1 00:00:00,002 --> 00:00:05,005 (bouncy upbeat music) 2 00:00:05,005 --> 00:00:09,001 - [Instructor] Let's look at solutions for those challenges. 3 00:00:09,001 --> 00:00:15,004 So we want to know what files LSPCI opens 4 00:00:15,004 --> 00:00:17,001 and we're maybe particularly interested 5 00:00:17,001 --> 00:00:19,004 in files underneath /sys. 6 00:00:19,004 --> 00:00:23,006 But let's see. What's strace. 7 00:00:23,006 --> 00:00:28,009 We're going to do all the openat lspci. 8 00:00:28,009 --> 00:00:31,006 Not a whole lot of them, some library stuff, 9 00:00:31,006 --> 00:00:36,006 but we see several SIS bus PCI devices 10 00:00:36,006 --> 00:00:38,007 sort of things opened. 11 00:00:38,007 --> 00:00:43,005 So it's looking for PCI devices using the SIS file system. 12 00:00:43,005 --> 00:00:49,005 Also, by the way, it opens users share miscellaneous pci.ids 13 00:00:49,005 --> 00:00:54,006 to get the names that correspond to the code 14 00:00:54,006 --> 00:00:59,003 for things like the vendor name for PCI devices. 15 00:00:59,003 --> 00:01:03,003 Now we want to look at sysblock. 16 00:01:03,003 --> 00:01:05,001 We do a list there. 17 00:01:05,001 --> 00:01:08,007 We see our block devices and we see an sda, right? 18 00:01:08,007 --> 00:01:11,001 That's a soft link but yeah, 19 00:01:11,001 --> 00:01:16,008 we have a sda disc block device on this system. 20 00:01:16,008 --> 00:01:22,004 Let's go in there and we see sub directories, 21 00:01:22,004 --> 00:01:27,005 for its partitions, sda1, sda2, sda3. 22 00:01:27,005 --> 00:01:31,004 Great, got three partitions. 23 00:01:31,004 --> 00:01:37,000 Let's look at what fdisk -l opens. 24 00:01:37,000 --> 00:01:42,003 strace - e openat output, 25 00:01:42,003 --> 00:01:44,008 what to put it in temp. 26 00:01:44,008 --> 00:01:47,001 We can't write into the directory we're in right now, 27 00:01:47,001 --> 00:01:52,000 sys block sda, can't create a file there 28 00:01:52,000 --> 00:01:57,009 and we want to run fdisk -l. 29 00:01:57,009 --> 00:02:01,002 Alright, now we want to see if that fdisk -l 30 00:02:01,002 --> 00:02:04,007 opened anything underneath sys block. 31 00:02:04,007 --> 00:02:12,005 So let's grab sys/block in that strace file. 32 00:02:12,005 --> 00:02:14,002 It opened a lot. 33 00:02:14,002 --> 00:02:15,006 It also failed to open a lot. 34 00:02:15,006 --> 00:02:17,003 Look, for example, it tried to open 35 00:02:17,003 --> 00:02:23,004 sysblock sda3 device dev sysblock, sda, 36 00:02:23,004 --> 00:02:24,005 those are all failing. 37 00:02:24,005 --> 00:02:27,006 No such file directory. What's up with that? 38 00:02:27,006 --> 00:02:30,004 All right, so sysblock sda3. 39 00:02:30,004 --> 00:02:34,003 If we go back, there's no entries here 40 00:02:34,003 --> 00:02:38,006 for the partitions, so there's no sysblock sda3. 41 00:02:38,006 --> 00:02:42,001 sda3 is underneath sda. 42 00:02:42,001 --> 00:02:46,006 So if fdisk were looking for information about sda1, 43 00:02:46,006 --> 00:02:51,003 it should be trying to open sysblock sda sda1. 44 00:02:51,003 --> 00:02:52,005 That looks like a little problem 45 00:02:52,005 --> 00:02:56,002 with the fdisk utility to me. 46 00:02:56,002 --> 00:02:59,008 And if we look in sda1, 47 00:02:59,008 --> 00:03:02,004 sure enough, there is a dev file there. 48 00:03:02,004 --> 00:03:05,007 So it could have been looking there. 49 00:03:05,007 --> 00:03:09,006 The other question was does fdisk -l 50 00:03:09,006 --> 00:03:12,004 open anything in cis dev block? 51 00:03:12,004 --> 00:03:17,001 So let's grip sys dev block 52 00:03:17,001 --> 00:03:19,005 in the strace output. 53 00:03:19,005 --> 00:03:22,004 Yep, it opens a bunch of things there. 54 00:03:22,004 --> 00:03:26,006 All these names that are number:number, 55 00:03:26,006 --> 00:03:27,005 we'll talk about that. 56 00:03:27,005 --> 00:03:29,007 That's major and minor number. 57 00:03:29,007 --> 00:03:33,003 That's device file sort of information. 58 00:03:33,003 --> 00:03:37,000 But yeah, fdisk tries to open lots of files. 59 00:03:37,000 --> 00:03:38,000 There you go.