Filesystem

• man hier shows us a description of the Linux filesystem hierarchy.

• Despite multiple directories and mount points being used, they are all part of the same filesystem.

• The config for how the different drive partitions are mounted can be found in /etc/fstab.

• mount can be used to mount partitions at different mount points on filesystem.

• df displays disk filesystem space usage of all mounted partitions, and du displays disk usage of files & directories on disk.

• Absolute paths always start from the root of the filesystem and ignore current working directory; relative paths are paths from current working directory.

• ls -l file.txt shows the last modification time of a file; to update the modification time, we can run touch file.txt - but this will create the file if it does not exist.

• For filename with spaces, we can either escape the space character like cat file\ name.txt, or place the enter name in quotes like cat "file name.txt".

• Globbing examples:

  • ls file*.txt - matches text files starting with 'file'

  • ls file?.txt - matches text files starting with 'file' and having another character after that

  • ls **/*.txt - matches text files across directories

  • ls file[123].txt - matches text files starting with 'file' and having '1', '2', or '3' after that

  • ls file[a-zA-Z].txt - matches text files starting with 'file' and having any of the letters in the provided range after that

• ln can be used to create hard and soft links:

  • Hard link points to physical location of file on storage - ln hello.txt hello-hardlink.txt creates a hard link for 'hello.txt'.

  • Changes in original file will follow in hard link - original file can be deleted, but hard link still persists.

  • Soft (symbolic) link references file or directory on filesystem - ln -s hello.txt hello-softlink.txt creates a soft link.

  • If the resource is removed from filesystem, the soft link will not work.

• Compressing & archiving files:

  • zip tmp/backup.zip f1.txt f2.txt f3.txt - creates zip file

  • unzip -l tmp/backup.zip - lists contents of zip file

  • zip -r tmp/backup-dir.zip dir1 dir2 - creates zip file of directory contents

  • tar cvf backup.tar file?.txt dir? - archives files and directories matching the format

  • tar tvf backup.tar - lists contents of archive

  • tar xvf backup.tar - extracts files from archive

  • gzip backup.tar - compresses archive

  • gunzip backup.tar.gz - decompresses archive

• Searching in filesystem:

  • find . -name 'file*.txt' - finds files with specific format in current & sub-directories

  • find . -iname 'file*.txt' - case-insensitive search

  • locate file.txt - searches from a database of file names from entire filesystem