Tuto 4 ready

tutorial/4/setns-samples.md

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+#### Exemple C\
+
+Voici un exemple de code C utilisant `setns(2)` :
+
+<div lang="en-US">
+```c
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <sched.h>
+#include <stdlib.h>
+
+// ./a.out /proc/PID/ns/FILE cmd args...
+
+int
+main(int argc, char *argv[])
+{
+    int fd = open(argv[1], O_RDONLY);
+    if (fd == -1)
+    {
+      perror("open");
+      return EXIT_FAILURE;
+    }
+
+    if (setns(fd, 0) == -1)
+    {
+      perror("setns");
+      return EXIT_FAILURE;
+    }
+
+    execvp(argv[2], &argv[2]);
+
+    perror("execve");
+    return EXIT_FAILURE;
+}
+```
+</div>
+
+
+#### Exemple shell\
+
+Dans un shell, on utilisera la commande `nsenter(1)` :
+
+<div lang="en-US">
+```bash
+42sh# unshare --uts /bin/bash
+  inutsns# echo $$
+  42
+  inutsns# hostname jument
+  # Keep this sheel active to perform nexts steps, in another shell.
+
+42sh# hostname
+chaton
+42sh# nsenter --uts=/proc/42/ns/uts /bin/bash
+  inutsns# hostname
+  jument
+```
+</div>