Moxa Technologies W341 Manual De Usuario

 

Factory Default Image file. The user directory saves the user’s settings and application. 

To improve system reliability, the W311/321/341 have a built-in mechanism that prevents the 
system from crashing. When the Linux kernel boots up, the kernel will mount the root file system 
for read only, and then enable services and daemons. At the same time, the kernel will start 
searching for system configuration parameters via rc or inittab. 

Normally, the kernel uses the Root File System to boot up the system. The Root File System is 
protected, and cannot be changed by the user. This type of setup creates a “safe” zone. 

For more information about the memory map and programming, refer to Chapter 6, Programmer’s 
Guide. 

Journaling Flash File System (JFFS2) 

The Root File System and User directory in the flash memory is formatted with the Journaling 
Flash File System (JFFS2). The formatting process places a compressed file system in the flash 
memory. This operation is transparent to the user. 

The Journaling Flash File System (JFFS2), which was developed by Axis Communications in 
Sweden, puts a file system directly on the flash, instead of emulating a block device. It is designed 
for use on flash-ROM chips and recognizes the special write requirements of a flash-ROM chip. 
JFFS2 implements wear-leveling to extend the life of the flash disk, and stores the flash directory 
structure in the RAM. A log-structured file system is maintained at all times. The system is always 
consistent, even if it encounters crashes or improper power-downs, and does not require fsck (file 
system check) on boot-up. 

JFFS2 is the newest version of JFFS. It provides improved wear-leveling and garbage-collection 
performance, improved RAM footprint and response to system-memory pressure, improved 
concurrency and support for suspending flash erases, marking of bad sectors with continued use of 
the remaining good sectors (enhancing the write-life of the devices), native data compression 
inside the file system design, and support for hard links. 

The key features of JFFS2 are: 

y Targets the Flash ROM Directly 
y  Robustness 
y  Consistency across power failures 
y  No integrity scan (fsck) is required at boot time after normal or abnormal shutdown 
y  Explicit wear leveling 
y Transparent compression 
Although JFFS2 is a journaling file system, this does not preclude the loss of data. The file system 
will remain in a consistent state across power failures and will always be mountable. However, if 
the board is powered down during a write then the incomplete write will be rolled back on the next 
boot, but writes that have already been completed will not be affected.