diff --git a/kmod/src/alloc.c b/kmod/src/alloc.c
index 1adbcd37..d62b2f58 100644
--- a/kmod/src/alloc.c
+++ b/kmod/src/alloc.c
@@ -977,6 +977,39 @@ int scoutfs_alloc_move(struct super_block *sb, struct scoutfs_alloc *alloc,
 	return ret;
 }
 
+/*
+ * Add new free space to an allocator.  _ext_insert will make sure that it doesn't
+ * overlap with any existing extents.  This is done by the server in a transaction that
+ * also updates total_*_blocks in the super so we don't verify.
+ */
+int scoutfs_alloc_insert(struct super_block *sb, struct scoutfs_alloc *alloc,
+			 struct scoutfs_block_writer *wri, struct scoutfs_alloc_root *root,
+			 u64 start, u64 len)
+{
+	struct alloc_ext_args args = {
+		.alloc = alloc,
+		.wri = wri,
+		.root = root,
+		.zone = SCOUTFS_FREE_EXTENT_BLKNO_ZONE,
+	};
+
+	return scoutfs_ext_insert(sb, &alloc_ext_ops, &args, start, len, 0, 0);
+}
+
+int scoutfs_alloc_remove(struct super_block *sb, struct scoutfs_alloc *alloc,
+			 struct scoutfs_block_writer *wri, struct scoutfs_alloc_root *root,
+			 u64 start, u64 len)
+{
+	struct alloc_ext_args args = {
+		.alloc = alloc,
+		.wri = wri,
+		.root = root,
+		.zone = SCOUTFS_FREE_EXTENT_BLKNO_ZONE,
+	};
+
+	return scoutfs_ext_remove(sb, &alloc_ext_ops, &args, start, len);
+}
+
 /*
  * We only trim one block, instead of looping trimming all, because the
  * caller is assuming that we do a fixed amount of work when they check
diff --git a/kmod/src/alloc.h b/kmod/src/alloc.h
index 5a95d98c..9dcbd94c 100644
--- a/kmod/src/alloc.h
+++ b/kmod/src/alloc.h
@@ -132,6 +132,12 @@ int scoutfs_alloc_move(struct super_block *sb, struct scoutfs_alloc *alloc,
 		       struct scoutfs_alloc_root *dst,
 		       struct scoutfs_alloc_root *src, u64 total,
 		       __le64 *exclusive, __le64 *vacant, u64 zone_blocks);
+int scoutfs_alloc_insert(struct super_block *sb, struct scoutfs_alloc *alloc,
+			 struct scoutfs_block_writer *wri, struct scoutfs_alloc_root *root,
+			 u64 start, u64 len);
+int scoutfs_alloc_remove(struct super_block *sb, struct scoutfs_alloc *alloc,
+			 struct scoutfs_block_writer *wri, struct scoutfs_alloc_root *root,
+			 u64 start, u64 len);
 
 int scoutfs_alloc_fill_list(struct super_block *sb,
 			    struct scoutfs_alloc *alloc,
diff --git a/kmod/src/client.c b/kmod/src/client.c
index 9fcc2a2d..20dad9e0 100644
--- a/kmod/src/client.c
+++ b/kmod/src/client.c
@@ -297,6 +297,14 @@ int scoutfs_client_clear_volopt(struct super_block *sb, struct scoutfs_volume_op
 					volopt, sizeof(*volopt), NULL, 0);
 }
 
+int scoutfs_client_resize_devices(struct super_block *sb, struct scoutfs_net_resize_devices *nrd)
+{
+	struct client_info *client = SCOUTFS_SB(sb)->client_info;
+
+	return scoutfs_net_sync_request(sb, client->conn, SCOUTFS_NET_CMD_RESIZE_DEVICES,
+					nrd, sizeof(*nrd), NULL, 0);
+}
+
 /* The client is receiving a invalidation request from the server */
 static int client_lock(struct super_block *sb,
 		       struct scoutfs_net_connection *conn, u8 cmd, u64 id,
diff --git a/kmod/src/client.h b/kmod/src/client.h
index 1cbcbc1d..e62eccae 100644
--- a/kmod/src/client.h
+++ b/kmod/src/client.h
@@ -33,6 +33,7 @@ int scoutfs_client_open_ino_map(struct super_block *sb, u64 group_nr,
 int scoutfs_client_get_volopt(struct super_block *sb, struct scoutfs_volume_options *volopt);
 int scoutfs_client_set_volopt(struct super_block *sb, struct scoutfs_volume_options *volopt);
 int scoutfs_client_clear_volopt(struct super_block *sb, struct scoutfs_volume_options *volopt);
+int scoutfs_client_resize_devices(struct super_block *sb, struct scoutfs_net_resize_devices *nrd);
 
