---
name: "nfsdtop"
section: "8"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/nfsdtop"
---

# nfsdtop(8)

display top-like NFS server I/O statistics

## NAME

**nfsdtop** – display top-like NFS server I/O statistics

## SYNOPSIS

**nfsdtop** \[**-aDdhnoqRrvw**\] \[**-b** \| **-j** \| **-J**\] \[**-C** *ip*\] \[**-c** \| **-g** \| **-u**\] \[**-G** *group*\] \[**-I** *file*\] \[**-i** *sec*\] \[**-N** *num*\] \[**-P** *file*\] \[**-p** *file*\] \[**-U** *user*\]

## DESCRIPTION

The **nfsdtop** utility uses [dtrace(1)](/dtrace/1.md) to display a periodically updated table of NFS server read and write activity. Statistics are taken from the [nfsd(8)](/nfsd/8.md) read and write paths (**nfsrvd\_read**(*,*, *Fn*, *nfsvno\_read*, *,*, *Fn*, *nfsrvd\_write*, *,*, *and*, *Fn*, *nfsvno\_write*)) and coalesced by a chosen *view*.

Only the root user or users with [dtrace(1)](/dtrace/1.md) privileges can run this command.

A view selects the first column of the display. The default is the user view (‘**-u**’), where each row is a UID (or user name). The group view (‘**-g**’) and client view (‘**-c**’) instead coalesce by GID or IPv4 client address. Without ‘**-j**’, the last of ‘**-c**’, ‘**-g**’, or ‘**-u**’ wins.

UIDs, GIDs, and IPv4 addresses shown in a view are taken from NFS client credentials and addresses on the [nfsd(8)](/nfsd/8.md) paths. They often cannot be resolved on the nfsd host, so **nfsdtop** does not use [getent(1)](/getent/1.md) to name them as traffic is sampled; that lookup would likely be useless. The map files described in FILES supply those names. Command-line filters are different. A name given to ‘**-U**’, ‘**-G**’, or ‘**-C**’ is resolved once, first from the same map files and then via [getent(1)](/getent/1.md) or [host(1)](/host/1.md), so the resulting UID, GID, or address can be compiled into the [dtrace(1)](/dtrace/1.md) predicates.

Each interval prints a header followed by a ‘total’ row and per-key rows sorted by combined read and write volume. Columns are the view key, combined TOTAL, WRITE(IN), an optional bar, and READ(OUT). Values are humanized bandwidth (bytes per second) unless ‘**-b**’ is given. When standard output is a terminal, the screen is redrawn in place and SIGWINCH resizes the layout.

## OPTIONS

- **-a**

  Always enable color, even when standard output is not a terminal.

- **-b**

  Show bytes transferred during the interval instead of bandwidth. Cannot be combined with ‘**-j**’ or ‘**-J**’.

- **-C** *ip*

  Client filter. Only count I/O for the given IPv4 address or hostname (IPv4 only). A hostname given here is resolved once from the IP map (see **-I**) or [host(1)](/host/1.md).

- **-c**

  View read/write activity by client.

- **-D**

  Enable debugger. Print raw [dtrace(1)](/dtrace/1.md) output and additional post-processor diagnostics.

- **-d**

  Debug. Print the generated [dtrace(1)](/dtrace/1.md) script to standard output and exit.

- **-G** *group*

  Group filter. Only count I/O for the given group name or GID. A name given here is resolved once from the group map (see **-P**) or [getent(1)](/getent/1.md).

- **-g**

  View read/write activity by group.

- **-h**

  Print usage statement and exit.

- **-I** *file*

  IP map file for naming observed client addresses (see DESCRIPTION). Default *.nfsd.hosts* in the current directory. Each non-comment line is an IPv4 address followed by a hostname.

- **-i** *sec*

  Set interval seconds. Default ‘2.0’. Must be at least 0.001.

- **-J**

  Output JSON for the client, group, and user views. Same as ‘**-jcgu**’.

- **-j**

  Output JSON formatted data. Each interval emits one object for the view total and one object per key. Objects contain time, ident, total\_bytes, total\_rate, read\_bytes, read\_rate, write\_bytes, and write\_rate.

- **-N** *num*

  Perform *num* samples and exit.

- **-n**

  Do not map observed UIDs, GIDs, or IPs through the map files.

- **-o**

  Force non-console output. Disable screen redraw and color.

- **-P** *file*

  Group map file for naming observed GIDs (see DESCRIPTION). Default *.nfsd.group* in the current directory. Format is [group(5)](/group/5.md).

- **-p** *file*

  User map file for naming observed UIDs (see DESCRIPTION). Default *.nfsd.passwd* in the current directory. Format is [passwd(5)](/passwd/5.md).

- **-q**

  Quiet. Hide informational messages.

- **-R**

  Redact potentially sensitive information. User, group, and client names that are not well-known system accounts are replaced with random strings of the same length. May also be enabled by setting NFSDTOP\_REDACT in the environment.

- **-r**

  Raw view. Do not format output of [dtrace(1)](/dtrace/1.md).

- **-U** *user*

  User filter. Only count I/O for the given user name or UID. A name given here is resolved once from the user map (see **-p**) or [getent(1)](/getent/1.md).

- **-u**

  View read/write activity by user (default).

- **-v**

  Print version and exit.

- **-w**

  Wide view. Maximize width of the first column.

## ENVIRONMENT

- NFSDTOP\_REDACT

  If set to a non-empty value, enable redaction as with ‘**-R**’.

## FILES

These files map identifiers from observed NFS traffic to names. [getent(1)](/getent/1.md) on the nfsd host is not used for that translation.

- *.nfsd.passwd*

  Default user map (‘**-p**’), looked up in the current directory.

- *.nfsd.group*

  Default group map (‘**-P**’), looked up in the current directory.

- *.nfsd.hosts*

  Default IP map (‘**-I**’), looked up in the current directory.

## EXIT STATUS

The **nfsdtop** utility exits 0 on success, and \>0 if an error occurs.

## EXAMPLES

Display per-user NFS server I/O, updated every two seconds:

```
nfsdtop
```

View activity by NFS client:

```
nfsdtop -c
```

Restrict the group view to ‘wheel’:

```
nfsdtop -g -G wheel
```

Count only I/O from one client and show bytes instead of bandwidth:

```
nfsdtop -c -C 192.0.2.10 -b
```

Emit one JSON sample for all views and exit:

```
nfsdtop -J -N 1
```

Print the generated DTrace script without running it:

```
nfsdtop -d
```

## SEE ALSO

[dtrace(1)](/dtrace/1.md), [dwatch(1)](/dwatch/1.md), [getent(1)](/getent/1.md), [nfsstat(1)](/nfsstat/1.md), [group(5)](/group/5.md), [passwd(5)](/passwd/5.md), [gstat(8)](/gstat/8.md), [iostat(8)](/iostat/8.md), [nfsd(8)](/nfsd/8.md)

## HISTORY

The **nfsdtop** utility first appeared in FreeBSD 16.0.

## AUTHORS

Devin Teske ⟨*dteske@FreeBSD.org*⟩

## BUGS

The client view and ‘**-C**’ filter support IPv4 only.