From: Hadi Chokr <hadichokr@icloud.com>
Date: Tue, 21 Apr 2026 07:18:19 +0000 (+0200)
Subject: useradd(8): fallback to regular dir for BTRFS home on non-BTRFS parent
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=7be9a6540f1cad477fd4f4e83d25904a5095bb86;p=thirdparty%2Fshadow.git

useradd(8): fallback to regular dir for BTRFS home on non-BTRFS parent

When the --btrfs-subvolume-home option is used but the parent directory
is not on a BTRFS filesystem, useradd previously failed with an error.
This is too strict; instead, fall back to creating a regular directory
and issue a warning.  The subvolume creation is attempted only when the
parent is BTRFS.  Otherwise, a regular directory is created and a
syslog(3) warning is logged.

Fixes: 3e8c105 (2026-01-02; "src/useradd: Support config for creating home dirs as Btrfs subvolumes")
Co-authored-by: Hadi Chokr <hadichokr@icloud.com>
Co-authored-by: Alejandro Colomar <alx@kernel.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
---

diff --git a/man/useradd.8.xml b/man/useradd.8.xml
index 8a087e13a..0bde6683d 100644
--- a/man/useradd.8.xml
+++ b/man/useradd.8.xml
@@ -2,6 +2,7 @@
 <!--
    SPDX-FileCopyrightText: 1991 - 1994, Julianne Frances Haugh
    SPDX-FileCopyrightText: 2007 - 2011, Nicolas François
+   SPDX-FileCopyrightText: 2025 - 2026, Hadi Chokr
    SPDX-License-Identifier: BSD-3-Clause
 -->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
@@ -156,8 +157,30 @@
 		regardless of any configuration file settings.
 	  </para>
 	  <para>
-	    Note: this feature works only if the underlying filesystem supports
-	    Btrfs subvolumes.
+	    If the parent directory of the user's home directory is
+	    <emphasis>not</emphasis> on a Btrfs filesystem,
+	    <command>useradd</command> will <emphasis>not</emphasis> create a
+	    subvolume.
+	    Instead, it creates a regular directory,
+	    prints a warning to standard error,
+	    and logs the event via syslog at level
+	    <constant>LOG_WARN</constant>.
+	    The user account is still created successfully.
+	  </para>
+	  <para>
+	    If the filesystem type cannot be determined (e.g., because of
+	    insufficient permissions, an I/O error,
+	    or a
+	    <citerefentry>
+	      <refentrytitle>statfs</refentrytitle>
+	      <manvolnum>2</manvolnum>
+	    </citerefentry>
+	    failure),
+	    <command>useradd</command> treats this as a fatal error:
+	    the home directory is not created,
+	    the command exits with a non‑zero status
+	    (<literal>E_HOMEDIR</literal>, 12),
+	    and an error message is printed.
 	  </para>
 	</listitem>
       </varlistentry>
diff --git a/src/useradd.c b/src/useradd.c
index 9bd32b11a..9210379c8 100644
--- a/src/useradd.c
+++ b/src/useradd.c
@@ -1,11 +1,11 @@
-/*
- * SPDX-FileCopyrightText: 1991 - 1994, Julianne Frances Haugh
- * SPDX-FileCopyrightText: 1996 - 2000, Marek Michałkiewicz
- * SPDX-FileCopyrightText: 2000 - 2006, Tomasz Kłoczko
- * SPDX-FileCopyrightText: 2007 - 2012, Nicolas François
- *
- * SPDX-License-Identifier: BSD-3-Clause
- */
+// SPDX-FileCopyrightText: 1991-1994, Julianne Frances Haugh
+// SPDX-FileCopyrightText: 1996-2000, Marek Michałkiewicz
+// SPDX-FileCopyrightText: 2000-2006, Tomasz Kłoczko
+// SPDX-FileCopyrightText: 2007-2012, Nicolas François
+// SPDX-FileCopyrightText: 2025-2026, Hadi Chokr
+// SPDX-FileCopyrightText: 2026, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
 
 #include "config.h"
 
@@ -2251,6 +2251,8 @@ static void create_home(const struct option_flags *flags)
 	   owner root:root.
 	 */
 	for (cp = strtok(bhome, "/"); cp != NULL; cp = strtok(NULL, "/")) {
+		bool  dir_created;
+
 		/* Avoid turning a relative path into an absolute path. */
 		if (strprefix(bhome, "/") || !streq(path, ""))
 			strcat(path, "/");
@@ -2260,10 +2262,7 @@ static void create_home(const struct option_flags *flags)
 			continue;
 		}
 
-		/* Check if parent directory is BTRFS, fail if requesting
-		   subvolume but no BTRFS. The paths could be different by the
-		   trailing slash
-		 */
+		dir_created = false;
 #if WITH_BTRFS
 		if (subvolflg && (strlen(prefix_user_home) - (int)strlen(path)) <= 1) {
 			char *btrfs_check = strdup(path);
@@ -2284,25 +2283,26 @@ static void create_home(const struct option_flags *flags)
 			free(btrfs_check);
 			if (!is_btrfs(&sfs)) {
 				fprintf(stderr,
-					_("%s: home directory \"%s\" must be mounted on BTRFS\n"),
-					Prog, path);
-				fail_exit(E_HOMEDIR, process_selinux);
+				        _("%s: warning: \"%s\" is not on BTRFS; creating regular directory instead of subvolume\n"),
+				        Prog, prefix_user_home);
+			} else {
+				if (btrfs_create_subvolume(path)) {
+					fprintf(stderr,
+					        _("%s: failed to create BTRFS subvolume: %s\n"),
+						Prog, path);
+					fail_exit(E_HOMEDIR, process_selinux);
+				}
+				dir_created = true;
 			}
-			// make subvolume to mount for user instead of directory
-			if (btrfs_create_subvolume(path)) {
-				fprintf(stderr,
-					_("%s: failed to create BTRFS subvolume: %s\n"),
+		}
+#endif
+		if (!dir_created) {
+			if (mkdir(path, 0) != 0) {
+				fprintf(stderr, _("%s: cannot create directory %s\n"),
 					Prog, path);
 				fail_exit(E_HOMEDIR, process_selinux);
 			}
 		}
-		else
-#endif
-		if (mkdir(path, 0) != 0) {
-			fprintf(stderr, _("%s: cannot create directory %s\n"),
-				Prog, path);
-			fail_exit(E_HOMEDIR, process_selinux);
-		}
 		if (chown(path, 0, 0) < 0) {
 			fprintf(stderr,
 				_("%s: warning: chown on `%s' failed: %m\n"),