 int scoutfs_client_setup(struct super_block *sb);
 void scoutfs_client_destroy(struct super_block *sb);
diff --git a/kmod/src/format.h b/kmod/src/format.h
index 39fdddd2..3f0fff1a 100644
--- a/kmod/src/format.h
+++ b/kmod/src/format.h
@@ -986,6 +986,7 @@ enum scoutfs_net_cmd {
 	SCOUTFS_NET_CMD_GET_VOLOPT,
 	SCOUTFS_NET_CMD_SET_VOLOPT,
 	SCOUTFS_NET_CMD_CLEAR_VOLOPT,
+	SCOUTFS_NET_CMD_RESIZE_DEVICES,
 	SCOUTFS_NET_CMD_FAREWELL,
 	SCOUTFS_NET_CMD_UNKNOWN,
 };
@@ -1028,6 +1029,11 @@ struct scoutfs_net_roots {
 	struct scoutfs_btree_root srch_root;
 };
 
+struct scoutfs_net_resize_devices {
+	__le64 new_total_meta_blocks;
+	__le64 new_total_data_blocks;
+};
+
 struct scoutfs_net_lock {
 	struct scoutfs_key key;
 	__le64 write_seq;
diff --git a/kmod/src/ioctl.c b/kmod/src/ioctl.c
index cb3f4a4e..59092d89 100644
--- a/kmod/src/ioctl.c
+++ b/kmod/src/ioctl.c
@@ -867,13 +867,21 @@ static long scoutfs_ioc_statfs_more(struct file *file, unsigned long arg)
 {
 	struct super_block *sb = file_inode(file)->i_sb;
 	struct scoutfs_sb_info *sbi = SCOUTFS_SB(sb);
-	struct scoutfs_super_block *super = &sbi->super;
+	struct scoutfs_super_block *super;
 	struct scoutfs_ioctl_statfs_more sfm;
 	int ret;
 
 	if (get_user(sfm.valid_bytes, (__u64 __user *)arg))
 		return -EFAULT;
 
+	super = kzalloc(sizeof(struct scoutfs_super_block), GFP_NOFS);
+	if (!super)
+		return -ENOMEM;
+
+	ret = scoutfs_read_super(sb, super);
+	if (ret)
+		goto out;
+
 	sfm.valid_bytes = min_t(u64, sfm.valid_bytes,
 				sizeof(struct scoutfs_ioctl_statfs_more));
 	sfm.fsid = le64_to_cpu(super->hdr.fsid);
@@ -884,12 +892,15 @@ static long scoutfs_ioc_statfs_more(struct file *file, unsigned long arg)
 
 	ret = scoutfs_client_get_last_seq(sb, &sfm.committed_seq);
 	if (ret)
-		return ret;
+		goto out;
 
 	if (copy_to_user((void __user *)arg, &sfm, sfm.valid_bytes))
-		return -EFAULT;
-
-	return 0;
+		ret = -EFAULT;
+	else
+		ret = 0;
+out:
+	kfree(super);
+	return ret;
 }
 
 struct copy_alloc_detail_args {
@@ -993,6 +1004,37 @@ out:
 	return ret;
 }
 
+static long scoutfs_ioc_resize_devices(struct file *file, unsigned long arg)
+{
+	struct super_block *sb = file_inode(file)->i_sb;
+	struct scoutfs_ioctl_resize_devices __user *urd = (void __user *)arg;
+	struct scoutfs_ioctl_resize_devices rd;
+	struct scoutfs_net_resize_devices nrd;
+	int ret;
+
+	if (!(file->f_mode & FMODE_READ)) {
+		ret = -EBADF;
+		goto out;
+	}
+
+	if (!capable(CAP_SYS_ADMIN)) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	if (copy_from_user(&rd, urd, sizeof(rd))) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	nrd.new_total_meta_blocks = cpu_to_le64(rd.new_total_meta_blocks);
+	nrd.new_total_data_blocks = cpu_to_le64(rd.new_total_data_blocks);
+
+	ret = scoutfs_client_resize_devices(sb, &nrd);
+out:
+	return ret;
+}
+
 long scoutfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	switch (cmd) {
@@ -1022,6 +1064,8 @@ long scoutfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		return scoutfs_ioc_alloc_detail(file, arg);
 	case SCOUTFS_IOC_MOVE_BLOCKS:
 		return scoutfs_ioc_move_blocks(file, arg);
+	case SCOUTFS_IOC_RESIZE_DEVICES:
+		return scoutfs_ioc_resize_devices(file, arg);
 	}
 
