---
name: "iser"
section: "4"
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/iser"
---

# iser(4)

iSCSI Extensions for RDMA (iSER) driver

## NAME

**iser** – iSCSI Extensions for RDMA (iSER) driver

## SYNOPSIS

To compile this driver into the kernel, place the following line in the kernel configuration file:

**device iser**

Alternatively, to load the driver as a module at boot time, place the following line in [loader.conf(5)](/loader.conf/5.md):

```
iser_load="YES"
```

## DESCRIPTION

The **iser** (iSCSI Extensions for RDMA) initiator driver extends the iSCSI protocol to RDMA. It permits data to be transferred directly into and out of SCSI buffers without intermediate data copies. iSER uses the RDMA protocol suite to supply higher bandwidth for block storage transfers (zero copy behavior). To that fact, it eliminates the TCP/IP processing overhead while preserving the compatibility with iSCSI protocol. The initiator is the iSCSI/iSER client, which connects to an iSCSI/iSER target, providing local access to a remote block device. The userland component is provided by [iscsid(8)](/iscsid/8.md) and both the kernel and userland are configured using [iscsictl(8)](/iscsictl/8.md).

## SYSCTL VARIABLES

The following variables are available as both [sysctl(8)](/sysctl/8.md) variables and [loader(8)](/loader/8.md) tunables:

- *kern.iser.debug*

  Verbosity level for log messages from the **iser** driver. Set to 0 to disable logging or 1 to warn about potential problems. Larger values enable info and debugging output. Defaults to 0.

## SEE ALSO

[iscsi(4)](/iscsi/4.md), [iscsi.conf(5)](/iscsi.conf/5.md), [iscsictl(8)](/iscsictl/8.md), [iscsid(8)](/iscsid/8.md)

## HISTORY

The **iser** subsystem first appeared in FreeBSD 11.0.

## AUTHORS

The **iser** subsystem was developed by Max Gurtovoy ⟨*maxg@mellanox.com*⟩ and Sagi Grimberg ⟨*sagig@mellanox.com*⟩ under sponsorship from Mellanox Technologies.