1 00:00:00,005 --> 00:00:04,006 - [Instructor] Let's look at configuring your Linux kernel. 2 00:00:04,006 --> 00:00:07,004 So there's a variety of tools for that. 3 00:00:07,004 --> 00:00:12,001 My favorite one is the old school make menuconfig. 4 00:00:12,001 --> 00:00:14,005 So notice we're using the make command. 5 00:00:14,005 --> 00:00:18,001 When you say make menuconfig the first time, 6 00:00:18,001 --> 00:00:22,007 then it will get compiled and built as an executable. 7 00:00:22,007 --> 00:00:26,000 So you might have to have some extra stuff installed 8 00:00:26,000 --> 00:00:28,009 for that to happen. 9 00:00:28,009 --> 00:00:30,000 And then when it runs, 10 00:00:30,000 --> 00:00:33,002 you're going to get this sort of interface, 11 00:00:33,002 --> 00:00:35,008 and you can move around with your arrow keys 12 00:00:35,008 --> 00:00:38,000 and so forth, right? 13 00:00:38,000 --> 00:00:40,001 So it's not mouse-oriented. 14 00:00:40,001 --> 00:00:42,007 It's ncurses-oriented. 15 00:00:42,007 --> 00:00:44,000 That's a package you install 16 00:00:44,000 --> 00:00:47,002 so you can use your arrow keys. 17 00:00:47,002 --> 00:00:50,002 And there's a whole tree of choices, 18 00:00:50,002 --> 00:00:51,007 so you can hit Enter 19 00:00:51,007 --> 00:00:54,008 to go down through the trees and so forth 20 00:00:54,008 --> 00:00:57,004 and Escape to go back up. 21 00:00:57,004 --> 00:01:01,009 I'll demo this all for you a little bit later. 22 00:01:01,009 --> 00:01:05,002 If you look at the interface, you will see for choices, 23 00:01:05,002 --> 00:01:09,009 there's sometimes less than greater than or angle brackets, 24 00:01:09,009 --> 00:01:13,007 and sometimes there's square brackets. 25 00:01:13,007 --> 00:01:15,001 When there's angle brackets, 26 00:01:15,001 --> 00:01:17,002 that means there's three choices. 27 00:01:17,002 --> 00:01:22,005 You can have an asterisk, an M, or blank. 28 00:01:22,005 --> 00:01:28,005 Blank means that configuration option is not turned on. 29 00:01:28,005 --> 00:01:32,000 M means you've chosen it to be compiled 30 00:01:32,000 --> 00:01:34,006 as a loadable kernel module. 31 00:01:34,006 --> 00:01:37,003 And asterisk means you've chosen it 32 00:01:37,003 --> 00:01:41,007 to be built into the kernel image itself. 33 00:01:41,007 --> 00:01:43,006 When it's square brackets, 34 00:01:43,006 --> 00:01:45,006 all right, it's an asterisk or blank. 35 00:01:45,006 --> 00:01:47,002 Either you have it or you don't. 36 00:01:47,002 --> 00:01:49,008 That's just a Boolean. 37 00:01:49,008 --> 00:01:52,002 Sometimes you'll see options grayed out 38 00:01:52,002 --> 00:01:55,002 or maybe not even showing up that you know that are there. 39 00:01:55,002 --> 00:01:58,001 That's a little bit confusing. 40 00:01:58,001 --> 00:02:00,001 It turns out there's dependencies 41 00:02:00,001 --> 00:02:02,002 between configuration options. 42 00:02:02,002 --> 00:02:04,005 You might have to enable one thing 43 00:02:04,005 --> 00:02:08,004 for something else to even be possible. 44 00:02:08,004 --> 00:02:13,000 So although your choices are all saved in .config, 45 00:02:13,000 --> 00:02:15,008 you typically don't want to edit .config by hand 46 00:02:15,008 --> 00:02:20,007 because, for one thing, you might mess up the dependencies. 47 00:02:20,007 --> 00:02:24,002 So generally, use one of the config tools 48 00:02:24,002 --> 00:02:27,008 or a command line way to edit stuff, 49 00:02:27,008 --> 00:02:31,006 but mostly I use make menuconfig. 50 00:02:31,006 --> 00:02:33,007 The kind of primitive interface 51 00:02:33,007 --> 00:02:35,008 in make menuconfig does have a search. 52 00:02:35,008 --> 00:02:39,000 You can say / and then give a string, 53 00:02:39,000 --> 00:02:41,005 and it will find you the configuration options 54 00:02:41,005 --> 00:02:43,002 with that string. 55 00:02:43,002 --> 00:02:45,006 And it gives you a little bit of documentation, 56 00:02:45,006 --> 00:02:46,009 like where they are, 57 00:02:46,009 --> 00:02:49,009 underneath what part of the configuration tree 58 00:02:49,009 --> 00:02:51,009 and it's type. 59 00:02:51,009 --> 00:02:53,005 A Boolean means it's going to be 60 00:02:53,005 --> 00:02:56,001 in square brackets, for example. 61 00:02:56,001 --> 00:02:57,008 And all this information 62 00:02:57,008 --> 00:03:02,009 that make menuconfig uses comes from Kconfig files 63 00:03:02,009 --> 00:03:05,000 spread out all through the file system. 64 00:03:05,000 --> 00:03:07,002 So when you look at Kconfig files in a directory, 65 00:03:07,002 --> 00:03:10,004 you can see what in that directory 66 00:03:10,004 --> 00:03:13,004 can be configured and how. 67 00:03:13,004 --> 00:03:17,007 The developers have often kindly added some advice 68 00:03:17,007 --> 00:03:21,009 about choices for configuration, some help information. 69 00:03:21,009 --> 00:03:25,001 Sometimes there isn't any, but oftentimes there is, 70 00:03:25,001 --> 00:03:26,003 and it gives you some information 71 00:03:26,003 --> 00:03:28,005 about what that option does 72 00:03:28,005 --> 00:03:30,005 and some advice as to whether, 73 00:03:30,005 --> 00:03:31,004 if you don't know what it is, 74 00:03:31,004 --> 00:03:32,008 whether you should do it or not. 75 00:03:32,008 --> 00:03:34,007 Sometimes it says, "If you don't know what this is, 76 00:03:34,007 --> 00:03:36,008 don't do it." 77 00:03:36,008 --> 00:03:39,008 With make menuconfig, 78 00:03:39,008 --> 00:03:44,000 you exit out with escaping 79 00:03:44,000 --> 00:03:46,002 and hitting the exit on the bottom. 80 00:03:46,002 --> 00:03:50,001 And at the very end, the top level, 81 00:03:50,001 --> 00:03:51,006 it will ask you if you want to save, 82 00:03:51,006 --> 00:03:53,004 and it'll save to the .config. 83 00:03:53,004 --> 00:03:54,003 That's the default. 84 00:03:54,003 --> 00:03:55,003 That's the usual thing you do. 85 00:03:55,003 --> 00:03:57,003 You just exit out. 86 00:03:57,003 --> 00:04:00,001 You can save to an alternate config file 87 00:04:00,001 --> 00:04:02,007 if you want to make a copy of it. 88 00:04:02,007 --> 00:04:08,000 And it's also possible to load an alternate config file, 89 00:04:08,000 --> 00:04:10,008 but typically, I just exit out 90 00:04:10,008 --> 00:04:14,000 and accept saving to .config.