 	return -ENOTTY;
diff --git a/kmod/src/ioctl.h b/kmod/src/ioctl.h
index 446611e9..469551d9 100644
--- a/kmod/src/ioctl.h
+++ b/kmod/src/ioctl.h
@@ -477,4 +477,12 @@ struct scoutfs_ioctl_move_blocks {
 #define SCOUTFS_IOC_MOVE_BLOCKS _IOR(SCOUTFS_IOCTL_MAGIC, 13, \
 				     struct scoutfs_ioctl_move_blocks)
 
+struct scoutfs_ioctl_resize_devices {
+	__u64 new_total_meta_blocks;
+	__u64 new_total_data_blocks;
+};
+
+#define SCOUTFS_IOC_RESIZE_DEVICES \
+	_IOR(SCOUTFS_IOCTL_MAGIC, 14, struct scoutfs_ioctl_resize_devices)
+
 #endif
diff --git a/kmod/src/server.c b/kmod/src/server.c
index 93480a36..d605d0ca 100644
--- a/kmod/src/server.c
+++ b/kmod/src/server.c
@@ -2563,6 +2563,103 @@ out:
 	return scoutfs_net_response(sb, conn, cmd, id, ret, NULL, 0);
 }
 
+static u64 device_blocks(struct block_device *bdev, int shift)
+{
+	return i_size_read(bdev->bd_inode) >> shift;
+}
+
+static int server_resize_devices(struct super_block *sb, struct scoutfs_net_connection *conn,
+				 u8 cmd, u64 id, void *arg, u16 arg_len)
+{
+	DECLARE_SERVER_INFO(sb, server);
+	struct scoutfs_sb_info *sbi = SCOUTFS_SB(sb);
+	struct scoutfs_super_block *super = &SCOUTFS_SB(sb)->super;
+	struct scoutfs_net_resize_devices *nrd;
+	u64 meta_tot;
+	u64 meta_start;
+	u64 meta_len;
+	u64 data_tot;
+	u64 data_start;
+	u64 data_len;
+	int ret;
+	int err;
+
+	if (arg_len != sizeof(struct scoutfs_net_resize_devices)) {
+		ret = -EINVAL;
+		goto out;
+	}
+	nrd = arg;
+
+	meta_tot = le64_to_cpu(nrd->new_total_meta_blocks);
+	data_tot = le64_to_cpu(nrd->new_total_data_blocks);
+
+	scoutfs_server_hold_commit(sb);
+	mutex_lock(&server->alloc_mutex);
+
+	if (meta_tot == le64_to_cpu(super->total_meta_blocks))
+		meta_tot = 0;
+	if (data_tot == le64_to_cpu(super->total_data_blocks))
+		data_tot = 0;
+
+	if (!meta_tot && !data_tot) {
+		ret = 0;
+		goto unlock;
+	}
+
+	/* we don't support shrinking */
+	if ((meta_tot && (meta_tot < le64_to_cpu(super->total_meta_blocks))) ||
+	    (data_tot && (data_tot < le64_to_cpu(super->total_data_blocks)))) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	/* must be within devices */
+	if ((meta_tot > device_blocks(sbi->meta_bdev, SCOUTFS_BLOCK_LG_SHIFT)) ||
+	    (data_tot > device_blocks(sb->s_bdev, SCOUTFS_BLOCK_SM_SHIFT))) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	/* extents are only used if _tot is set */
+	meta_start = le64_to_cpu(super->total_meta_blocks);
+	meta_len = meta_tot - meta_start;
+	data_start = le64_to_cpu(super->total_data_blocks);
+	data_len = data_tot - data_start;
+
+	if (meta_tot) {
+		ret = scoutfs_alloc_insert(sb, &server->alloc, &server->wri,
+					   server->meta_avail, meta_start, meta_len);
+		if (ret < 0)
+			goto unlock;
+	}
+
+	if (data_tot) {
+		ret = scoutfs_alloc_insert(sb, &server->alloc, &server->wri,
+					   &super->data_alloc, data_start, data_len);
+		if (ret < 0) {
+			if (meta_tot) {
+				err = scoutfs_alloc_remove(sb, &server->alloc, &server->wri,
+							   server->meta_avail, meta_start,
+							   meta_len);
+				WARN_ON_ONCE(err); /* btree blocks are dirty.. really unlikely? */
+			}
+			goto unlock;
+		}
+	}
+
+	if (meta_tot)
+		super->total_meta_blocks = cpu_to_le64(meta_tot);
+	if (data_tot)
+		super->total_data_blocks = cpu_to_le64(data_tot);
+
+	ret = 0;
+unlock:
+	mutex_unlock(&server->alloc_mutex);
+	ret = scoutfs_server_apply_commit(sb, ret);
+out:
+	return scoutfs_net_response(sb, conn, cmd, id, ret, NULL, 0);
+};
+
 static void init_mounted_client_key(struct scoutfs_key *key, u64 rid)
 {
 	*key = (struct scoutfs_key) {
@@ -3199,6 +3296,7 @@ static scoutfs_net_request_t server_req_funcs[] = {
 	[SCOUTFS_NET_CMD_GET_VOLOPT]		= server_get_volopt,
 	[SCOUTFS_NET_CMD_SET_VOLOPT]		= server_set_volopt,
 	[SCOUTFS_NET_CMD_CLEAR_VOLOPT]		= server_clear_volopt,
+	[SCOUTFS_NET_CMD_RESIZE_DEVICES]	= server_resize_devices,
 	[SCOUTFS_NET_CMD_FAREWELL]		= server_farewell,
 };
 
