MAKEDEVSection: Linux Programmer's Manual (8)
Updated: 26 June 2001
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NAMEMAKEDEV - create devices
/sbin/MAKEDEV [ -d directory ] [ -D directory ] [ -c configdir ] [ -m maxdevices ] [-a] [-n] [-v] [-i] [-M] [-S] [-u] [-x] device ...
DESCRIPTIONMAKEDEV is a program that will create the devices in /dev used to interface with drivers in the kernel.
Note that programs giving the error ``ENOENT: No such file or directory'' normally means that the device file is missing, whereas ``ENODEV: No such device'' normally means the kernel does not have the driver configured or loaded.
- Print out version and exit.
- Always create devices, even if they already exist and have the proper permissions and file context. The default behavior is to only (re-)create device nodes which appear to be missing or whose permissions differ from the configured values.
- -m maxdevices
- Create no more than the specified number of devices for any specification in a configuration file.
- Do not actually update the devices, just print the actions that would be performed.
- Create symlinks, directories, and sockets belonging to the current user, and print out the list of devices which would be created in a format which is understood by RPM.
- Do not actually update the devices, just print the actions that would be performed in a format which can be fed to a shell.
- -d directory
- Create the devices under directory instead of the default (usually /dev).
- -D directory
- Compute file contexts for device creation as if the directory specified for the -d flag were the specified directory. This is useful if the -d flag is being used to populate a chrooted device directory.
- Print the ownership and permissions for devices instead of creating them. The information is formatted for use by udev.
- Create exactly the named device. By default, device names which have the specified device name as the initial portion of their name are also created. For example, specifying "tty" will also trigger the creation of "tty1", "tty2", and so on.
- Be verbose. Print out the actions as they are performed. This is the same output as produced by the -n option.
- Ignore errors parsing configuration files. .SHCUSTOMIZATION Since there is currently no standardization in what names are used for system users and groups, it is possible that you may need to modify MAKEDEV's configuration files to reflect your site's settings.
- Certain devices are required for minimal functionality. These are:
- mem - access to physical memory; null - null device (infinite sink); port - access to I/O ports; zero - null byte source (infinite source); core - symlink to /proc/kcore (for kernel debugging); full - always returns ENOSPACE on write; ram - ramdisk; tty - to access the controlling tty of a process.
- Virtual Terminals
- This creates the devices associated with the console. These are the virtual terminals ttyx, where x can be from 0 though 63. The device tty0 is the currently active VT, and is also known as console. For each VT, there are two devices: vcsx and vcsax, which can be used to generate screen-dumps of the VT (vcsx is just the text, and vcsax includes the attributes).
- Serial Devices
- Serial ports.
- Pseudo Terminals
- Each possible argument will create a bank of 16 master and slave pairs. The current kernel (1.2) is limited to 64 such pairs. The master pseudo-terminals are pty[p-s][0-9a-f], and the slaves are tty[p-s][0-9a-f].
- Parallel Ports
- Standard parallel ports. The devices are created lp0, lp1, and lp2.
- Bus Mice
- The various bus mice devices. This creates the following devices: logimouse (Logitech bus mouse), psmouse (PS/2-style mouse), msmouse (Microsoft Inport bus mouse) and atimouse (ATI XL bus mouse) and jmouse (J-mouse).
- Joystick Devices
- Joystick. Creates js0 and js1.
- Disk Devices
- Floppy disk devices. The device fdx is the device which autodetects the format, and the additional devices are fixed format (whose size is indicated in the name). The other devices are named as fdxLn. The single letter L identifies the type of floppy disk (d = 5.25" DD, h = 5.25" HD, D = 3.5" DD, H = 3.5" HD, E = 3.5" ED). The number n represents the capacity of that format in K. Thus the standard formats are fdxd360, fdxh1200, fdxD720, fdxH1440, and fdxE2880.
- For more information see Alain Knaff's fdutils package.
- Devices fd0* through fd3* are floppy disks on the first controller, and devices fd4* through fd7* are floppy disks on the second controller.
- AT hard disks. The device hdx provides access to the whole disk, with the partitions being hdx[0-20]. The four primary partitions are hdx1 through hdx4, with the logical partitions being numbered from hdx5 though hdx20. (A primary partition can be made into an extended partition, which can hold 4 logical partitions). By default, only the devices for 4 logical partitions are made. The others can be made by uncommenting them.
- Drives hda and hdb are the two on the first controller. If using the new IDE driver (rather than the old HD driver), then hdc and hdd are the two drives on the secondary controller. These devices can also be used to acess IDE CDROMs if using the new IDE driver.
