Unadorned links for February 28, 2017

Homework

Grading homeworks 2, 3 and 4 continued

Pi for all

Find your own Pi! If you are in a group, help everyone to split the Pi.

There are 23 students in the class. There used to be 15 Pi’s; now there are 27. Also, Raspberry Pi systems can be replaced with Raspberry Pi3 systems!

1. uncacsci-pi-a
2. uncacsci-pi-b — 1 account
3. uncacsci-pi-c
4. uncacsci-pi-e — 2 accounts
5. uncacsci-pi-g — 3 accounts
6. uncacsci-pi-h — 3 accounts
7. uncacsci-pi-k
8. uncacsci-pi-o — 2 accounts
9. uncacsci-pi-p — 2 accounts
10. uncacsci-pi-q
11. uncacsci-pi-r — 1 account
12. uncacsci-pi-u — 1 account
13. uncacsci-pi-v — 2 accounts
14. uncacsci-pi-w
15. uncacsci-pi-y — 1 account
16. uncacsci-pi2-a
17. uncacsci-pi2-b
18. uncacsci-pi2-c
19. uncacsci-pi2-d
20. uncacsci-pi2-e
21. uncacsci-pi2-f
22. uncacsci-pi2-g
23. uncacsci-pi2-h
24. uncacsci-pi3-a
25. uncacsci-pi3-b
26. uncacsci-pi3-c

File systems

• Comparison of file systems
• Design of File Allocation Table (FAT) file system
• Microsoft EFI FAT32 File System Specification
• ext4 disk layout
• extents, sequential lists, trees, extants
• Directory search — sequential list, b-trees, Htrees
• Journaling

What is the OS (Linux) view of a file (again)

Not so quick answers

• Call Python’s os.stat() and use the stat module to pull out useful information
• Run the stat program

Links — pointers for files

• device id and inode numbe — “address” of a file
• reference counts — number of hard links
• symbolic links — soft links
• Using the ln command
• Making links with Python with the os module — os.link

Access Control Lists

• Required for SELinux
• getfacl and setfacl
• You better just find some examples to ponder
• task — make a file than can only be read by you and two others

just checking

Have you written Python programs to read and write files?

• io tutorial
• io module

A lab part

Disecting a file system

Try to work to the root directory part of the finding a file exercise.

Getting an account

Find your own Pi. Create your own personal account on your own computer.

A file exercise — Homework 7

Make sure your Pi doesn’t have any logical volumes. Run pvscan, vgscan and lvscan to find logical volume structures. Use lvremove, vgremove and pvremove to delete them.

Keep the partitions for / (/dev/mmcblk0p2) and /boot (/dev/mmcblk0p1); but delete all others.

Partition your Pi to match the following and then reboot.

Device         Boot    Start      End  Sectors  Size Id Type
/dev/mmcblk0p1          8192   131071   122880   60M  c W95 FAT32 (LBA)
/dev/mmcblk0p2        131072 16908287 16777216    8G 83 Linux
/dev/mmcblk0p3      16908288 27394047 10485760    5G 83 Linux
/dev/mmcblk0p4      27394048 31422463  4028416  1.9G 83 Linux

Now format /dev/mmcblk0p4 to be an ext4 file system.

Within the /dev/mmcblk0p3 partition create a volume group csci373VG with three logical volumes: msdos373LV with 32 MB, ext373LV with 2 MB, and xfs373LV with 2 MB.