To get GEOM Eli working in our project (http://www.freenas.org) I had
to enhance the geli userland application. The original code does not
support non-interactive scripting, e.g. when creating or initializing
GEOM Eli filesystem, because the password has to be entered interactively
on the console. Because our project is administrated via WebGUI it is
not possible to do that. With the patch you can enter the password non-
interactively as following:

(/bin/echo $passphrase; /bin/echo $passphrase) | /sbin/geli init -t -v -e $ealgo $disk

The code has been taken from the Samba tool 'smbpasswd'. The patch itself
has been done for CURRENT.

I think this is also useful for other users.

Greetings
Volker

/usr/src/sbin/geom/class/eli:

--- geom_eli.c.orig	Mon Aug  6 10:18:42 2007
+++ geom_eli.c	Mon Aug  6 10:36:02 2007
@@ -73,13 +73,15 @@
 static void eli_restore(struct gctl_req *req);
 static void eli_clear(struct gctl_req *req);
 static void eli_dump(struct gctl_req *req);
+static char *eli_get_passwd(struct gctl_req *, const char *, char *, size_t);
+static char *eli_get_stdin_passwd(void);
 
 /*
  * Available commands:
  *
- * init [-bhPv] [-a aalgo] [-e ealgo] [-i iterations] [-l keylen] [-K newkeyfile] prov
+ * init [-bhPtv] [-a aalgo] [-e ealgo] [-i iterations] [-l keylen] [-K newkeyfile] prov
  * label - alias for 'init'
- * attach [-dprv] [-k keyfile] prov
+ * attach [-dprtv] [-k keyfile] prov
  * detach [-fl] prov ...
  * stop - alias for 'detach'
  * onetime [-d] [-a aalgo] [-e ealgo] [-l keylen] prov ...
@@ -103,9 +105,10 @@
 		{ 'l', "keylen", &keylen, G_TYPE_NUMBER },
 		{ 'P', "nonewpassphrase", NULL, G_TYPE_BOOL },
 		{ 's', "sectorsize", &sectorsize, G_TYPE_NUMBER },
+		{ 't', "password-from-stdin", NULL, G_TYPE_NONE },
 		G_OPT_SENTINEL
 	    },
-	    NULL, "[-bPv] [-a aalgo] [-e ealgo] [-i iterations] [-l keylen] [-K newkeyfile] [-s sectorsize] prov"
+	    NULL, "[-bPtv] [-a aalgo] [-e ealgo] [-i iterations] [-l keylen] [-K newkeyfile] [-s sectorsize] prov"
 	},
 	{ "label", G_FLAG_VERBOSE, eli_main,
 	    {
@@ -117,6 +120,7 @@
 		{ 'l', "keylen", &keylen, G_TYPE_NUMBER },
 		{ 'P', "nonewpassphrase", NULL, G_TYPE_BOOL },
 		{ 's', "sectorsize", &sectorsize, G_TYPE_NUMBER },
+		{ 't', "password-from-stdin", NULL, G_TYPE_NONE },
 		G_OPT_SENTINEL
 	    },
 	    NULL, "- an alias for 'init'"
@@ -127,9 +131,10 @@
 		{ 'k', "keyfile", keyfile, G_TYPE_STRING },
 		{ 'p', "nopassphrase", NULL, G_TYPE_BOOL },
 		{ 'r', "readonly", NULL, G_TYPE_BOOL },
+		{ 't', "password-from-stdin", NULL, G_TYPE_NONE },
 		G_OPT_SENTINEL
 	    },
-	    NULL, "[-dprv] [-k keyfile] prov"
+	    NULL, "[-dprtv] [-k keyfile] prov"
 	},
 	{ "detach", 0, NULL,
 	    {
@@ -174,9 +179,10 @@
 		{ 'n', "keyno", &keyno, G_TYPE_NUMBER },
 		{ 'p', "nopassphrase", NULL, G_TYPE_BOOL },
 		{ 'P', "nonewpassphrase", NULL, G_TYPE_BOOL },
+		{ 't', "password-from-stdin", NULL, G_TYPE_NONE },
 		G_OPT_SENTINEL
 	    },
-	    NULL, "[-pPv] [-n keyno] [-i iterations] [-k keyfile] [-K newkeyfile] prov"
+	    NULL, "[-pPtv] [-n keyno] [-i iterations] [-k keyfile] [-K newkeyfile] prov"
 	},
 	{ "delkey", G_FLAG_VERBOSE, eli_main,
 	    {
@@ -359,9 +365,9 @@
 			return (NULL);
 		}
 		for (;;) {
-			p = readpassphrase(
-			    new ? "Enter new passphrase:" : "Enter passphrase:",
-			    buf1, sizeof(buf1), RPP_ECHO_OFF | RPP_REQUIRE_TTY);
+			p = eli_get_passwd(req,
+			    new ? "Enter new passphrase: " : "Enter passphrase: ",
+			    buf1, sizeof(buf1));
 			if (p == NULL) {
 				bzero(buf1, sizeof(buf1));
 				gctl_error(req, "Cannot read passphrase: %s.",
@@ -370,9 +376,8 @@
 			}
 	
 			if (new) {
-				p = readpassphrase("Reenter new passphrase: ",
-				    buf2, sizeof(buf2),
-				    RPP_ECHO_OFF | RPP_REQUIRE_TTY);
+				p = eli_get_passwd(req, "Reenter new passphrase: ",
+				    buf2, sizeof(buf2));
 				if (p == NULL) {
 					bzero(buf1, sizeof(buf1));
 					gctl_error(req,
@@ -383,7 +388,11 @@
 	
 				if (strcmp(buf1, buf2) != 0) {
 					bzero(buf2, sizeof(buf2));
-					fprintf(stderr, "They didn't match.\n");
+					gctl_error(req, "Passphrases didn't match.");
+					/* Exit immediately if reading passwords from stdin. */
+					if (gctl_get_int(req, "password-from-stdin")) {
+						return (NULL);
+					}
 					continue;
 				}
 				bzero(buf2, sizeof(buf2));
@@ -1244,3 +1253,42 @@
 		printf("\n");
 	}
 }
+
+static char *
+eli_get_passwd(struct gctl_req *req, const char *prompt, char *buf, size_t bufsiz)
+{
+	char *p = NULL;
+
+	if (gctl_get_int(req, "password-from-stdin")) {
+		p = eli_get_stdin_passwd();
+		strlcpy(buf, p, bufsiz);
+	} else {
+		p = readpassphrase(prompt, buf, bufsiz, RPP_ECHO_OFF | RPP_REQUIRE_TTY);
+	}
+
+	return p;
+}
+
+static char *
+eli_get_stdin_passwd(void)
+{
+	static char buf[BUFSIZ];
+	size_t len;
+
+	bzero(buf, sizeof(buf));
+
+	/*
+	 * if no error is reported from fgets() and string at least contains
+	 * the newline that ends the password, then replace the newline with
+	 * a null terminator.
+	 */
+	if (fgets(buf, sizeof(buf), stdin) != NULL) {
+		if ((len = strlen(buf)) > 0) {
+			if (buf[len-1] == '\n')
+				buf[len - 1] = 0;
+		}
+	}
+
+	return buf;
+}
+