Allow to configure path of external tools

HISTORY

@@ -29,6 +29,11 @@ SnapRAID HISTORY
    will be slower, this change preserves hash data in the content file
    to ensure a better fix during disk failures and allows the --import
    option to remain functional even after an incomplete sync.
+ * Added --with-smartctl, --with-zfs, --with-zpool, --with-bcachefs
+   configure options to allow pinning the absolute path of each tool at
+   build time. When not specified, the existing runtime discovery
+   behaviour is preserved. Primarily intended for NixOS and other
+   non-FHS systems.
 
 14.6 2026/06
 ============

cmdline/unix.c

@@ -611,6 +611,10 @@ int exit_sync_needed = 2;
 
 #if HAVE_LINUX_DEVICE
 static const char* const bcachefs_paths[] = {
+#ifdef BCACHEFS_PATH
+	/* Path configured at build time (e.g. on NixOS). */
+	BCACHEFS_PATH,
+#else
 	"/usr/sbin/bcachefs",
 	"/sbin/bcachefs",
 	"/usr/local/sbin/bcachefs",
@@ -620,6 +624,7 @@ static const char* const bcachefs_paths[] = {
 #ifdef __APPLE__
 	/* macOS (Intel & Apple Silicon) */
 	"/opt/homebrew/sbin/bcachefs",
+#endif
 #endif
 	0
 };
@@ -638,6 +643,10 @@ static const char* find_bcachefs(void)
 
 #if HAVE_LINUX_DEVICE
 static const char* const zfs_paths[] = {
+#ifdef ZFS_PATH
+	/* Path configured at build time (e.g. on NixOS). */
+	ZFS_PATH,
+#else
 	"/usr/sbin/zfs",
 	"/sbin/zfs",
 	"/usr/local/sbin/zfs",
@@ -647,6 +656,7 @@ static const char* const zfs_paths[] = {
 #ifdef __APPLE__
 	/* macOS (Intel & Apple Silicon) */
 	"/opt/homebrew/sbin/zfs",
+#endif
 #endif
 	0
 };
@@ -662,6 +672,10 @@ static const char* find_zfs(void)
 }
 
 static const char* const zpool_paths[] = {
+#ifdef ZPOOL_PATH
+	/* Path configured at build time (e.g. on NixOS). */
+	ZPOOL_PATH,
+#else
 	"/usr/sbin/zpool",
 	"/sbin/zpool",
 	"/usr/local/sbin/zpool",
@@ -671,6 +685,7 @@ static const char* const zpool_paths[] = {
 #ifdef __APPLE__
 	/* macOS (Intel & Apple Silicon) */
 	"/opt/homebrew/sbin/zpool",
+#endif
 #endif
 	0
 };
@@ -782,7 +797,12 @@ const char* stat_desc(struct stat* st)
 }
 
 #if HAVE_LINUX_DEVICE
+
 static const char* smartctl_paths[] = {
+#ifdef SMARTCTL_PATH
+	/* Path configured at build time (e.g. on NixOS). */
+	SMARTCTL_PATH,
+#else
 	/* Linux & BSD */
 	"/usr/sbin/smartctl",
 	"/sbin/smartctl",
@@ -792,6 +812,7 @@ static const char* smartctl_paths[] = {
 #ifdef __APPLE__
 	/* macOS (Intel & Apple Silicon) */
 	"/opt/homebrew/sbin/smartctl",
+#endif
 #endif
 	0
 };

configure.ac

@@ -456,6 +456,32 @@ AC_ARG_ENABLE([warning],
 	],
 	[])
 
+# WITH_TOOL(NAME, BINARY, DESCRIPTION)
+# Adds --with-NAME=PATH option. Defines NAME_PATH if given.
+AC_DEFUN([WITH_TOOL], [
+    AC_ARG_WITH([$1],
+        [AS_HELP_STRING([--with-$1=PATH],
+            [absolute path to the $2 executable ($3)])],
+        [
+            AS_CASE([$withval],
+                [/*], [],
+                [AC_MSG_ERROR([--with-$1 requires an absolute path (got '$withval')])])
+            AS_IF([test ! -x "$withval"],
+                [AC_MSG_WARN([$2 not found or not executable at '$withval'])])
+            AC_DEFINE_UNQUOTED(m4_toupper([$1_PATH]), ["$withval"], 
+                [Absolute path to $2, set at configure time.])
+            AC_MSG_NOTICE([$2: $withval])
+        ],
+        [
+            AC_MSG_NOTICE([$2: use runtime discovery])
+        ])
+])
+
+WITH_TOOL([smartctl], [smartctl],  [S.M.A.R.T. monitoring])
+WITH_TOOL([zfs], [zfs], [ZFS pool management])
+WITH_TOOL([zpool], [zpool], [ZFS pool status])
+WITH_TOOL([bcachefs], [bcachefs], [Bcachefs management])
+
 AC_ARG_VAR([TESTENV], [Test environment])
 AC_ARG_VAR([FAILENV], [Test environment for failing tests])
 AC_ARG_VAR([TESTENV_SSE2], [Test environment for SSE2])