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Introduction

The Linux target framework (tgt) is a user space SCSI target framework that supports the iSCSI and iSER transport protocols and that supports multiple methods for accessing block storage. Tgt consists of user-space daemon and tools.

Currently, tgt supports the following SCSI transport protocols:

• iSCSI software target driver for Ethernet NICs
• iSER software target driver for Infiniband and RDMA NICs

Tgt supports the following methods for accessing local storage:

• aio, the asynchronous I/O interface also known as libaio.
• rdwr, smc and mmc, synchronous I/O based on the pread() and pwrite() system calls.
• null, discards all data and reads zeroes.
• ssc, SCSI tape support.
• sg and bsg, SCSI pass-through.
• glfs, the GlusterFS network filesystem.
• rbd, Ceph's distributed-storage RADOS Block Device.
• sheepdog, a distributed object storage system.

Tgt can emulate the following SCSI device types:

• SBC: a virtual disk drive that can use a file to store the content.
• SMC: a virtual media jukebox that can be controlled by the "mtx" tool.
• MMC: a virtual DVD drive that can read DVD-ROM iso files and create burnable DVD+R. It can be combined with SMC to provide a fully operational DVD jukebox.
• SSC: a virtual tape device (aka VTL) that can use a file to store the content.
• OSD: a virtual object-based storage device that can use a file to store the content (in progress).

License

The code is released under the GNU General Public License version 2.

Requirements

Target drivers have their own ways to build, configure, etc. Please find an appropriate documentation in the doc directory.

Developer Notes

The central communication channel for tgt development is the mailing list (stgt@vger.kernel.org).

First, please read the following documents (in short, follow Linux kernel development rules):

• https://www.kernel.org/doc/Documentation/process/coding-style.rst
• https://www.kernel.org/doc/Documentation/process/submitting-patches.rst

Then, check your patches with the patch style checker prior to submission (scripts/checkpatch.pl) like the following example.

fujita@arbre:~/git/tgt$ ./scripts/checkpatch.pl ~/0001-add-bidi-support.patch Your patch has no obvious style problems and is ready for submission.