Thank you for your interest in DragonFly! The following chapter covers various aspects of the DragonFly Project, such as its history, goals, development model, and so on. DragonFly is a 4. One of the variants that became quite popular became known later as FreeBSD.
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Updated and restructured by Jim Mock. Originally contributed by Jake Hamby. The kernel is the core of the DragonFly operating system. It is responsible for managing memory, enforcing security controls, networking, disk access, and much more. While more and more of DragonFly becomes dynamically configurable it is still occasionally necessary to reconfigure and recompile your kernel. Traditionally, DragonFly has had what is called a monolithic kernel.
This means that the kernel was one large program, supported a fixed list of devices, and if you wanted to change the kernel's behavior then you had to compile a new kernel, and then reboot your computer with the new kernel.
Today, DragonFly is rapidly moving to a model where much of the kernel's functionality is contained in modules which can be dynamically loaded and unloaded from the kernel as necessary. This allows the kernel to adapt to new hardware suddenly becoming available such as PCMCIA cards in a laptop , or for new functionality to be brought into the kernel that was not necessary when the kernel was originally compiled.
This is known as a modular kernel. Colloquially these are called KLDs. Despite this, it is still necessary to carry out some static kernel configuration. In some cases this is because the functionality is so tied to the kernel that it can not be made dynamically loadable. In others it may simply be because no one has yet taken the time to write a dynamic loadable kernel module for that functionality yet.
This process, while time consuming, will provide many benefits to your DragonFly system. Unlike the generic kernel, which must support a wide range of hardware, a custom kernel only contains support for your PC's hardware. This has a number of benefits, such as:. First, let us take a quick tour of the kernel build directory. There are a number of subdirectories here representing different parts of the kernel, but the most important, for our purposes, is config , where you will edit your custom kernel configuration, and compile , which is the staging area where your kernel will be built.
Notice the logical organization of the directory structure, with each supported device, file system, and option in its own subdirectory. One method to do this is via git. An alternative is to install the kernel source tree from the archive distributed on the DragonFly CD named src-sys.
This is especially useful when you do not have ready access to the internet. When installing kernel source only, use the alternate build procedure below. This method also allows for easy updating of the source tree by using:. For example:. Traditionally, this name is in all capital letters and, if you are maintaining multiple DragonFly machines with different hardware, it is a good idea to name it after your machine's hostname.
Five seconds after you do that you realize that you have deleted your custom kernel config file. You might want to keep your kernel config file elsewhere, and then create a symbolic link to the file in the config directory. Note: You must execute these and all of the following commands under the root account or you will get permission denied errors. If you are just starting out and are not familiar with vi , you can use an easier editor called ee , which is also part of the base system.
In this file all important issues with updating DragonFly are typed out. Note: Use -j N to parallelize the build targets. We don't recommend -j N and there is no need for it either for the install targets.
If you have not upgraded your source tree in any way since the last time you successfully completed a buildworld - installworld cycle you have not run git pull , then it is safe to use the quickworld and quickkernel , buildworld , buildkernel sequence.
Now, shutdown the system and reboot to use your new kernel. In case something goes wrong, there are some troubleshooting instructions at the end of this chapter. Be sure to read the section which explains how to recover in case your new kernel does not boot. For more information, take a look at device nodes section later on in this chapter. The general format of a configuration file is quite simple. Each line contains a keyword and one or more arguments.
For simplicity, most lines only contain one argument. Anything following a is considered a comment and ignored. If you are in doubt as to the purpose or necessity of a line, check first in LINT This is the identification of the kernel. You should change this to whatever you named your kernel, i.
The value you put in the ident string will print when you boot up the kernel, so it is useful to give the new kernel a different name if you want to keep it separate from your usual kernel i. The maxusers option sets the size of a number of important system tables.
This number is supposed to be roughly equal to the number of simultaneous users you expect to have on your machine. The system will auto-tune this setting for you if you leave it to 0 , which is recommended the auto-tuning algorithm sets maxuser equal to the amount of memory in the system, with a minimum of 32, and a maximum of If you want to manage it yourself you will want to set maxusers to at least 4, especially if you are using the X Window System or compiling software.
Even a simple task like reading a manual page will start up nine processes to filter, decompress, and view it. Setting maxusers to 64 will allow you to have up to simultaneous processes, which should be enough for nearly all uses.
If, however, you see the dreaded proc table full error when trying to start another program, or are running a server with a large number of simultaneous users, you can always increase the number and rebuild. Note: maxusers does not limit the number of users which can log into your machine. It simply sets various table sizes to reasonable values considering the maximum number of users you will likely have on your system and how many processes each of them will be running.
One keyword which does limit the number of simultaneous remote logins and X terminal windows is pseudo-device pty 16 see below. If you telnet or FTP to localhost a. This is mandatory. Everything that follows is more or less optional.
See the notes underneath or next to each option for more information. The normal build process of the DragonFly does not include debugging information when building the kernel and strips most symbols after the resulting kernel is linked, to save some space at the install location. Networking support.
Leave this in, even if you do not plan to be connected to a network. Most programs require at least loopback networking i. This option includes functionality to speed up disk operations on large directories, at the expense of using additional memory.
You would normally keep this for a large server, or interactive workstation, and remove it if you are using DragonFly on a smaller system where memory is at a premium and disk access speed is less important, such as a firewall.
This option enables Soft Updates in the kernel, this will help speed up write access on UFS file systems. Even when this functionality is provided by the kernel, it must be turned on for specific disks. Review the output from mount 8 to see if Soft Updates is enabled for your system disks.
If you do not see the soft-updates option then you will need to activate it using the tunefs 8 for existing filesystems or newfs 8 for new filesystems commands. This is the memory-mapped filesystem. This is basically a RAM disk for fast storage of temporary files, useful if you have a lot of swap space that you want to take advantage of.
The network Filesystem. Unless you plan to mount a DOS-formatted hard drive partition at boot time, you can safely comment this out. It will be automatically loaded the first time you mount a DOS partition, as described above. Audio CDs do not need this Filesystem.
The process filesystem. Compatibility with 4. This should not be needed nowadays, but might be required for some old programs. This causes the kernel to pause for 5 seconds before probing each SCSI device in your system. You may try to lower this number to speed up booting; of course, if you do this and DragonFly has trouble recognizing your SCSI devices, you will have to raise it back up. This is useful for X users. For example, you can create a console xterm by typing xterm -C , which will display any write 1 , talk 1 , and any other messages you receive, as well as any console messages sent by the kernel.
This option provides for System V shared memory. The most common use of this is the XSHM extension in X, which many graphics-intensive programs will automatically take advantage of for extra speed. If you use X, you will definitely want to include this. Support for System V semaphores. Less commonly used but only adds a few hundred bytes to the kernel. Note: The ipcs 1 command will list any processes using each of these System V facilities. This option enables ICMP error response bandwidth limiting.
You typically want this option as it will help protect the machine from denial of service packet attacks. All PCs supported by DragonFly have one of these. Do not remove, even if you have no ISA slots. Include this if you have a PCI motherboard. Include this if you have an AGP card in the system. This makes the controller number static like the old driver or else the device numbers are dynamically allocated. SCSI controllers. Comment out any you do not have in your system.
Updated and restructured by Jim Mock. Originally contributed by Jake Hamby. The kernel is the core of the DragonFly operating system. It is responsible for managing memory, enforcing security controls, networking, disk access, and much more.