quartz/content/notes/05-filesystems.md

title	tags
05-filesystems	lecture cosc301

access control models

• DAC - subject centered
• MAC - object centered
• RBAC
• ACL
  • list of who can do what things to which files

backups

devices for file systems

• device naming conventions under /dev explanation
• full
  • easy, costly
• incremental
  • updates only files that have changed
  • level 0, 1, 2, 3, 4, 5 ... 9

UNIX file system

• tree
• descriptions
• implementation
  • inode ⇒ data structure documenting data about a file structure of directory
• current working DIR is always in memory

soft vs hard links

• hard link must always point to data - to delete a file with hard links you must also delete all the hard links
  • link to actual inode
• soft links can point to a non-existing file
  • link to file name
  • can link incompatible file systems e.g., windows, xerox. i.e. fs's that dont use inodes

advanced file attrs

special files

journaling

• logs changes to journal before writing
• impact on performance requires data be written twice
• question why not just write a description of the change
• all or nothing operations: ensure consistency

creating FS demo

• # dd if=/dev/zero of=loopbackfile.img bs=100M count=10
• # du -sh loopbackfile.img
• # losetup -fP loopbackfile.img
• # losetup –a
• # mkfs.ext4 /root/loopbackfile.img
• # mkdir /loopfs
• # df -hP /loopfs/
• # mount -o loop /dev/loop0 /loop
• # mount | grep loop