1 00:00:00,005 --> 00:00:02,007 - [Instructor] We're going to talk about the Linux kernel, 2 00:00:02,007 --> 00:00:04,009 a lot about the Linux kernel, 3 00:00:04,009 --> 00:00:08,006 and one of the important roles of the kernel is dealing 4 00:00:08,006 --> 00:00:12,004 with hardware, providing utilities, interfaces, 5 00:00:12,004 --> 00:00:14,009 protection for hardware. 6 00:00:14,009 --> 00:00:16,005 So let's just take a couple minutes 7 00:00:16,005 --> 00:00:20,004 and talk about some commands related to hardware, 8 00:00:20,004 --> 00:00:24,000 and these commands will often get information 9 00:00:24,000 --> 00:00:26,003 via the kernel. 10 00:00:26,003 --> 00:00:31,002 An application can call into the Linux kernel 11 00:00:31,002 --> 00:00:34,007 to give data or get data 12 00:00:34,007 --> 00:00:36,007 through functions like read and write, 13 00:00:36,007 --> 00:00:41,000 but those functions are implemented in a library 14 00:00:41,000 --> 00:00:43,001 for many binaries. 15 00:00:43,001 --> 00:00:46,000 They use the standard C library. 16 00:00:46,000 --> 00:00:51,002 And it's the library that knows how to invoke the kernel, 17 00:00:51,002 --> 00:00:56,003 and that involves typically architecture-dependent, 18 00:00:56,003 --> 00:00:58,002 similar language instruction approaches, 19 00:00:58,002 --> 00:01:01,002 doing a system call, a similar language instruction say 20 00:01:01,002 --> 00:01:04,003 to trap into the kernel. 21 00:01:04,003 --> 00:01:09,009 And the kernel is what controls devices typically. 22 00:01:09,009 --> 00:01:15,009 So the device drivers and Linux usually are in the kernel. 23 00:01:15,009 --> 00:01:18,006 So here's a few commands that might be handy 24 00:01:18,006 --> 00:01:20,009 to get information about hardware. 25 00:01:20,009 --> 00:01:24,003 So the commands would get information 26 00:01:24,003 --> 00:01:26,001 from the kernel somehow. 27 00:01:26,001 --> 00:01:31,000 List hardware, list PCI devices, list USB devices, 28 00:01:31,000 --> 00:01:34,007 list block devices, list CPU information, 29 00:01:34,007 --> 00:01:40,003 list other device informations like interrupt handler stuff. 30 00:01:40,003 --> 00:01:43,000 Now not all distros might have all these commands, 31 00:01:43,000 --> 00:01:46,004 but maybe yours does. 32 00:01:46,004 --> 00:01:50,003 You can also control hardware from the command line, 33 00:01:50,003 --> 00:01:52,009 asking the colonel to do things. 34 00:01:52,009 --> 00:01:58,005 The hdparm command is for getting information 35 00:01:58,005 --> 00:02:05,000 and setting tunables, controlling, discs. 36 00:02:05,000 --> 00:02:10,002 There's also lots of files underneath proc, dev, 37 00:02:10,002 --> 00:02:15,003 and the assist file system that the kernel provides. 38 00:02:15,003 --> 00:02:18,004 These are all pseudo file systems. 39 00:02:18,004 --> 00:02:23,004 The kernel provides information there about devices 40 00:02:23,004 --> 00:02:25,009 and many files there are writeable 41 00:02:25,009 --> 00:02:30,000 so that you can change configurations 42 00:02:30,000 --> 00:02:33,003 or tuneable values in the kernel. 43 00:02:33,003 --> 00:02:35,001 And there's also kind 44 00:02:35,001 --> 00:02:38,000 of classic lower level functionality like inb 45 00:02:38,000 --> 00:02:40,006 and outb for talking to special kind 46 00:02:40,006 --> 00:02:43,008 of input devices like keyboards. 47 00:02:43,008 --> 00:02:46,009 And there's even utilities to deal more directly 48 00:02:46,009 --> 00:02:50,002 with PCI devices, set PCI for example. 