diff --git a/tests/golden/resize-devices b/tests/golden/resize-devices
new file mode 100644
index 00000000..3b2529fe
--- /dev/null
+++ b/tests/golden/resize-devices
@@ -0,0 +1,27 @@
+== make initial small fs
+== 0s do nothing
+== shrinking fails
+resize_devices ioctl failed: Invalid argument (22)
+scoutfs: resize-devices failed: Invalid argument (22)
+resize_devices ioctl failed: Invalid argument (22)
+scoutfs: resize-devices failed: Invalid argument (22)
+resize_devices ioctl failed: Invalid argument (22)
+scoutfs: resize-devices failed: Invalid argument (22)
+== existing sizes do nothing
+== growing outside device fails
+resize_devices ioctl failed: Invalid argument (22)
+scoutfs: resize-devices failed: Invalid argument (22)
+resize_devices ioctl failed: Invalid argument (22)
+scoutfs: resize-devices failed: Invalid argument (22)
+resize_devices ioctl failed: Invalid argument (22)
+scoutfs: resize-devices failed: Invalid argument (22)
+== resizing meta works
+== resizing data works
+== shrinking back fails
+resize_devices ioctl failed: Invalid argument (22)
+scoutfs: resize-devices failed: Invalid argument (22)
+resize_devices ioctl failed: Invalid argument (22)
+scoutfs: resize-devices failed: Invalid argument (22)
+== resizing again does nothing
+== resizing to full works
+== cleanup extra fs
diff --git a/tests/sequence b/tests/sequence
index b97e4847..17955e28 100644
--- a/tests/sequence
+++ b/tests/sequence
@@ -29,6 +29,7 @@ lock-conflicting-batch-commit.sh
 cross-mount-data-free.sh
 persistent-item-vers.sh
 setup-error-teardown.sh
+resize-devices.sh
 fence-and-reclaim.sh
 orphan-inodes.sh
 mount-unmount-race.sh
diff --git a/tests/tests/resize-devices.sh b/tests/tests/resize-devices.sh
new file mode 100644
index 00000000..9bd91476
--- /dev/null
+++ b/tests/tests/resize-devices.sh
@@ -0,0 +1,149 @@
+#
+# Some basic tests of online resizing metadata and data devices.
+#
+
+statfs_total() {
+	local single="total_$1_blocks"
+	local mnt="$2"
+
+	scoutfs statfs -s $single -p "$mnt"
+}
+
+df_free() {
+	local md="$1"
+	local mnt="$2"
+
+	scoutfs df -p "$mnt" | awk '($1 == "'$md'") { print $5; exit }'
+}
+
+same_totals() {
+	cur_meta_tot=$(statfs_total meta "$SCR")
+	cur_data_tot=$(statfs_total data "$SCR")
+
+	test "$cur_meta_tot" == "$exp_meta_tot" || \
+		t_fail "cur total_meta_blocks $cur_meta_tot != expected $exp_meta_tot"
+	test "$cur_data_tot" == "$exp_data_tot" || \
+		t_fail "cur total_data_blocks $cur_data_tot != expected $exp_data_tot"
+}
+
+#
+# make sure that the specified devices have grown by doubling.   The
+# total blocks can be tested exactly but the df reported total needs
+# some slop to account for reserved blocks and concurrent allocation.
+#
+devices_grew() {
+	cur_meta_tot=$(statfs_total meta "$SCR")
+	cur_data_tot=$(statfs_total data "$SCR")
+	cur_meta_df=$(df_free MetaData "$SCR")
+	cur_data_df=$(df_free Data "$SCR")
+
+	local grow_meta_tot=$(echo "$exp_meta_tot * 2" | bc)
+	local grow_data_tot=$(echo "$exp_data_tot * 2" | bc)
+	local grow_meta_df=$(echo "($exp_meta_df * 1.95)/1" | bc)
+	local grow_data_df=$(echo "($exp_data_df * 1.95)/1" | bc)
+
+	if [ "$1" == "meta" ]; then
+		test "$cur_meta_tot" == "$grow_meta_tot" || \
+			t_fail "cur total_meta_blocks $cur_meta_tot != grown $grow_meta_tot"
+		test "$cur_meta_df" -lt "$grow_meta_df" && \
+			t_fail "cur meta df total $cur_meta_df < grown $grow_meta_df"
+		exp_meta_tot=$cur_meta_tot
+		exp_meta_df=$cur_meta_df
+		shift
+	fi
+
