There are plenty of information available online on linux command line, but I made myself a cheatsheet of things that I find using quite often.

rsync

• Mainly I use this for backing up folders on my computer to my external hard drive

  # -r for recursive
  # -v for verbose (to see printout of progress)
  rsync -rv /path/to/sync/from/ /path/to/sync/to/
      

• Archive mode also available

du, df, fdisk

• “du” returns the “disk usage” of files/directories

  # list file size of files in immediate direectory, and the subfolders 
  # (but not the files within them)
  du .
      
  # use -s (for summary) of size of directory
  du -s .
      
  # use -h (for human?) for more human-friendly file size units to be used
  du -sh .

• “df” returns disk usage of file systems

  # Summary of all file systems (-h makes the file size units more human friendly)
  df -h
      

• “fdisk” is a partition table manipulator (will likely require sudo)

  # list all partitions in system
  fdisk -l
  
  # To set partitions for hard drive, e.g sdb
  sudo fdisk /dev/sdb 
  # d to delete partition, n to add new partition
  # p primary, create, w to write changes

Formatting hard drives

• exfat should be used for more universal external drive for mac/windows/linux

• If exfat support is required, then install with:

  sudo add-apt-repository universe
  sudo apt-get update && sudo apt-get install exfat-utils

• Format partitions:

  # format partitions...the number, e.g. 1 for sdb1, 
  # is important or it will delete the partitions
  mkfs.ext4 /dev/sdb1

Mount/unmount drives

• To mount drive:

  # if sdd1 is the partition to umount
  mount /dev/sdd1 /directoryofchoice

• To unmount drive (and power off if USB):

  udisksctl unmount -b /dev/sdd1
  udisksctl power-off -b /dev/sdd

• To mount drive permanently:

  sudo vi /etc/fstab
  
  # e.g. add this line to map sdb1 to /my/directory:
  /dev/sdb1 /my/directory ext3  defaults  0  0
      
  # then exit, and run:
  sudo mount -a 
  # might need rebooting if "mount point does not exist"

Access rights

• Every file on an ext filesystem has:

  • An owner user
  • An owner group
  • Permissions for this user, this group and everybody else.

• Use chmod to modify file/folder access rights (g+s to makes any new files/folders created inside directory have same chmod rights as parent)

  chmod g+s /path/to/parent 

• If setting rwx group permissions on a file, only the owner group of that file can read/write/execute it. You can, though, change user and owner with:

  chown username file1 file2 ...
  chown -R username somedir
  chgrp groupname file1 file2 ....
  chgrp -R groupname somedir
  chown username:groupname file1 file2 ...