args ...string) error {
cmd := exec.Command(args[0], args[1:]...)
cmd.Stdin = os.Stdin
cmd.Stderr = os.Stderr
cmd.Stdout = os.Stdout
return cmd.Run()
}
// parse the cmdline, return a map[string]string.
func parseCmdline(cmdline string) map[string]string {
line := strings.TrimSuffix(cmdline, "\n")
fields := strings.Fields(line)
out := make(map[string]string, 0)
for _, arg := range fields {
kv := strings.SplitN(arg, "=", 2)
switch len(kv) {
case 1:
out[kv[0]] = ""
case 2:
out[kv[0]] = kv[1]
}
}
return out
}
func main() {
log.Println("Running tvix-init…")
log.Println("Creating /nix/store")
os.MkdirAll("/nix/store", os.ModePerm)
cmdline, err := os.ReadFile("/proc/cmdline")
if err != nil {
log.Printf("Failed to read cmdline: %s\n", err)
}
cmdlineFields := parseCmdline(string(cmdline))
log.Println("Mounting…")
if err := run("mount", "-t", "virtiofs", "tvix", "/nix/store", "-o", "ro"); err != nil {
log.Printf("Failed to run mount: %v\n", err)
}
// If tvix.find is set, invoke find /nix/store
if _, ok := cmdlineFields["tvix.find"]; ok {
log.Println("Listing…")
if err := run("find", "/nix/store"); err != nil {
log.Printf("Failed to run find command: %s\n", err)
}
}
// If tvix.shell is set, invoke the elvish shell
if v, ok := cmdlineFields["tvix.shell"]; ok {
log.Printf("Invoking shell%s\n…", v)
if err := run("elvish"); err != nil {
log.Printf("Failed to run shell: %s\n", err)
}
}
// If tvix.exec is set, invoke the binary specified
if v, ok := cmdlineFields["tvix.exec"]; ok {
log.Printf("Invoking %s\n…", v)
if err := syscall.Exec(v, []string{v}, []string{}); err != nil {
log.Printf("Failed to exec: %s\n", err)
}
}
log.Println("Powering off")
if err := run("poweroff"); err != nil {
log.Printf("Failed to run command: %v\n", err)
}
}
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