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ostree-prepare-root: Parse /proc/cmdline, make RPRIVATE, set up /sysroot 

This does everything we need except for the actual switch-root.
This commit is contained in:
Colin Walters 2013-06-02 21:41:08 -04:00
parent 1e080b9c73
commit 8eaaea795c
1 changed files with 69 additions and 20 deletions
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89
src/switchroot/ostree-prepare-root.c
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@ -64,6 +64,46 @@ perrorv (const char *format, ...)
return 0;
}
static void
parse_ostree_cmdline (char **out_osname,
char **out_tree)
{
FILE *f = fopen("/proc/cmdline", "r");
char *cmdline = NULL;
const char *iter;
size_t len;
if (!f)
return;
if (getline (&cmdline, &len, f) < 0)
return;
iter = cmdline;
while (iter != NULL)
{
const char *next = strchr (iter, ' ');
const char *next_nonspc = next;
while (*next_nonspc == ' ')
next_nonspc += 1;
if (strncmp (iter, "ostree=", strlen ("ostree=")) == 0)
{
const char *slash = strchr (iter, '/');
if (slash)
{
const char *start = iter + strlen ("ostree=");
*out_osname = strndup (start, slash - start);
if (next)
*out_tree = strndup (slash + 1, next - slash - 1);
else
*out_tree = strdup (slash + 1);
break;
}
}
iter = next_nonspc;
}
free (cmdline);
}
int
main(int argc, char *argv[])
{
@ -71,9 +111,8 @@ main(int argc, char *argv[])
const char *ostree_bind_mounts[] = { "/var", NULL };
const char *readonly_bind_mounts[] = { "/usr", NULL };
const char *root_mountpoint = NULL;
const char *ostree_target = NULL;
const char *p = NULL;
char *ostree_osname = NULL;
char *ostree_target = NULL;
char ostree_target_path[PATH_MAX];
char *deploy_path = NULL;
char srcpath[PATH_MAX];
@ -81,7 +120,6 @@ main(int argc, char *argv[])
struct stat stbuf;
size_t len;
int i;
int before_init_argc = 0;
if (argc < 3)
{
@ -89,33 +127,34 @@ main(int argc, char *argv[])
exit (1);
}
before_init_argc++;
root_mountpoint = argv[1];
before_init_argc++;
ostree_target = argv[2];
before_init_argc++;
p = strchr (ostree_target, '/');
if (p == NULL || p == ostree_target)
{
fprintf (stderr, "Malformed OSTree target %s; expected OSNAME/TREENAME\n", ostree_target);
exit (1);
}
ostree_osname = strndup (ostree_target, p - ostree_target);
parse_ostree_cmdline (&ostree_osname, &ostree_target);
snprintf (destpath, sizeof(destpath), "%s/ostree/deploy/%s",
root_mountpoint, ostree_target);
if (stat (destpath, &stbuf) < 0)
if (!ostree_osname)
{
perrorv ("Invalid OSTree root '%s'", destpath);
fprintf (stderr, "No OSTree target; expected ostree=OSNAME/TREENAME\n");
exit (1);
}
snprintf (destpath, sizeof(destpath), "%s/ostree/deploy/%s", root_mountpoint, ostree_target);
/* Work-around for a kernel bug: for some reason the kernel
* refuses switching root if any file systems are mounted
* MS_SHARED. Hence remount them MS_PRIVATE here as a
* work-around.
*
* https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
if (mount (NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)
{
perrorv ("Failed to make \"/\" private mount: %m");
exit (1);
}
snprintf (destpath, sizeof(destpath), "%s/ostree/deploy/%s/%s",
root_mountpoint, ostree_osname, ostree_target);
fprintf (stderr, "Examining %s\n", destpath);
if (lstat (destpath, &stbuf) < 0)
{
perrorv ("Second stat of OSTree root '%s' failed: ", destpath);
perrorv ("Couldn't find specified OSTree root '%s': ", destpath);
exit (1);
}
if (!S_ISLNK (stbuf.st_mode))
@ -194,6 +233,16 @@ main(int argc, char *argv[])
exit (1);
}
}
/* This is a bit hacky - move our deployment to /sysroot, since
* systemd's initrd-switch-root target hardcodes looking for it
* there.
*/
if (mount (deploy_path, root_mountpoint, NULL, MS_MOVE, NULL) < 0)
{
perrorv ("failed to MS_MOVE %s to %s", deploy_path, root_mountpoint);
exit (1);
}
exit (0);
}