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What do you know about /var?


/var:
  1.  It is a standard sub-directory of the root directory in Linux and other Unix-like operating systems that contains files to which the system writes data during the course of its operation.
  2. It contains variable data like system logging files, mail and printer spool directories.
  3. Some portions of /var are not shareable between different systems. For instance, /var/log, /var/lock, and /var/run. Other portions may be shared, notably /var/mail, /var/cache/man, /var/cache/fonts, and /var/spool/news.  
  4. It contains a number of sub-directory. These sub-directories is designated by a forward slash (/). Among the other directories that are usually installed by default in the root directory are /bin, /boot, /dev, /etc, /home, /initrd, /lib, /lost+found, /misc, /mnt, /opt, /proc, /root, /sbin, /tmp ,/local, /log, /mail, and /usr....etc
  5. Its contents are not included in /usr because situations can occur in which it is desired to mount /usr as read-only, such as when it is on a CDROM or on another computer. /usr, which is generally the largest directory (at least on a newly installed system) and is used to store application programs, should only contain static data.
  6.  Explanation of some sub-directories:
    1. /var/cache (contains cached data from application programs).
    2.  /var/games (contains variable data relating to games in /usr).
    3.  /var/lib (contains dynamic data libraries and files).  
    4. /var/lock (contains lock files created by programs to indicate that they are using a particular file or device).  
    5. /var/log (contains log files).  
    6. /var/run (contains PIDs and other system information that is valid until the system is booted again).
    7. /var/spool (contains mail, news and printer queues). 
read more.

References:
  1. http://www.linfo.org/var.html 
  2. http://www.tldp.org/LDP/Linux-Filesystem-Hierarchy/html/var.html

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