From the course: Advanced Linux: The Linux Kernel

Solution: sysfs - Linux Tutorial

From the course: Advanced Linux: The Linux Kernel

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Solution: sysfs

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(bouncy upbeat music) - [Instructor] Let's look at solutions for those challenges. So we want to know what files LSPCI opens and we're maybe particularly interested in files underneath /sys. But let's see. What's strace. We're going to do all the openat lspci. Not a whole lot of them, some library stuff, but we see several SIS bus PCI devices sort of things opened. So it's looking for PCI devices using the SIS file system. Also, by the way, it opens users share miscellaneous pci.ids to get the names that correspond to the code for things like the vendor name for PCI devices. Now we want to look at sysblock. We do a list there. We see our block devices and we see an sda, right? That's a soft link but yeah, we have a sda disc block device on this system. Let's go in there and we see sub directories, for its partitions, sda1, sda2, sda3. Great, got three partitions. Let's look at what fdisk -l opens. strace - e openat output, what to put it in temp. We can't write into the directory we're in right now, sys block sda, can't create a file there and we want to run fdisk -l. Alright, now we want to see if that fdisk -l opened anything underneath sys block. So let's grab sys/block in that strace file. It opened a lot. It also failed to open a lot. Look, for example, it tried to open sysblock sda3 device dev sysblock, sda, those are all failing. No such file directory. What's up with that? All right, so sysblock sda3. If we go back, there's no entries here for the partitions, so there's no sysblock sda3. sda3 is underneath sda. So if fdisk were looking for information about sda1, it should be trying to open sysblock sda sda1. That looks like a little problem with the fdisk utility to me. And if we look in sda1, sure enough, there is a dev file there. So it could have been looking there. The other question was does fdisk -l open anything in cis dev block? So let's grip sys dev block in the strace output. Yep, it opens a bunch of things there. All these names that are number:number, we'll talk about that. That's major and minor number. That's device file sort of information. But yeah, fdisk tries to open lots of files. There you go.

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