File System Hierarchy Standard (FHS) Defines standard locations for temporary files on Linux systems

• /tmp - is recommended to be cleared between boot session and material is not guarenteed to be retained
• /var/tmp should not be cleared during system boot up as they will persist between boots
• /run contains run-time variable data used by running processes (example .pid). This must be cleared during system boot-up time
• permissions can be a challenge with permissions and sticky bits are ignored on files by the Linux kernel
• Symbolic link - soft links that point to the path of another file
  • if the file is deleted or moved, the link points stop working
• Hard Links - hard links point to the inode on the disk
  • inode is a data structure that stores attributes for an object on a file system
    • includes file permissions, name, ownership, and where on the disk block the data for the object is stored (inode aka index node)
• ln command makes hard links (and soft when using -s)
  • the target must already exist (the file the link will point to)
  • full path must be specified if it is not on the current directory
  • every hard link pointing to a file increases the link count of the file. This is a number found between the permissions (rwxrwxrwx) and the name of the user and group
  • rm and mv can be used to move and delete hard links as they are treated like any file even though they are technically not a duplicate. They will not break from being moved

The information for hard link counts, permissions…etc can be found using the ls -li command

• ln -s command is used to make soft links for files and directories
• soft links are easier to spot as when seen in ls -lh command, it distinctly indicates softlink →
• soft links can have issues when being moved unless the path is fully specified, it is seen as a relative to the location of the link (say if you are moving it out of the current directory it was in and it was set based on that directory)

D281 - Linux Essentials