[libvirt] [sandbox 07/10] qemu: use mounts targeting / as root
So far a mount with / as target doesn't change anything: the host / is
still the one mounted as /. libvirt-sandbox-init-qemu now detects the
presence of a / target in mounts.cfg and mounts it instead of
sandbox:root.
---
libvirt-sandbox/libvirt-sandbox-init-qemu.c | 69 ++++++++++++++++++++++++++++-
1 file changed, 67 insertions(+), 2 deletions(-)
diff --git a/libvirt-sandbox/libvirt-sandbox-init-qemu.c
b/libvirt-sandbox/libvirt-sandbox-init-qemu.c
index 9acea5f..02fb980 100644
--- a/libvirt-sandbox/libvirt-sandbox-init-qemu.c
+++ b/libvirt-sandbox/libvirt-sandbox-init-qemu.c
@@ -264,6 +264,70 @@ mount_entry(const char *source,
}
}
+static void
+mount_root(const char *path)
+{
+ int foundRoot = 0;
+
+ /* Loop over mounts.cfg to see if we have a candidate for / */
+ mount_mkdir(SANDBOXCONFIGDIR, 0755);
+ mount_9pfs("sandbox:config", SANDBOXCONFIGDIR, 0755, 1);
+
+ FILE *fp = fopen(SANDBOXCONFIGDIR "/mounts.cfg", "r");
+ while (fgets(line, sizeof line, fp) && !foundRoot) {
+ char *source = line;
+ char *target = strchr(source, '\t');
+ *target = '\0';
+ target++;
+ char *type = strchr(target, '\t');
+ *type = '\0';
+ type++;
+ char *opts = strchr(type, '\t');
+ *opts = '\0';
+ opts++;
+ char *tmp = strchr(opts, '\n');
+ *tmp = '\0';
+
+ if (STREQ(target, "/")) {
+ int needsDev = strncmp(source, "/dev/", 5) == 0;
+
+ if (debug)
+ fprintf(stderr, "libvirt-sandbox-init-qemu: found root from
%s\n",
+ source);
+
+ /* In this case, we need to have a /dev before the chroot */
+ if (needsDev) {
+ mount_other("/proc", "proc", 0755);
+ mount_other("/dev", "tmpfs", 0755);
+ }
+
+ mount_entry(source, path, type, opts);
+
+ if (needsDev && umount("/dev") < 0) {
+ fprintf(stderr,
+ "libvirt-sandbox-init-qemu: %s: "
+ "cannot unmount temporary /dev: %s\n",
+ __func__, strerror(errno));
+ exit_poweroff();
+ }
+ foundRoot = 1;
+ }
+ }
+ fclose(fp);
+
+ if (umount(SANDBOXCONFIGDIR) < 0) {
+ fprintf(stderr,
+ "libvirt-sandbox-init-qemu: %s: "
+ "cannot unmount temporary %s: %s\n",
+ __func__, SANDBOXCONFIGDIR, strerror(errno));
+ exit_poweroff();
+ }
+
+ /* If we couldn't get a / in the mounts, then use the host one */
+ if (!foundRoot)
+ mount_9pfs("sandbox:root", path, 0755, 1);
+}
+
int
main(int argc ATTR_UNUSED, char **argv ATTR_UNUSED)
{
@@ -308,7 +372,7 @@ main(int argc ATTR_UNUSED, char **argv ATTR_UNUSED)
if (debug)
fprintf(stderr, "libvirt-sandbox-init-qemu: mounting new root on
/tmproot\n");
- mount_9pfs("sandbox:root", "/tmproot", 0755, 1);
+ mount_root("/tmproot");
/* Note that pivot_root won't work. See the note in
* Documentation/filesystems/ramfs-rootfs-initramfs.txt
@@ -412,7 +476,8 @@ main(int argc ATTR_UNUSED, char **argv ATTR_UNUSED)
fprintf(stderr, "libvirt-sandbox-init-qemu: %s: %s -> %s (%s,
%s)\n",
__func__, source, target, type, opts);
- mount_entry(source, target, type, opts);
+ if (STREQ(target, "/"))
+ mount_entry(source, target, type, opts);
}
fclose(fp);
--
2.1.4