+	if [ "$1" == "data" ]; then
+		test "$cur_data_tot" == "$grow_data_tot" || \
+			t_fail "cur total_data_blocks $cur_data_tot != grown $grow_data_tot"
+		test "$cur_data_df" -lt "$grow_data_df" && \
+			t_fail "cur data df total $cur_data_df < grown $grow_data_df"
+		exp_data_tot=$cur_data_tot
+		exp_data_df=$cur_data_df
+	fi
+}
+
+# first calculate small mkfs based on device size
+size_meta=$(blockdev --getsize64 "$T_EX_META_DEV")
+size_data=$(blockdev --getsize64 "$T_EX_DATA_DEV")
+quarter_meta=$(echo "$size_meta / 4" | bc)
+quarter_data=$(echo "$size_data / 4" | bc)
+
+# XXX this is all pretty manual, would be nice to have helpers
+echo "== make initial small fs"
+scoutfs mkfs -A -f -Q 0,127.0.0.1,53000 -m $quarter_meta -d $quarter_data \
+	"$T_EX_META_DEV" "$T_EX_DATA_DEV" > $T_TMP.mkfs.out 2>&1 || \
+		t_fail "mkfs failed"
+SCR="/mnt/scoutfs.enospc"
+mkdir -p "$SCR"
+mount -t scoutfs -o metadev_path=$T_EX_META_DEV,quorum_slot_nr=0 \
+	"$T_EX_DATA_DEV" "$SCR"
+
+# then calculate sizes based on blocks that mkfs used
+quarter_meta=$(echo "$(statfs_total meta "$SCR") * 64 * 1024" | bc)
+quarter_data=$(echo "$(statfs_total data "$SCR") * 4 * 1024" | bc)
+whole_meta=$(echo "$quarter_meta * 4" | bc)
+whole_data=$(echo "$quarter_data * 4" | bc)
+outsize_meta=$(echo "$whole_meta * 2" | bc)
+outsize_data=$(echo "$whole_data * 2" | bc)
+half_meta=$(echo "$whole_meta / 2" | bc)
+half_data=$(echo "$whole_data / 2" | bc)
+shrink_meta=$(echo "$quarter_meta / 2" | bc)
+shrink_data=$(echo "$quarter_data / 2" | bc)
+
+# and save expected values for checks
+exp_meta_tot=$(statfs_total meta "$SCR")
+exp_meta_df=$(df_free MetaData "$SCR")
+exp_data_tot=$(statfs_total data "$SCR")
+exp_data_df=$(df_free Data "$SCR")
+
+echo "== 0s do nothing"
+scoutfs resize-devices -p "$SCR" 
+scoutfs resize-devices -p "$SCR" -m 0
+scoutfs resize-devices -p "$SCR" -d 0
+scoutfs resize-devices -p "$SCR" -m 0 -d 0
+
+echo "== shrinking fails"
+scoutfs resize-devices -p "$SCR" -m $shrink_meta
+scoutfs resize-devices -p "$SCR" -d $shrink_data
+scoutfs resize-devices -p "$SCR" -m $shrink_meta -d $shrink_data
+same_totals
+
+echo "== existing sizes do nothing"
+scoutfs resize-devices -p "$SCR" -m $quarter_meta
+scoutfs resize-devices -p "$SCR" -d $quarter_data
+scoutfs resize-devices -p "$SCR" -m $quarter_meta -d $quarter_data
+same_totals
+
+echo "== growing outside device fails"
+scoutfs resize-devices -p "$SCR" -m $outsize_meta
+scoutfs resize-devices -p "$SCR" -d $outsize_data
+scoutfs resize-devices -p "$SCR" -m $outsize_meta -d $outsize_data
+same_totals
+
+echo "== resizing meta works"
+scoutfs resize-devices -p "$SCR" -m $half_meta
+devices_grew meta
+
+echo "== resizing data works"
+scoutfs resize-devices -p "$SCR" -d $half_data
+devices_grew data
+
+echo "== shrinking back fails"
+scoutfs resize-devices -p "$SCR" -m $quarter_meta
+scoutfs resize-devices -p "$SCR" -m $quarter_data
+same_totals
+
+echo "== resizing again does nothing"
+scoutfs resize-devices -p "$SCR" -m $half_meta
+scoutfs resize-devices -p "$SCR" -m $half_data
+same_totals
+
+echo "== resizing to full works"
+scoutfs resize-devices -p "$SCR" -m $whole_meta -d $whole_data
+devices_grew meta data
+
+echo "== cleanup extra fs"
+umount "$SCR"
+rmdir "$SCR"
+
+t_pass
diff --git a/utils/man/scoutfs.8 b/utils/man/scoutfs.8
index d7723302..25ee53c7 100644
--- a/utils/man/scoutfs.8
+++ b/utils/man/scoutfs.8
@@ -103,6 +103,63 @@ Ignore presence of existing data on the data and metadata devices.
 .PD
 