49 00:02:50,002 --> 00:02:54,007 So you can do much of what a PCI device driver would do, 50 00:02:54,007 --> 00:02:58,000 you know, from the command line in a shell script. 51 00:02:58,000 --> 00:03:00,006 Let's look at the commands little bit. 52 00:03:00,006 --> 00:03:04,001 All right, so some of these you want to do as root. 53 00:03:04,001 --> 00:03:08,000 So we'll do a sudo, list hardware. 54 00:03:08,000 --> 00:03:12,000 This got an idea of how many lines will come out. 55 00:03:12,000 --> 00:03:14,006 282 lines. So there's quite a bit of stuff there. 56 00:03:14,006 --> 00:03:19,009 We'll just look at this a bit. 57 00:03:19,009 --> 00:03:24,002 All right, so at the top there's the name of this VM. 58 00:03:24,002 --> 00:03:26,005 Thinks it's a desktop computer. 59 00:03:26,005 --> 00:03:29,002 We're looking at motherboard and firmware 60 00:03:29,002 --> 00:03:33,004 and CPU information and lots more. 61 00:03:33,004 --> 00:03:37,006 For PCI devices, I often do the minus V 62 00:03:37,006 --> 00:03:40,004 for verbose, get a little more information. 63 00:03:40,004 --> 00:03:43,009 And on this VM, it thinks there's only one PCI device, 64 00:03:43,009 --> 00:03:50,007 ethernet device and block devices. 65 00:03:50,007 --> 00:03:53,007 We got the loop devices, which are not really devices, 66 00:03:53,007 --> 00:04:00,009 and then we got discs, SDA, SDB, SDC, SDD. 67 00:04:00,009 --> 00:04:07,008 So this VM has a bunch of discs. 68 00:04:07,008 --> 00:04:12,004 Let's do LSCPU, find out about our CPUs. 69 00:04:12,004 --> 00:04:14,006 And you know, lots of information there. 70 00:04:14,006 --> 00:04:15,009 There's even some information 71 00:04:15,009 --> 00:04:22,008 about CPU vulnerabilities reported, LS dev. 72 00:04:22,008 --> 00:04:24,004 So this is device information. 73 00:04:24,004 --> 00:04:28,009 You can see 'em listed and IO ports. 74 00:04:28,009 --> 00:04:33,004 Let's see the difference when we use sudo. 75 00:04:33,004 --> 00:04:37,005 Then we get real addresses, IO ports, so forth. 76 00:04:37,005 --> 00:04:41,000 IO ports is what you could manipulate with the NB 77 00:04:41,000 --> 00:04:43,008 and LB stuff, but that's pretty ancient sort 78 00:04:43,008 --> 00:04:44,009 of things to do. 79 00:04:44,009 --> 00:04:50,004 But we got timers, we've got a real time clock and so forth. 80 00:04:50,004 --> 00:04:54,008 Let's find out information about a disc with hdparm, 81 00:04:54,008 --> 00:05:00,001 so the capital I option. 82 00:05:00,001 --> 00:05:02,006 And we see some information about there. 83 00:05:02,006 --> 00:05:04,004 Not a whole lot. 84 00:05:04,004 --> 00:05:09,003 This is a VM, but hdparm has lots of options, 85 00:05:09,003 --> 00:05:12,000 so you could do quite a lot there. 86 00:05:12,000 --> 00:05:17,000 And then as an example of a tuneable down 87 00:05:17,000 --> 00:05:23,002 in the sys file system, we can try one. 88 00:05:23,002 --> 00:05:27,005 So way underneath, sys devices, yada, yada, yada, 89 00:05:27,005 --> 00:05:32,004 there is a file called max retries 90 00:05:32,004 --> 00:05:36,000 that has to do with how many times a file system 91 00:05:36,000 --> 00:05:38,009 or a driver will retry an operation 92 00:05:38,009 --> 00:05:40,007 on that disc if it fails. 93 00:05:40,007 --> 00:05:45,000 And we can see here it's currently set to try five times. 94 00:05:45,000 --> 00:05:45,008 There you go. 95 00:05:45,008 --> 00:05:47,000 That was a quick look 96 00:05:47,000 --> 00:05:51,009 at a few hardware related utilities, sort of things 97 00:05:51,009 --> 00:05:55,000 that ask the colonel for help.