diff --git a/sbin/fsdb/fsdb.c b/sbin/fsdb/fsdb.c
index 5b179970a08e..ffffa389a206 100644
--- a/sbin/fsdb/fsdb.c
+++ b/sbin/fsdb/fsdb.c
@@ -109,6 +109,8 @@ main(int argc, char *argv[])
 	sblock_init();
 	if (!setup(fsys))
 		errx(1, "cannot set up file system `%s'", fsys);
+	if (fswritefd < 0)
+		nflag++;
 	printf("%s file system `%s'\nLast Mounted on %s\n",
 	       nflag? "Examining": "Editing", fsys, sblock.fs_fsmnt);
 	rval = cmdloop();
diff --git a/sbin/fsdb/fsdbutil.c b/sbin/fsdb/fsdbutil.c
index fb7929913209..2c18d9910c6f 100644
--- a/sbin/fsdb/fsdbutil.c
+++ b/sbin/fsdb/fsdbutil.c
@@ -53,7 +53,7 @@ static const char rcsid[] =
 #include "fsdb.h"
 #include "fsck.h"
 
-void prtblknos(struct uufsd *disk, union dinode *dp);
+void prtblknos(struct fs *fs, union dinode *dp);
 
 char **
 crack(char *line, int *argc)
@@ -236,7 +236,7 @@ printactive(int doblocks)
     case IFSOCK:
     case IFIFO:
 	if (doblocks)
-	    prtblknos(&disk, curinode);
+	    prtblknos(&sblock, curinode);
 	else
 	    printstat("current inode", curinum, curinode);
 	break;
diff --git a/tools/diag/prtblknos/Makefile b/tools/diag/prtblknos/Makefile
index a813bb6a2fd0..385692c820ca 100644
--- a/tools/diag/prtblknos/Makefile
+++ b/tools/diag/prtblknos/Makefile
@@ -11,6 +11,8 @@ LIBADD+=ufs
 
 WARNS?=	3
 
+CFLAGS+=-DPRTBLKNOS
+
 test:	${PROG}
 	./${PROG} > a
 
diff --git a/tools/diag/prtblknos/main.c b/tools/diag/prtblknos/main.c
index c3abb2babad1..25a717760922 100644
--- a/tools/diag/prtblknos/main.c
+++ b/tools/diag/prtblknos/main.c
@@ -39,14 +39,15 @@ union dinode {
 	struct ufs2_dinode *dp2;
 };
 
-void prtblknos(struct uufsd *disk, union dinode *dp);
+void prtblknos(struct fs *fs, union dinode *dp);
+
+struct uufsd disk;
 
 int
 main(argc, argv)
 	int argc;
 	char *argv[];
 {
-	struct uufsd disk;
 	union dinodep dp;
 	struct fs *fs;
 	struct stat sb;
@@ -102,7 +103,7 @@ main(argc, argv)
 			warn("Read of inode %jd on %s failed: %s",
 			    (intmax_t)inonum, fsname, disk.d_error);
 
-		prtblknos(&disk, (union dinode *)dp.dp1);
+		prtblknos(fs, (union dinode *)dp.dp1);
 	}
 	exit(0);
 }
diff --git a/tools/diag/prtblknos/prtblknos.c b/tools/diag/prtblknos/prtblknos.c
index f042bae606f1..771d79e43ec9 100644
--- a/tools/diag/prtblknos/prtblknos.c
+++ b/tools/diag/prtblknos/prtblknos.c
@@ -31,32 +31,37 @@
 
 #include <err.h>
 #include <stdio.h>
+#include <string.h>
 #include <libufs.h>
 
+#ifdef PRTBLKNOS
 union dinode {
 	struct ufs1_dinode dp1;
 	struct ufs2_dinode dp2;
 };
+extern struct uufsd disk;
+#else /* used by fsdb */
+#include <fsck.h>
+static struct bufarea *bp;
+#endif
 
