Curriculum

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====== Disk, Partition, File System ======

===== Disk =====

A disk is a block device.

== fdisk ==

Used to manage partitions on a disk.

  $ sudo fdisk -l # list partitions
  
  $ sudo fdisk -l | sed -e '/Disk \/dev\/loop/,+5d'   # ignore Snap loop mounts

== df ==
  $ df -T  # disk filesystem format type
  
  $ df -H | grep -v ^/dev/loop   # ignore Snap loop mounts


== Note on Snap Loop Mounts ==
In addition to listing disks and partitions, fdisk and df also list loop mounts. A loop mount looks like a disk but is in fact a file containing a file system, created by a Snap package install.
The Snap package system is proprietary to Canonical.
It is deeply embedded into Canonical's Ubuntu and therefore should not be uninstalled from Ubuntu.
But I uninstalled it anyway according to https://haydenjames.io/remove-snap-ubuntu-22-04-lts/


== du ==
  $ du pub # number of blocks for all subdirectories, summary total at end
  $ du -a pub # all files, as well as subdirectories
  $ du -s pub # summary total only
  $ du -h pub # human-readable number of bytes
  $ du --exclude="*.txt" pub # shell pattern, not regexp
  $ du -d 1 pub # depth, 0 is same as -s
  $ du -a pub | sort -n -r | head -n 20 # find largest files

===== Mount =====
Use the mount command to attach (mount) file systems and removable devices such as USB flash drives at a particular mount point in the directory tree.

  $ mount                          # with no parameters, list mounted filesystems
  $ mount /dev/sda1 /media/john    # mount a partition device to a mount point
  $ sudo mount /dev/sdb1 /mnt/media
  $ unmount device_name
  $ unmount mount_point

== device name vs mount point == 
Both exist in the directory tree.  

device name is /dev/sda1, for example.

Mount point is a directory which you create.  For example:
  * /media/seagate
  * /mnt/stick128

===== Mount External USB Drive at Boot =====

  $ lsusb        # list USB devices
  $ sudo blkid   # list UUID of all block devices
  # add line to /etc/fstab:
  # UUID=4078159978158F32  /media/seagate  ntfs  auto,nosuid,nodev,nofail,x-gvfs-show  0  0 
  $ sudo mount -a # test the changes to /etc/fstab. Error can cause boot failure.
  $ sudo systemctl reboot

/dev/sda  is a disk  \\
/dev/sda1 is a partition on the disk

We mount partitions, not disks.

== tar ==
  $ tar -czvf name-of-archive.tar.gz /path/to/directory-or-file
  $ tar -xvzf name-of-archive.tar.gz