 .TP
+.BI "resize-devices [-p|--path PATH] [-m|--meta-size SIZE] [-d|--data-size SIZE]"
+.sp
+Resize the metadata or data devices of a mounted ScoutFS filesystem.
+.sp
+ScoutFS metadata has free extent records and fields in the super block
+that reflect the size of the devices in use.  This command sends a
+request to the server to change the size of the device that can be used
+by updating free extents and setting the super block fields.
+.sp
+The specified sizes are in bytes and are translated into block counts.
+If the specified sizes are not a multiple of the metadata or data block
+sizes then a message is output and the resized size is truncated down to
+the next whole block.  Specifying either a size of 0 or the current
+device size makes no change.    The current size of the devices can be
+seen, in units of their respective block sizes, in the total_meta_blocks
+and total_data_blocks fields returned by the scoutfs statfs command (via
+the statfs_more ioctl).
+.sp
+Shrinking is not supported.  Specifying a smaller size for either device
+will return an error and neither device will be resized.
+.sp
+Specifying a larger size will expand the initial size of the device that
+will be used.  Free space records are added for the expanded region and
+can be used once the resizing transaction is complete.
+.sp
+The resizing action is performed in a transaction on the server.  This
+command will hang until a server is elected and running and can service
+the reqeust.  The server serializes any concurrent requests to resize.
+.sp
+The new sizes must fit within the current sizes of the mounted devices.
+Presumably this command is being performed as part of a larger
+coordinated resize of the underlying devices.  The device must be
+expanded before ScoutFS can use the larger device and ScoutFS must stop
+using a region to shrink before it could be removed from the device
+(which is not currently supported).
+.sp
+The resize will be committed by the server before the response is sent
+to the client.  The system can be using the new device size before the
+result is communicated through the client and this command completes.
+The client could crash and the server could still have performed the
+resize.
+.RS 1.0i
+.PD 0
+.TP
+.sp
+.B "-p, --path PATH"
+A path in the mounted ScoutFS filesystem which will have its devices
+resized.
+.TP
+.B "-m, --meta-size SIZE"
+.B "-d, --data-size SIZE"
+The new size of the metadata or data device to use, in bytes.  Size is given as
+an integer followed by a units digit: "K", "M", "G", "T", "P", to denote
+kibibytes, mebibytes, etc.
+.RE
+.PD
+
 .BI "stat FILE [-s|--single-field FIELD-NAME]"
 .sp
 Display ScoutFS-specific metadata fields for the given file.
diff --git a/utils/src/resize_devices.c b/utils/src/resize_devices.c
