This is the unformatted notes....
Finishing off last week
A little exercise with initrd cd /var/tmp mkdir initrd cd initrd gunzip < /boot/initrd.img-3.13.0-100-generic | cpio -id du -s * Take a look at bin directory what is busybox? init shellscript it will call /bin/run-init to run /sbin/init It is process #1 https://en.wikipedia.org/wiki/Init https://en.wikipedia.org/wiki/Systemd https://www.digitalocean.com/community/tutorials/understanding-systemd-units-and-unit-files systemd is the future — (it spite of the screaming) Fedora (2011), Red Hat (2014), Debian/Ubuntu/Raspbian (2015) Still many System V compatiability modes Connect to eastatoe.cs.unca.edu and look at /lib/systemd/services
Devices – Chapter 3
mknod /proc/devices https://github.com/torvalds/linux/tree/master/drivers https://github.com/torvalds/linux/blob/master/drivers/char/mem.c Look for read_null and write_null and null_lseek and null_fops similarly for zero_fops and full_fops and memdev structure (l 806) https://github.com/torvalds/linux/blob/master/drivers/char/random.c cat /dev/zero echo foo > /dev/zero echo foo > /dev/null cat /dev/null dd if=/dev/zero of=zero.chars bs=1000 count=1 ls -l /dev | grep " 1," /proc/filesystems https://github.com/torvalds/linux/tree/master/fs/sysfs /sys — sysfs /proc — procfs debugfs — /sys/kernel/debug devpts — /dev/pts Take a look at /sys — the sys filesystem In /sys/bus WHAT ARE THEY.... acpi i2c What is /sys/fs cgroup, ecryptfs, ext4, fuse, pstore What is /sys/module What is a block vs character device? block devices may "cache" blocks in RAM take a look at the "top" command What is a bus? What are all the buses (in /sys/bus) Look at Section 3.4 What are the disks on your system Try lsscsi https://en.wikipedia.org/wiki/SCSI_command http://www.seagate.com/staticfiles/support/disc/manuals/Interface%20manuals/100293068c.pdf SCSI addresses by LBA not CHS https://en.wikipedia.org/wiki/Cylinder-head-sector What does this mean? /sys/devices/pci0000:00/0000:00:1d.7/usb2/2-2/2-2:1.0/host12/target12:0:0/12:0:0:0/block/sdc What is the northbridge and southbridge Intel 4 Series Chipset http://www.intel.com/content/www/us/en/processors/xeon/4-chipset-family-datasheet.html Intel Z270 chipset http://ark.intel.com/products/98089/ http://www.intel.com/content/www/us/en/chipsets/200-series-chipset-pch-datasheet-vol-1.html Back to USB — what does the name mean? http://www.makelinux.net/ldd3/chp-13-sect-2 mknod create devices What can't ordinary users create devices? Why aren't devices allowed on USB drives? Section 3.5 — by the book In the old days, you didn't add devices to running systems lsusb What is that device? (vendor + class) https://usb-ids.gowdy.us udev — dynamic device management man udev /etc/udev/rules.d/ udevadm — may need a USB device udevadm info —query=all —name=/dev/sda udevadm monitor Look at udev-out.txt Look at Figure 3-2
Disks, partitions, and file systems — Chapter 4
Why partitions? http://www.digitalcitizen.life/4-reasons-why-you-should-use-more-one-partition-your-pc The MBR (Master Book Record) world Primary partitions — up to 4 Extended partition — 1 special primary partition Logical partitions — a division of an extended partition The GPT (Globally unique identifier Partition Table) Other stuff —- lvm — logical volume manager (look at the lab computer) https://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux) hardware RAID — on the server computers software RAID ZFS and AdvFS (defunct) https://en.wikipedia.org/wiki/ZFS https://en.wikipedia.org/wiki/AdvFS Try out the Raspberry Pi sudo /sbin/fdisk /dev/mmcblk0 Do not WRITE! A partition exercise — Two year’s ago DANGER. DANGER. YOU MUST WATCH ME...