diff options
Diffstat (limited to 'src/nspawn/nspawn-mount.c')
| -rw-r--r-- | src/nspawn/nspawn-mount.c | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c index 72c007f204..4b2838b752 100644 --- a/src/nspawn/nspawn-mount.c +++ b/src/nspawn/nspawn-mount.c @@ -1349,3 +1349,116 @@ fail: (void) rmdir(template); return r; } + +/* Expects *pivot_root_new and *pivot_root_old to be initialised to allocated memory or NULL. */ +int pivot_root_parse(char **pivot_root_new, char **pivot_root_old, const char *s) { + _cleanup_free_ char *root_new = NULL, *root_old = NULL; + const char *p = s; + int r; + + assert(pivot_root_new); + assert(pivot_root_old); + + r = extract_first_word(&p, &root_new, ":", EXTRACT_DONT_COALESCE_SEPARATORS); + if (r < 0) + return r; + if (r == 0) + return -EINVAL; + + if (isempty(p)) + root_old = NULL; + else { + root_old = strdup(p); + if (!root_old) + return -ENOMEM; + } + + if (!path_is_absolute(root_new)) + return -EINVAL; + if (root_old && !path_is_absolute(root_old)) + return -EINVAL; + + free_and_replace(*pivot_root_new, root_new); + free_and_replace(*pivot_root_old, root_old); + + return 0; +} + +int setup_pivot_root(const char *directory, const char *pivot_root_new, const char *pivot_root_old) { + _cleanup_free_ char *directory_pivot_root_new = NULL; + _cleanup_free_ char *pivot_tmp_pivot_root_old = NULL; + char pivot_tmp[] = "/tmp/nspawn-pivot-XXXXXX"; + bool remove_pivot_tmp = false; + int r; + + assert(directory); + + if (!pivot_root_new) + return 0; + + /* Pivot pivot_root_new to / and the existing / to pivot_root_old. + * If pivot_root_old is NULL, the existing / disappears. + * This requires a temporary directory, pivot_tmp, which is + * not a child of either. + * + * This is typically used for OSTree-style containers, where + * the root partition contains several sysroots which could be + * run. Normally, one would be chosen by the bootloader and + * pivoted to / by initramfs. + * + * For example, for an OSTree deployment, pivot_root_new + * would be: /ostree/deploy/$os/deploy/$checksum. Note that this + * code doesn’t do the /var mount which OSTree expects: use + * --bind +/sysroot/ostree/deploy/$os/var:/var for that. + * + * So in the OSTree case, we’ll end up with something like: + * - directory = /tmp/nspawn-root-123456 + * - pivot_root_new = /ostree/deploy/os/deploy/123abc + * - pivot_root_old = /sysroot + * - directory_pivot_root_new = + * /tmp/nspawn-root-123456/ostree/deploy/os/deploy/123abc + * - pivot_tmp = /tmp/nspawn-pivot-123456 + * - pivot_tmp_pivot_root_old = /tmp/nspawn-pivot-123456/sysroot + * + * Requires all file systems at directory and below to be mounted + * MS_PRIVATE or MS_SLAVE so they can be moved. + */ + directory_pivot_root_new = prefix_root(directory, pivot_root_new); + + /* Remount directory_pivot_root_new to make it movable. */ + r = mount_verbose(LOG_ERR, directory_pivot_root_new, directory_pivot_root_new, NULL, MS_BIND, NULL); + if (r < 0) + goto done; + + if (pivot_root_old) { + if (!mkdtemp(pivot_tmp)) { + r = log_error_errno(errno, "Failed to create temporary directory: %m"); + goto done; + } + + remove_pivot_tmp = true; + pivot_tmp_pivot_root_old = prefix_root(pivot_tmp, pivot_root_old); + + r = mount_verbose(LOG_ERR, directory_pivot_root_new, pivot_tmp, NULL, MS_MOVE, NULL); + if (r < 0) + goto done; + + r = mount_verbose(LOG_ERR, directory, pivot_tmp_pivot_root_old, NULL, MS_MOVE, NULL); + if (r < 0) + goto done; + + r = mount_verbose(LOG_ERR, pivot_tmp, directory, NULL, MS_MOVE, NULL); + if (r < 0) + goto done; + } else { + r = mount_verbose(LOG_ERR, directory_pivot_root_new, directory, NULL, MS_MOVE, NULL); + if (r < 0) + goto done; + } + +done: + if (remove_pivot_tmp) + (void) rmdir(pivot_tmp); + + return r; +} |