-void prtblknos(struct uufsd *disk, union dinode *dp);
+void prtblknos(struct fs *fs, union dinode *dp);
 
 static const char *distance(struct fs *, ufs2_daddr_t, ufs2_daddr_t);
 static void  printblk(struct fs *, ufs_lbn_t, ufs2_daddr_t, int, ufs_lbn_t);
-static void  indirprt(struct uufsd *, int, ufs_lbn_t, ufs_lbn_t, ufs2_daddr_t,
+static void  indirprt(struct fs *, int, ufs_lbn_t, ufs_lbn_t, ufs2_daddr_t,
 		ufs_lbn_t);
 
 void
-prtblknos(disk, dp)
-	struct uufsd *disk;
+prtblknos(fs, dp)
+	struct fs *fs;
 	union dinode *dp;
 {
 	int i, mode, frags;
 	ufs_lbn_t lbn, lastlbn, len, blksperindir;
 	ufs2_daddr_t blkno;
-	struct fs *fs;
 	off_t size;
 
-	fs = (struct fs *)&disk->d_sb;
 	if (fs->fs_magic == FS_UFS1_MAGIC) {
 		size = dp->dp1.di_size;
 		mode = dp->dp1.di_mode;
@@ -138,7 +143,7 @@ prtblknos(disk, dp)
 			blkno = dp->dp1.di_ib[i];
 		else
 			blkno = dp->dp2.di_ib[i];
-		indirprt(disk, i, blksperindir, lbn, blkno, lastlbn);
+		indirprt(fs, i, blksperindir, lbn, blkno, lastlbn);
 		blksperindir *= NINDIR(fs);
 		lbn += blksperindir;
 		len -= blksperindir;
@@ -149,8 +154,8 @@ prtblknos(disk, dp)
 }
 
 static void
-indirprt(disk, level, blksperindir, lbn, blkno, lastlbn)
-	struct uufsd *disk;
+indirprt(fs, level, blksperindir, lbn, blkno, lastlbn)
+	struct fs *fs;
 	int level;
 	ufs_lbn_t blksperindir;
 	ufs_lbn_t lbn;
@@ -158,10 +163,8 @@ indirprt(disk, level, blksperindir, lbn, blkno, lastlbn)
 	ufs_lbn_t lastlbn;
 {
 	char indir[MAXBSIZE];
-	struct fs *fs;
 	ufs_lbn_t i, last;
 
-	fs = (struct fs *)&disk->d_sb;
 	if (blkno == 0) {
 		printblk(fs, lbn, blkno,
 		    blksperindir * NINDIR(fs) * fs->fs_frag, lastlbn);
@@ -169,7 +172,14 @@ indirprt(disk, level, blksperindir, lbn, blkno, lastlbn)
 	}
 	printblk(fs, lbn, blkno, fs->fs_frag, -level);
 	/* read in the indirect block. */
-	if (bread(disk, fsbtodb(fs, blkno), indir, fs->fs_bsize) == -1) {
+#ifdef PRTBLKNOS
+	if (bread(&disk, fsbtodb(fs, blkno), indir, fs->fs_bsize) == -1) {
+#else /* used by fsdb */
+	bp = getdatablk(blkno, fs->fs_bsize, BT_LEVEL1 + level);
+	if (bp->b_errs == 0) {
+		memcpy(indir, bp->b_un.b_buf, fs->fs_bsize);
+	} else {
+#endif
 		warn("Read of indirect block %jd failed", (intmax_t)blkno);
 		/* List the unreadable part as a hole */
 		printblk(fs, lbn, 0,
@@ -193,7 +203,7 @@ indirprt(disk, level, blksperindir, lbn, blkno, lastlbn)
 			blkno = ((ufs1_daddr_t *)indir)[i];
 		else
 			blkno = ((ufs2_daddr_t *)indir)[i];
-		indirprt(disk, level - 1, blksperindir / NINDIR(fs),
+		indirprt(fs, level - 1, blksperindir / NINDIR(fs),
 		    lbn + blksperindir * i, blkno, lastlbn);
 	}
 }