From: Hadi Chokr <hadichokr@icloud.com>
Date: Fri, 12 Dec 2025 10:18:06 +0000 (+0100)
Subject: src/useradd: Support config for creating home dirs as Btrfs subvolumes
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3e8c105f0703264e947d8c034b90419794955d49;p=thirdparty%2Fshadow.git

src/useradd: Support config for creating home dirs as Btrfs subvolumes

Closes: #1162

Co-authored-by: Neal Gompa <ngompa@velocitylimitless.com>
Signed-off-by: Hadi Chokr <hadichokr@icloud.com>
Signed-off-by: Neal Gompa <ngompa@velocitylimitless.com>
Reviewed-by: Alejandro Colomar <alx@kernel.org>
---

diff --git a/man/useradd.8.xml b/man/useradd.8.xml
index e6db7f6d7..c745a6207 100644
--- a/man/useradd.8.xml
+++ b/man/useradd.8.xml
@@ -134,6 +134,33 @@
 	  </para>
 	</listitem>
       </varlistentry>
+      <varlistentry>
+	<term>
+	  <option>--btrfs-subvolume-home</option>
+	</term>
+	<listitem>
+	  <para>
+	    Create the user's home directory as a Btrfs subvolume.
+	  </para>
+	  <para>
+	    If this option is not specified,
+		<command>useradd</command> will follow the default behavior
+		defined by the <option>BTRFS_SUBVOLUME_HOME</option> variable
+		in <filename>/etc/default/useradd</filename>.
+	    If this variable is not set, the default value is no.
+	  </para>
+	  <para>
+	    When the <option>--btrfs-subvolume-home</option> command-line option
+	    is specified,
+		a Btrfs subvolume is created
+		regardless of any configuration file settings.
+	  </para>
+	  <para>
+	    Note: this feature works only if the underlying filesystem supports
+	    Btrfs subvolumes.
+	  </para>
+	</listitem>
+      </varlistentry>
       <varlistentry>
 	<term>
 	  <option>-c</option>, <option>--comment</option>&nbsp;<replaceable>COMMENT</replaceable>
diff --git a/src/useradd.c b/src/useradd.c
index 899efe3c8..8433ed8a8 100644
--- a/src/useradd.c
+++ b/src/useradd.c
@@ -114,6 +114,7 @@ static const char *def_shell = "/bin/bash";
 static const char *def_template = SKEL_DIR;
 static const char *def_usrtemplate = USRSKELDIR;
 static const char *def_create_mail_spool = "yes";
+static const char *def_btrfs_subvolume_home = "no";
 static const char *def_log_init = "yes";
 
 static long def_inactive = -1;
@@ -222,6 +223,7 @@ static bool home_added = false;
 #define DSKEL			"SKEL"
 #define DUSRSKEL		"USRSKEL"
 #define DCREATE_MAIL_SPOOL	"CREATE_MAIL_SPOOL"
+#define DBTRFS_SUBVOLUME_HOME	"BTRFS_SUBVOLUME_HOME"
 #define DLOG_INIT		"LOG_INIT"
 
 /* local function prototypes */
@@ -456,6 +458,7 @@ get_defaults(const struct option_flags *flags)
 				def_usrtemplate = xstrdup(ccp);
 			}
 		}
+
 		/*
 		 * Create by default user mail spool or not ?
 		 */
@@ -466,6 +469,15 @@ get_defaults(const struct option_flags *flags)
 			def_create_mail_spool = xstrdup(ccp);
 		}
 
+		/*
+		 * Create home directories as Btrfs subvolumes by default?
+		 */
+		else if (streq(buf, DBTRFS_SUBVOLUME_HOME)) {
+			if (streq(ccp, ""))
+				ccp = "no";
+			def_btrfs_subvolume_home = xstrdup(ccp);
+		}
+
 		/*
 		 * By default do we add the user to the lastlog and faillog databases ?
 		 */
@@ -500,6 +512,7 @@ static void show_defaults (void)
 	printf ("SKEL=%s\n", def_template);
 	printf ("USRSKEL=%s\n", def_usrtemplate);
 	printf ("CREATE_MAIL_SPOOL=%s\n", def_create_mail_spool);
+	printf ("BTRFS_SUBVOLUME_HOME=%s\n", def_btrfs_subvolume_home);
 	printf ("LOG_INIT=%s\n", def_log_init);
 }
 
@@ -523,6 +536,7 @@ set_defaults(void)
 	bool  out_skel = false;
 	bool  out_usrskel = false;
 	bool  out_create_mail_spool = false;
+	bool  out_btrfs_subvolume_home = false;
 	bool  out_log_init = false;
 	char  buf[1024];
 	char  *new_file = NULL;
@@ -639,6 +653,11 @@ set_defaults(void)
 			        DCREATE_MAIL_SPOOL "=%s\n",
 			        def_create_mail_spool);
 			out_create_mail_spool = true;
+		} else if (!out_btrfs_subvolume_home && streq(buf, DBTRFS_SUBVOLUME_HOME)) {
+			fprintf(ofp,
+			        DBTRFS_SUBVOLUME_HOME "=%s\n",
+			        def_btrfs_subvolume_home);
+			out_btrfs_subvolume_home = true;
 		} else if (!out_log_init && streq(buf, DLOG_INIT)) {
 			fprintf(ofp, DLOG_INIT "=%s\n", def_log_init);
 			out_log_init = true;
@@ -673,6 +692,8 @@ set_defaults(void)
 
 	if (!out_create_mail_spool)
 		fprintf (ofp, DCREATE_MAIL_SPOOL "=%s\n", def_create_mail_spool);
+	if (!out_btrfs_subvolume_home)
+		fprintf (ofp, DBTRFS_SUBVOLUME_HOME "=%s\n", def_btrfs_subvolume_home);
 	if (!out_log_init)
 		fprintf (ofp, DLOG_INIT "=%s\n", def_log_init);
 	/*
@@ -1431,6 +1452,9 @@ static void process_flags (int argc, char **argv, struct option_flags *flags)
 		}
 	}
 
+	if (!subvolflg && strcaseeq(def_btrfs_subvolume_home, "yes"))
+		subvolflg = true;
+
 	if (!gflg && !Nflg && !Uflg) {
 		/* Get the settings from login.defs */
 		Uflg = getdef_bool ("USERGROUPS_ENAB");