diff --git a/isolate/config.c b/isolate/config.c
new file mode 100644
--- /dev/null
+++ b/isolate/config.c
@@ -0,0 +1,168 @@
+/*
+ *	Process Isolator -- Configuration File
+ *
+ *	(c) 2016 Martin Mares <mj@ucw.cz>
+ */
+
+#include "isolate.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define MAX_LINE_LEN 1024
+
+char *cf_box_root;
+char *cf_cg_root;
+char *cf_cg_parent;
+int cf_first_uid;
+int cf_first_gid;
+int cf_num_boxes;
+
+static int line_number;
+static struct cf_per_box *per_box_configs;
+
+static void NONRET
+cf_err(char *msg)
+{
+  die("Error in config file, line %d: %s", line_number, msg);
+}
+
+static char *
+cf_string(char *val)
+{
+  return xstrdup(val);
+}
+
+static int
+cf_int(char *val)
+{
+  char *end;
+  errno = 0;
+  long int x = strtol(val, &end, 10);
+  if (errno || end == val || end && *end)
+    cf_err("Invalid number");
+  if ((long int)(int) x != x)
+    cf_err("Number out of range");
+  return x;
+}
+
+static void
+cf_entry_toplevel(char *key, char *val)
+{
+  if (!strcmp(key, "box_root"))
+    cf_box_root = cf_string(val);
+  else if (!strcmp(key, "cg_root"))
+    cf_cg_root = cf_string(val);
+  else if (!strcmp(key, "cg_parent"))
+    cf_cg_parent = cf_string(val);
+  else if (!strcmp(key, "first_uid"))
+    cf_first_uid = cf_int(val);
+  else if (!strcmp(key, "first_gid"))
+    cf_first_gid = cf_int(val);
+  else if (!strcmp(key, "num_boxes"))
+    cf_num_boxes = cf_int(val);
+  else
+    cf_err("Unknown configuration item");
+}
+
+static void
+cf_entry_compound(char *key, char *subkey, char *val)
+{
+  if (strncmp(key, "box", 3))
+    cf_err("Unknown configuration section");
+  int box_id = cf_int(key + 3);
+  struct cf_per_box *c = cf_per_box(box_id);
+
+  if (!strcmp(subkey, "cpus"))
+    c->cpus = cf_string(val);
+  else if (!strcmp(subkey, "mems"))
+    c->mems = cf_string(val);
+  else
+    cf_err("Unknown per-box configuration item");
+}
+
+static void
+cf_entry(char *key, char *val)
+{
+  char *dot = strchr(key, '.');
+  if (!dot)
+    cf_entry_toplevel(key, val);
+  else
+    {
+      *dot++ = 0;
+      cf_entry_compound(key, dot, val);
+    }
+}
+
+static void
+cf_check(void)
+{
+  if (!cf_box_root ||
+      !cf_cg_root ||
+      !cf_first_uid ||
+      !cf_first_gid ||
+      !cf_num_boxes)
+    cf_err("Configuration is not complete");
+}
+
+void
+cf_parse(void)
+{
+  FILE *f = fopen(CONFIG_FILE, "r");
+  if (!f)
+    die("Cannot open %s: %m", CONFIG_FILE);
+
+  char line[MAX_LINE_LEN];
+  while (fgets(line, sizeof(line), f))
+    {
+      line_number++;
+      char *nl = strchr(line, '\n');
+      if (!nl)
+	cf_err("Line not terminated or too long");
+      *nl = 0;
+
+      if (!line[0] || line[0] == '#')
+	continue;
+
+      char *s = line;
+      while (*s && *s != ' ' && *s != '\t' && *s != '=')
+	s++;
+      while (*s == ' ' || *s == '\t')
+	*s++ = 0;
+      if (*s != '=')
+	cf_err("Syntax error, expecting key=value");
+      *s++ = 0;
+      while (*s == ' ' || *s == '\t')
+	*s++ = 0;
+
+      cf_entry(line, s);
+    }
+
+  fclose(f);
+  cf_check();
+}
+
+struct cf_per_box *
+cf_per_box(int box_id)
+{
+  struct cf_per_box *c;
+
+  for (c = per_box_configs; c; c = c->next)
+    if (c->box_id == box_id)
+      return c;
+
+  c = xmalloc(sizeof(*c));
+  memset(c, 0, sizeof(*c));
+  c->next = per_box_configs;
+  per_box_configs = c;
+  c->box_id = box_id;
+  return c;
+}
+
+struct cf_per_box *
+cf_current_box(void)
+{
+  return cf_per_box(box_id);
+}