new file mode 100644
index 00000000..bdf6659b
--- /dev/null
+++ b/utils/src/resize_devices.c
@@ -0,0 +1,120 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <argp.h>
+
+#include "sparse.h"
+#include "parse.h"
+#include "util.h"
+#include "format.h"
+#include "ioctl.h"
+#include "cmd.h"
+
+struct resize_args {
+	char *path;
+	u64 meta_size;
+	u64 data_size;
+};
+
+static int do_resize_devices(struct resize_args *args)
+{
+	struct scoutfs_ioctl_resize_devices rd;
+	int ret;
+	int fd;
+
+	if (args->meta_size & SCOUTFS_BLOCK_LG_MASK) {
+		printf("metadata device size %llu is not a multiple of %u metadata block size, truncating down to %llu byte size\n",
+		args->meta_size, SCOUTFS_BLOCK_LG_SIZE,
+		args->meta_size & ~(u64)SCOUTFS_BLOCK_LG_MASK);
+	}
+
+	if (args->data_size & SCOUTFS_BLOCK_SM_MASK) {
+		printf("data device size %llu is not a multiple of %u data block size, truncating down to %llu byte size\n",
+		args->data_size, SCOUTFS_BLOCK_SM_SIZE,
+		args->data_size & ~(u64)SCOUTFS_BLOCK_SM_MASK);
+	}
+
+	fd = get_path(args->path, O_RDONLY);
+	if (fd < 0)
+		return fd;
+
+	rd.new_total_meta_blocks = args->meta_size >> SCOUTFS_BLOCK_LG_SHIFT;
+	rd.new_total_data_blocks = args->data_size >> SCOUTFS_BLOCK_SM_SHIFT;
+
+	ret = ioctl(fd, SCOUTFS_IOC_RESIZE_DEVICES, &rd);
+	if (ret < 0) {
+		ret = -errno;
+		fprintf(stderr, "resize_devices ioctl failed: %s (%d)\n", strerror(errno), errno);
+	}
+
+	close(fd);
+	return ret;
+};
+
+static int parse_opt(int key, char *arg, struct argp_state *state)
+{
+	struct resize_args *args = state->input;
+	int ret;
+
+	switch (key) {
+	case 'm': /* meta-size */
+	{
+		ret = parse_human(arg, &args->meta_size);
+		if (ret)
+			return ret;
+		break;
+	}
+	case 'd': /* data-size */
+	{
+		ret = parse_human(arg, &args->data_size);
+		if (ret)
+			return ret;
+		break;
+	}
+	case 'p':
+		args->path = strdup_or_error(state, arg);
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+static struct argp_option options[] = {
+	{ "path", 'p', "PATH", 0, "Path to ScoutFS filesystem"},
+	{ "meta-size", 'm', "SIZE", 0, "New metadata device size (bytes or KMGTP units)"},
+	{ "data-size", 'd', "SIZE", 0, "New data device size (bytes or KMGTP units)"},
+	{ NULL }
+};
+
+static struct argp argp = {
+	options,
+	parse_opt,
+	"",
+	"Online resize of metadata and/or data devices",
+};
+
+static int resize_devices_cmd(int argc, char **argv)
+{
+
+	struct resize_args resize_args = {NULL,};
+	int ret;
+
+	ret = argp_parse(&argp, argc, argv, 0, NULL, &resize_args);
+	if (ret)
+		return ret;
+
+	return do_resize_devices(&resize_args);
+}
+
+static void __attribute__((constructor)) read_xattr_totals_ctor(void)
+{
+	cmd_register_argp("resize-devices", &argp, GROUP_CORE, resize_devices_cmd);
+}