1. A Primer for Beginners Paul W. Frields Presented by Red Hat,
Inc. Licensed under a Creative Commons Attribution-ShareAlike
(BY-SA) 3.0 license. http://creativecommons.org/by-sa/3.0/ Linux
File Systems
2. Today's Topics Disks and partitions Logical Volume
Management (LVM) File system formats Concentration is on practical
use by home/desktop users
3. Disks and Partitions
4. What kind of disks? SATA most laptops and home desktops)
IDE, SCSI mainly outdated Fibre Channel, Infiniband, and others
high end In most cases, your hard disk is probably the device node
/dev/sda
5. RAID Redundant Array of Inexpensive Disks Combine two or
more disks into a group that is managed together Sacrifices storage
capacity for fault tolerance Avoid for today this is an hour on its
own!
6. What are partitions? Divide your disk into usable areas A
map/table at the top describes the layout In complex setups (>4
partitions), it becomes a linked list Most dual-boot systems fall
into this category Each successive table points to another table
further down the disk, and so on...
7. You need three /boot used to bootstrap the GRUB loader and
kernel swap used by the kernel to shift older data out of RAM when
memory gets tight / (also called root) everything else can be
stored here
8. Everything in root? Linux does not have a C: drive, D:
drive... Everything is unified under top level / folder Under this,
/bin, /etc, /var, etc. How you break up file systems under this is
up to you lets look at reasons for and against...
9. Why break things up? Guard against out of space problems
that might affect the running system Lets you re-install OS without
touching data (try that on Windows with just a C: drive!)
10. Why not? Complexity of understanding partitions Complexity
of management Figuring out where you ran out of space Figuring out
where you need more space But, I have a 640 GB drive, it cant be
full!
11. Whats on your disk? (df)
12. Installer defaults Depends on the Linux distro Most
installers pick a good default DONT worry about it if you dont have
to DO note the layout so you can understand implications
13. Disks tool
14. LVM Logical Volume Management Turns storage into areas that
can be flexibly adjusted after the fact Dont use this for /boot or
swap Some installers use by default Generally a good idea since you
may want to reallocate space later Adds a level of abstraction
(complexity)
15. LVM concepts PV (physical volume) a partition or disk thats
been added to the LVM pool VG (volume group) one or more PVs
connected under a single name and managed together LV (logical
volume) a portion of a VG which is formatted with a file system
(like a partition would be)
18. LVM system files Boot time use of LVM defined in /etc/lvm
directory /etc/lvm/lvm.conf general configuration
/etc/lvm/backup/vg_name backup of VG definition (sizes, locations)
CAREFUL! /etc/lvm/archive stores previous definitions of VGs
19. Whats on your disk? (LVM)
20. Formatted file systems Live on a partition or LVM logical
volume (LV) Provide orderly arrangement of files Usually
hierarchical (folders, subfolders) Store file data and metadata
(timestamps, security details, size, etc.) Examples are ext3fs,
ext4fs, btrfs, NTFS, FAT varieties
21. Linux and other OSs Linux reads and writes most other OS
file systems out of the box The opposite is not necessarily true!
You can get drivers for Linux file systems for Windows, MacOS
22. FAT and NTFS Used primarily by Windows Also removable media
where manufacturer cant guess your OS (85-90% case) NTFS is needed
for larger storage (>4 GB)
23. HFS+ and beyond Apple MacOS Older HFS is quite rare
nowadays but still supported in Linux (moving to reaonly)
24. ext3 and ext4 Standard Linux file systems Older ext2 not
used as much anymore although its basically compatible with ext3
ext3 added journaling capability ext4 supports much larger file
systems
25. What is btrfs? Pronounced better or butter eff ess Uses
more modern file system design similar to e.g. XFS to achieve
higher levels of scalability and performance for modern workloads
Still adding features and stability Chances are you wont need to
decide to use; your distro will pick if/when necessary
26. File system utilities Show disk free space (df) Show disk
usage by files (du) Make a file system (mkfs) File system
check/repair (fsck) Mount/unmount file system (mount/umount) The
mount utility also shows curent mounts
27. Mounts All separate formatted file systems, when mounted,
are part of the single hierarchy A file system can be mounted on
any directory as a mount point System defined mounts (used at boot)
in the /etc/fstab file
28. Whats on your disk? (mounts)
29. Summary Disks can be divided up into partitions Partitions
can be combined and split into LVM storage Partitions or LVM
logical volumes are mounted on the system to store files