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Libiscsi is a client-side library to implement the iSCSI protocol that can be used to access the resources of an iSCSI target.

The library is fully asynchronous with regards to iSCSI commands and SCSI tasks, but a synchronous layer is also provided for ease of use for simpler applications.

The utils directory contains a handful of useful iSCSI utilities such as logging in to and enumerating all targets on a portal and all devices of a target.

The examples directory contains example implementation of how to access both the synchronous and asynchronous APIs of libiscsi.

The test-tool directory contains an iSCSI conformance test suite.

Libiscsi is a work in progress. It aims to become a fully asynchronous library for iSCSI functionality, including all features required to establish and maintain an iSCSI session, as well as a low-level SCSI library to create SCSI CDBs and parse/unmarshall data-in structures.


./ ./configure make sudo make install

Build RPM

To build RPMs run the following script from the libiscsi root directory ./packaging/RPM/

iSCSI URL Format

iSCSI devices are specified by a URL format of the following form : iscsi://[[%]@][:]//[?[&]] or iser://[[%]@][:]//[?[&]]

Arguments: Username and password for bidirectional CHAP authentication: target_user= target_password= header_digest=<crc32c|none> Transport: iser

Example: iscsi://server/iqn.ronnie.test/1

CHAP Authentication

CHAP authentication can be specified two ways. Either via the URL itself or through environment variables.

Note that when setting it via the URL, be careful so that username/password will not be visible in logfiles or the process list.


CHAP authentication via URL is specified by providing %@ in the server part of the URL:

Example: iscsi://ronnie%password@server/iqn.ronnie.test/1

Environment variables

Setting the CHAP authentication via environment variables: LIBISCSI_CHAP_USERNAME=ronnie LIBISCSI_CHAP_PASSWORD=password

Example: LIBISCSI_CHAP_PASSWORD=password iscsi-inq iscsi://ronnie@

Bidirectional CHAP Authentication

Bidirectional CHAP is when you not only authenticate the initiator to the target but also authenticate the target back to the initiator. This is only available if you also first specify normal authentication as per the previous section.

Bidirectional CHAP can be set either via URL arguments or via environment variables. If specifying it via URL arguments, be careful so that you do not leak the username/password via logfiles or the process list or similar.


URL arguments contain the '&' character so make sure to escape them properly if you pass them in via a commandline.

Example: iscsi://

Environment variables

Setting the CHAP authentication via environment variables: LIBISCSI_CHAP_TARGET_USERNAME=target LIBISCSI_CHAP_TARGET_PASSWORD=password

IPv6 support

Libiscsi supports IPv6, either as names resolving into IPv6 addresses or when IPv6 addresses are explicitely set in the URL. When specifying IPv6 addresses in the URL, they have to be specified in [...] bracket form.

Example: iscsi://[fec0:2727::3]:3260/iqn.ronnie.test/1

Header Digest

Libiscsi supports HeaderDigest. By default, libiscsi will offer None,CRC32C and let the target pick whether Header digest is to be used or not. This can be overridden by an application by calling iscsi_set_header_digest() if the application wants to force a specific setting.


The patches subdirectory contains patches to make some external packages iSCSI-aware and make them use libiscsi. Currently we have SG3-UTILS and MTX. Patches for other packages would be welcome.


iscsi-test-cu is a CUnit based test tool for scsi and iscsi.

iscsi-test-cu depends on the CUnit library and will only build if libcunit can be found during configure.

The configure script will check if a suitable libcunit is available and only build the test tool if it can find libcunit. This test is done toward the end of the configure phase and should result in a line similar to :

checking whether libcunit is available... yes

Test family/suite/test

Tests are divided up in families, suites and tests and are specified as --test=..

A is a logical collection of test suites to cover a broad set of functionality. Example families are 'SCSI' for performing all tests for SCSI commands and 'iSCSI' that contain tests for the iSCSI layer.

To run all tests in the SCSI family you can just specify --test=SCSI or --test=SCSI..

The next layer of tests are the suites. Within a family there are a collection of suites that perform test to cover a specific area of functionality. For example, to run all SCSI tests that cover the Read10 opcode you would specify it as --test=SCSI.Read10 or --test=SCSI.Read10.*

Finally at the lowest level you have the individual tests. These tests perform specific topic in a suite. For example, we have tests for the Read10 opcode that verifies that the target implements the DPO/FUA flags properly. To run those tests you would specify --test=SCSI.Read10.DpoFua

Test discovery

To discover which tests exist you can use the command iscsi-test-cu --list


Run the DpoFua test for Read10 iscsi-test-cu --test=SCSI.Read10.DpoFua iscsi://

Run all Read10 tests iscsi-test-cu --test=SCSI.Read10 iscsi://

Run all SCSI tests for all opcodes iscsi-test-cu --test=SCSI iscsi://

Initiator names used by the test suite

Most tests only require a single login to the target, but some tests, for example the it nexus loss tests may need to login two separate sessions. By default the initiator names use for the logins will be ""; for the primary connection for all tests, and "" for the secondary connection for the test that needs two sessions. These names can be controlled by using the arguments --initiator-name and --initiator-name-2

The tests are all self-documented to describe what they test and how they test. Use -V with a test to print the documentation for a test.


iscsi-test-cu can produce machine-readable test results for consumption by your CI server. Use the --xml option with any test suite(s), and a file called CUnitAutomated-Results.xml will be written to your current working directory. These results can be converted to JUnit format using this script:

See also:



Linux SG_IO devices

When used on Linux, the test tool also supports talking directly to local SG_IO devices. Accessing SG_IO devices often require that you are root:

sudo iscsi-test-cu --test LINUX.Read10.Simple /dev/sg1

Unit Tests

The tests directory contains test scripts and programs to verify the functionality of libiscsi itself. These tests require that you have STGT version 1.0.58 or later installed to use as a taget to test against. To run the tests: cd tests make test


libiscsi is pure POSIX and should with some tweaks run on any host that provides a POSIX-like environment.

Libiscsi has been tested on:

  • Linux (32 and 64 bit)
  • Cygwin
  • FreeBSD
  • Windows (Win7-VisualStudio10)
  • OpenSolaris
  • Solaris 11 : Use "gmake" to build.
  • OS X


Release tarballs are available at


If you want to contribute, please do. For sending me patches you can either do that by sending a pull request to my github repo or you can send them in an email directly to me at


A libiscsi mailing list is available at Announcements of new versions of libiscsi will be posted to this list.


iscsi client library and utilities




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