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Moxa EM-1220-LX [29/57] Journaling flash file system jffs2
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EM-1240-LX User’s Manual Software Package
Flash Context Flash Address Size Access control
Boot loader 0 – 0x3ffff 256 K Read ONLY
Kernet &
Root File System
0x40000– 0x3fffff 4 M Read ONLY
JFFS2
User Directory 0x400000 – 0x7fffff 4 M – 256 K Read / Write
JFFS2
Developers should store their own programs only to partitions /etc, /home, /tmp, and /usr/bin. In
addition, executable files should be stored in /usr/bin, as doing so will allow developers to use
hotkeys.
In addition to the flash file systems, a RAM based file system is mounted on /var/.
Journaling Flash File System (JFFS2)
The flash User Directory is formatted by the Journaling Flash File System (JFFS2), which places a
compressed file system on the flash, transparent to the user.
Axis Communications in Sweden developed the Journaling Flash File System (JFFS2).
JFFS2 provides a file system directly on flash, rather than emulating a block device designed for
use on flash-ROM chips. It recognizes flash-ROM chips’ special write requirements, does
wear-leveling to extend flash life, keeps the flash directory structure in RAM at all times, and
implements a log-structured file system that is always consistent—even if the system crashes or
unexpectedly powers down. It does not require fsck on boot up.
JFFS2, a later version of JFFS, 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 (thus enhancing the write-life of the devices), native data compression
inside the file system design; and support for hard links.
Key features of JFFS2 are:
y Directly targeted to Flash ROM
y Robust
y Consistent across power failure
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. Any writes that were already completed will not be affected.
Additional information about JFFS2 is available at
http://sources.redhat.com/jffs2/jffs2.pdf
http://developer.axis.com/software/jffs/
http://www.linux-mtd.infradead.org/
3-3
Содержание
- Em 1240 lx user s manual 1
- Fifth edition february 2009 1
- Www moxa com product 1
- Copyright notice 2
- Disclaimer 2
- Em 1240 lx user s manual 2
- Technical support contact information www moxa com support 2
- Trademarks 2
- Table of contents 3
- Introduction 5
- Overview 6
- Package checklist 6
- Product features 6
- Hardware specifications 7
- Product specifications 7
- Software specifications 8
- Appearance 9
- Em 1240 embedded module development kit 9
- Em 1240 lx user s manual introduction 9
- Hardware block diagram 9
- Em 1240 development kit 10
- Em 1240 embedded module 10
- Em 1240 lx user s manual introduction 10
- Dimensions 11
- Installing the em 1240 lx 11
- Led indicators 12
- Wiring requirements 12
- Connecting data transmission cables 13
- Connecting the power 13
- Connecting to the network 13
- Grounding the em 1240 lx 13
- Connecting to a serial device 14
- Serial console port 14
- Additional functions 15
- Internal sd socket 15
- Reset button 15
- Real time clock 16
- Getting started 17
- Connecting the em 1240 lx to a pc 18
- Console port 18
- Powering on the em 1240 lx 18
- Telnet 19
- Configuring the ethernet interface 20
- Developing your applications 22
- Installing a secure digital sd memory card 22
- Compiling hello c 23
- Installing the em 1240 lx tool chain 23
- Uploading hello to the em 1240 lx 24
- Running hello on the em 1240 lx 25
- Make file example code 26
- Software package 27
- Em 1240 lx software architecture 28
- Journaling flash file system jffs2 29
- Em 1240 lx software package 30
- Configuring the em 1240 lx 32
- Enabling and disabling daemons 33
- How to enable disable etc inittab www server 33
- How to enable disable telnet ftp server 33
- How to enable network time protocol 33
- How to update the system time periodically with network time protocol 33
- Adding a web page 34
- Iptables 34
- Observe and erase chain rules 36
- Append or delete rules 37
- Define policy for chain rules 37
- Enabling nat at bootup 38
- Nat example 38
- Configuring dial in dial out service 39
- Configuring pppoe 39
- Connect using a modem 39
- Dial in service 39
- Dial out service 39
- Direct cable connection 39
- Dynamic driver module load unload 40
- How to mount a remote nfs server 40
- Upgrading the kernel 41
- Upgrading the root file system user directory 42
- Autostarting user applications on bootup 43
- Checking the kernel and root file system versions 43
- Loading factory defaults 43
- Em 1240 lx device api 44
- Buzzer 45
- Rtc real time clock 45
- Uart interface 45
- Api list 46
- Moxa gpio api 46
- How to use the gpio 47
- Gpio library source code 48
- Limits 48
- A system commands 52
- Editor 52
- File manager 52
- System commands 52
- Μclinux normal command utility collection 52
- Moxa special utilities 53
- Network 53
- Process 53
- B snmp agent with mib ii rs 232 like group 54
- Snmp agent with mib ii rs 232 like group 54
- C em 1240 lx faq 57
- Em 1240 lx faq 57
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