- XT hard disks. Partitions are the same as IDE disks.
- sd[a-z], sd[a-c][a-z], sdd[a-x]
- SCSI hard disks. The partitions are similar to the IDE disks, but there is a limit of 11 logical partitions (sdx5 through sdx15). This is to allow there to be 128 SCSI disks.
- Loopback disk devices. These allow you to use a regular file as a block device. This means that images of filesystems can be mounted, and used as normal. This creates 16 devices loop0 through loop15.
- Tape Devices
- SCSI tapes. This creates the rewinding tape device stx and the non-rewinding tape device nstx.
- QIC-80 tapes. The devices created are rmt8, rmt16, tape-d, and tape-reset.
- Floppy driver tapes (QIC-117). There are 4 methods of access depending on the floppy tape drive. For each of access methods 0, 1, 2 and 3, the devices rftx (rewinding) and nrftx (non-rewinding) are created. For compatability, devices ftape and nftape are symlinks to rft0 and nrft0 respectively.
- CDROM Devices
- SCSI CD players.
- Sony CDU-31A CD player.
- Mitsumi CD player.
- Sony CDU-535 CD player.
- LMS/Philips CD player.
- Sound Blaster CD player. The kernel is capable of supporting 16 CDROMs, each of which is accessed as sbpcd[0-9a-f]. These are assigned in groups of 4 to each controller. sbpcd is a symlink to sbpcd0.
- Logitech ScanMan32 & ScanMan 256.
- Mustek M105 Handscanner.
- A4Tek Color Handscanner.
- This creates the audio devices used by the sound driver. These include mixer, sequencer, dsp, and audio.
- Generic SCSI devices. The devices created are sga through sgh and sg0 through sg7. These allow arbitary commands to be sent to any SCSI device. This allows for querying information about the device, or controlling SCSI devices that are not one of disk, tape or CDROM (e.g. scanner, CD-R, CD-RW).
- To allow an arbitary program to be fed input from file descriptor x, use /dev/fd/x as the file name. This also creates /dev/stdin, /dev/stdout, and /dev/stderr. (Note, these are just symlinks into /proc/self/fd).
- Devices (and symlinks) needed by the IBCS2 emulation.
- Devices for power management.
- Network Devices
- Linux used to have devices in /dev for controlling network devices, but that is no longer the case. To see what network devices are known by the kernel, look in /proc/net/dev.
- Other Devices
Note that the list of devices above is not exhaustive. MAKEDEV can create
more devices nodes. Its aim is to be able to create everything listed in the
devices.txt file distributed with Linux 2.4.
CONFIGURATIONMAKEDEV doesn't actually know anything about devices. It reads all of the information from files stored in /etc/makedev.d. MAKEDEV will read any and all files in the subdirectory, skipping over subdirectories, symbolic links, and device nodes, processing lines in the files like so:
mode owner group major minor inc count fmt [base]
count devices will be created, with permissions set to mode and owned by owner and group. The first device will be named fmt, and additional devices will be created if count is larger than 1. If fmt contains a C-style formatting string, it will be filled with the sum of base and zero. Subsequent devices will be filled with the sum of base and n * inc, where n is the order this device is being created in. If the format string did not already include a format specifier, a "%d" will automatically be appended to it to make this work.
- symbolic links
A symbolic link pointing to target named linkname will be created.
Any commands that create devices for alias will also include devices that would be crated for value.
Indicates a macro which can be referenced as $macro in subsequent configuration statements.
CONFIGURATION CONFLICTSIn the event that the set of configuration files contains multiple rules for a given device name, MAKEDEV will use all of them. The end result is typically that the last rule given (either by virtue of being listed below all other matching rules in the same file, or by being listed in a file which is read after all others which contain alternate rules) will apply. MAKEDEV reads the set of configuration files in sorted order, so this misfeature can be exploited dependably.
SEE ALSOLinux Allocated Devices, maintained by Torben Mathiasen <email@example.com>.
BUGSLet's hope not. If we're lucky, any problems we'll find will be confined to the configuration files, which were written by examining the devices.txt file. If your system uses udev, conflicts between devices.txt and the in-kernel data which udev uses for naming devices may crop up. If you find any bugs, please file them in the bug database at http://bugzilla.redhat.com/ against the "MAKEDEV" component.
AUTHORNalin Dahyabhai, based largely on work done by Nick Holloway and Michael K. Johnson.
- CONFIGURATION CONFLICTS
- SEE ALSO
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Time: 05:34:27 GMT, December 24, 2015