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<h2 id="history">History</h2> <p>During the 2.5 development cycle, the Linux driver model was introduced to fix the following shortcomings of version 2.4: </p> <ul><li>No unified method of representing driver-device relationships existed.</li> <li>There was no generic <a href="/facts/Hot_swapping/Jn56Jw3h">hotplug</a> mechanism.</li> <li><a href="/facts/Procfs/qGd3Ncgz">procfs</a> was cluttered with non-process information.</li></ul> <p>Sysfs was designed to export the information present in the <a href="/facts/Device_tree/Lw84twBP">device tree</a> which would then no longer clutter up procfs. It was written by Patrick Mochel.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Maneesh Soni later wrote the sysfs backing store patch to reduce memory usage on large systems. </p><p>During the next year of 2.5 development the infrastructural capabilities of the driver model and driverfs began to prove useful to other subsystems.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> kobjects were developed to provide a central object management mechanism and driverfs was renamed to sysfs to represent its subsystem agnosticism. </p><p>Sysfs is mounted under the /sys mount point. If it is not mounted automatically during initialization, it can be mounted manually using the <a href="/facts/Mount_(Unix)/VlDPf1Hm">mount</a> command: mount -t sysfs sysfs /sys.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h2 id="supported-buses">Supported buses</h2> ACPI Exports information about <a href="/facts/Advanced_Configuration_and_Power_Interface/GnLLzfyr">ACPI</a> devices. PCI Exports information about <a href="/facts/Peripheral_Component_Interconnect/n6CGuFvP">PCI</a> and <a href="/facts/PCI_Express/ADhsLCUK">PCI Express</a> devices. PCI Express Exports information about <a href="/facts/PCI_Express/ADhsLCUK">PCI Express</a> devices. USB Exports information about <a href="/facts/Universal_Serial_Bus/XcIKWLyg">USB</a> devices. SCSI Exports information about <a href="/facts/Mass_storage/p4DHVtbY">mass storage</a> devices, including <a href="/facts/USB/XcIKWLyg">USB</a>, <a href="/facts/Serial_ATA/dW8yAMm8">SATA</a> and <a href="/facts/NVMe/Ye7N4elE">NVMe</a> interfaces.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> S/390 buses As the <a href="/facts/S%2f390/lzkp2UE5">S/390</a> architecture contains devices not found elsewhere, special buses have been created: <ul><li><i>css</i>: Contains subchannels (currently the only driver provided is for I/O subchannels).</li> <li><i>ccw</i>: Contains channel attached devices (driven by <a href="/facts/Channel_command_word/vDBtN2wQ">CCWs</a>).</li> <li><i>ccwgroup</i>: Artificial devices, created by the user and consisting of ccw devices. Replaces some of the 2.4 chandev functionality.</li> <li><i>iucv</i>: Artificial devices like netiucv devices which use VM's <a href="/facts/IUCV/4y0pdR7m">IUCV</a> interface.</li></ul> <h2 id="sysfs-and-userspace">Sysfs and userspace</h2> <p>Sysfs is used by several utilities to access information about hardware and its driver (<a href="/facts/Module_(Linux)/UXvHsj2c">kernel modules</a>) such as <a href="/facts/Udev/89smRMUF">udev</a> or <a href="/facts/HAL_(software)/GkBMPdPL">HAL</a>. Scripts have been written to access information previously obtained via <a href="/facts/Procfs/qGd3Ncgz">procfs</a>, and some scripts configure device drivers and devices via their attributes. </p> <h2 id="see-also">See also</h2> <ul> <li>Linux portal</li></ul> <ul><li><a href="/facts/Procfs/qGd3Ncgz">procfs</a></li> <li><a href="/facts/Configfs/CQGFTKc6">configfs</a></li> <li><a href="/facts/Tmpfs/7WM9xAbs">tmpfs</a></li> <li><a href="/facts/Sysctl/dNkty2DA">sysctl</a>, alternative way of exporting configuration used in BSD systems</li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://lwn.net/Articles/31185/">Driver model overview from the LWN porting to 2.6 series</a></li> <li><a href="https://lwn.net/Articles/54651/">kobjects and sysfs from the LWN porting to 2.6 series</a></li> <li><a href="http://wiki.debian.org/ramfs">Ramfs</a></li> <li><a href="https://www.kernel.org/pub/linux/kernel/people/mochel/doc/papers/ols-2005/mochel.pdf">The sysfs Filesystem, OLS'05</a></li> <li><a href="http://kernel.org/doc/Documentation/filesystems/sysfs.txt">Documentation/filesystems/sysfs.txt</a> Linux kernel documentation for sysfs</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Patrick Mochel and Mike Murphy. "sysfs - _The_ filesystem for exporting kernel objects". kernel.org. <a href="https://www.kernel.org/doc/Documentation/filesystems/sysfs.txt" target="_blank">https://www.kernel.org/doc/Documentation/filesystems/sysfs.txt</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>SUSE. "sysctl man page". FreeBSD. sysctl is used to modify kernel parameters at runtime. The parameters available are those listed under /proc/sys/. Procfs is required for sysctl support in Linux. You can use sysctl to both read and write sysctl data. <a href="https://www.freebsd.org/cgi/man.cgi?query=sysctl&sektion=8&manpath=SuSE+Linux%2fi386+11.3" target="_blank">https://www.freebsd.org/cgi/man.cgi?query=sysctl&sektion=8&manpath=SuSE+Linux%2fi386+11.3</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Torvalds, Linus (18 October 2002). "Linux v2.5.44 - and offline for a week". <a href="https://lkml.org/lkml/2002/10/19/8" target="_blank">https://lkml.org/lkml/2002/10/19/8</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Torvalds, Linus (4 November 2002). "Linux v2.5.46". <a href="https://lkml.org/lkml/2002/11/4/213" target="_blank">https://lkml.org/lkml/2002/11/4/213</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Mochel, Patrick (17 October 2001). "[RFC] New Driver Model for 2.5". <a href="https://lkml.org/lkml/2001/10/17/147" target="_blank">https://lkml.org/lkml/2001/10/17/147</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Jansen, Tim (1 November 2001). "Re: [PATCH] 2.5 PROPOSAL: Replacement for current /proc of shit". <a href="https://lkml.org/lkml/2001/11/1/38" target="_blank">https://lkml.org/lkml/2001/11/1/38</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Patrick Mochel and Mike Murphy. "sysfs - _The_ filesystem for exporting kernel objects". kernel.org. <a href="https://www.kernel.org/doc/Documentation/filesystems/sysfs.txt" target="_blank">https://www.kernel.org/doc/Documentation/filesystems/sysfs.txt</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"SCSI Interfaces Guide — The Linux Kernel documentation". www.kernel.org. Retrieved 2020-11-13. <a href="https://www.kernel.org/doc/html/latest/driver-api/scsi.html" target="_blank">https://www.kernel.org/doc/html/latest/driver-api/scsi.html</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> </ol>