SunOS release 5.7 and SunOS release 4 file systems are similar, but there are changes in the locations and names of system directories and files. There are also new file systems, new pseudo file systems, and one directory is not used.
Some of the changes to file system locations and names are:
The /dev directory has changed from a flat directory to a hierarchical one.
The /etc directory contains system configuration information. Several files and subdirectories have been added, removed, or changed.
The /etc/vfstab tab file replaces /etc/fstab.
The /etc/lp directory replaces /etc/printcap.
The SunOS release 5.7 /sbin directory contains the rc scripts used to alter system run levels as well as the rcs script used to initialize the system prior to mounting file systems.
The SunOS release 5.7 /usr directory contains sharable files and executables provided by the system.
The /var directory contains files that change sizes during normal operation. Several files and subdirectories in the /var directory have been added, removed, or changed.
The /var/mail directory replaces /var/spool/mail.
The terminfo database replaces termcap.
The SunOS release 5.7 pseudo file systems are:
CACHEFS pseudo file system - can be used to improve performance of slow devices such as a CD-ROM drive.
PROCFS pseudo file system - resides in memory and contains a list of active processes, by process number, in the /proc directory. See the proc(4) man page.
FDFS pseudo file system - provides explicit names for opening files using file descriptors.
FIFOFS pseudo file system - contains pipe files that give processes common access to data.
NAMEFS pseudo file system - used mostly by STREAMS for dynamic mounts of file descriptors on top of files.
SWAPFS pseudo file system - the default swap device when the system boots, or you create additional swap space.
The following file systems are included in the SunOS release 5.7 directory structure:
The optional /opt file system, which can be used to store third-party or unbundled software. If /opt is not a separate file system, it may be a symbolic link to /usr/opt.
Support for the RFS file system type has been removed.