TechInfoDepot:DD-WRT/Journalling Flash File System
Journalling Flash File System @ dd-wrt
Introduction
Journalling Flash File System (JFFS/JFFS2) is a re-writable area within a DD-WRT-enabled device.
- Located in /jffs.
Contents stored:
- On DD-WRT Device main flash directly on the device (/jffs), or
- mount --bind /storagelocation /jffs.
Where storagelocation is- Off-board supplemental flash, see SD/MMC mod, (/mmc/jffs).
- Network Area Storage [NAS], or Server. (//servername/sharename)
- JFFS reports as it's own free space, the free space on Share or SD Card, in the Web Interface
Examples of the kind of programs and data are:
- Custom configuration files
- NoCat splash pages and configuration
- ipkg (Requires JFFS. See ipkg.)
- Web-site hosting
- Many other things.
- JFFS must be Enabled for certain /jffs-dependent applications.
Enable JFFS: Create /jffs
Prerequisites
To enable JFFS you will need a router with at least 4MB flash, a build that supports JFFS such as the Mini build which is the smallest build to support JFFS thus leaving the most space for the JFFS partition, and your build must leave at least 324KB of flash free for the JFFS file system structure which will not be usable space. v24 pre-SP2 Standard builds no longer leave enough space for JFFS on 4MB devices so use the Mini build or one of Eko's specialty builds.
Very old versions of some Linksys routers (no longer manufactured for many years) contained 8MB of Flash and 32MB of RAM, many DD-WRT-capable devices today contain 4MB of Flash memory; a few models from certain manufacturers contain more flash (La Fonera, ASUS WL-500GP), some contain less (2MB). See Supported Devices.
Note that DD-WRT v24sp1 VPN builds have the JFFS feature removed, presumably due to conflicts that Brainslayer found between JFFS and bandwidth monitoring. See this thread for more information. Users interested in v24sp2 can opt:
- Use a build other than VPN, both MINI and MEGA still have JFFS
- Use an older build of DD-WRT
- Use a custom build, either homemade or dd-wrt.v24-10086_NEWD_openvpn_jffs_small.bin, which is described here as missing "snmp, all languages, some GUI styles and more.".
NOTE FOR ASUS WL500W
As of October 7th, 2009, consider the following or you may BRICK you router:
Brainslayers mega flash size - 7.33MB
Eko's Big Flash size - 5.9MB
Now, the error only occurs when JFFS2 is enabled and the router reboots, so you are safe if you DONT enable JFFS2.
Total available JFFS2 size for BS's build is 640KB which overwhelms the kernel and causes a panic. Even using a storage device with the command mount -o bind /mnt/jffs /jffs will still cause a kernel panic.
Eko's JFFS2 partition size is 1640KB+, allowing much more room.
I tested this on BS's 12996,12874 and 12533 builds and partially bricked my router several times. (A simple power disconnect for 30 secs will allow it to recover)
Eko's build however works flawlessly AND provides the SAME features (except for connection warning) as BS's.
One thing I am still unsure of is why this particular model Asus router is subject to this bug, but in the mean time, I suggest using Eko's Big build until the dev's can work it out..
Flash Wear: A Warning
Take care not to store frequently changing files (i.e. often-changing log files) on Flash as this can cause flash wear-out over time.
- A journalling flash file system is specifically designed to minimize frequent overwrites.
- Files which are read many times but written infrequently work well on main flash.
- Using the space provided by SD/MMC mod places wear on replaceable secondary flash storage.
Directions for (normal) users: using Web-GUI Interface
The steps to enable JFFS through the router web page are very specific. To avoid having to reset and reprogram your router, it's smart to make a backup here of your settings. If you follow these steps exactly, it should not lock up.
- On the router web page click on Administration.
- Scroll down until you see JFFS2 Support section.
- Click Enable JFFS.
- Click Save.
- Wait couple seconds, then click Apply.
- Wait again. Go back to the Enable JFFS section, and enable Clean JFFS.
- Do not click "Save". Click Apply instead.
The router formats the available space. - Wait till you get the web-GUI back, then disable "Clean JFFS" again.
- Click "Save".
- It may be wise to Reboot the router, just to make sure
Directions for (freaky) Linux Gurus: CLI
WARNING
A user comments: I tried the following commands under La Fonera firmware v24 RC4 and corrupted all my settings. I had to recover my unit with the procedures on La Fonera flashing page. I am not sure if this is a bug or these commands are not suited for La Fonera. Please try to use the web interface above. It works for me.
Enter the following commands from the CLI:
nvram set jffs_mounted=1 nvram set enable_jffs2=1 nvram set sys_enable_jffs2=1 nvram set clean_jffs2=1 nvram set sys_clean_jffs2=1 nvram commit reboot
Note: Device might reboot/hang after cleaning which might take long; be patient.
To unmount the JFFS:
nvram set sys_enable_jffs2=0 nvram set sys_clean_jffs2=0 nvram set jffs_mounted=0 nvram commit reboot
Afterwards you can delete these variables with "nvram unset <variable>".
Options for Increasing JFFS Space
Add a 1GB flash memory card
- Add the SD/MMC mod
- up to (at least) 1GB storage using common swappable SD memory cards (built-in support with DD-WRT v2.4 and later).
- create the folder /mmc/jffs
- mkdir /mmc/jffs
- Use the Mount Bind command to point /jffs to the storage card:
- mount --bind /mmc/jffs /jffs
- with v24 enable JFFS2 support (tab: Administration -> tab: Management -> section: JFFS2 Support)
- or command nvram set sys_enable_jffs2=1
- To use ipkg also create folder /jffs/tmp/ipkg
- mkdir /jffs/tmp
- mkdir /jffs/tmp/ipkg
- For Windows: WinSCP can be used to transfer files to and from the router, eliminating the need to pull the card out and put it in a card reader on a PC.
- For Linux, Mac OS X: Other SCP transfer applications exist.
- Removed cards can be accessed natively in Linux or OS X, or on Windows with the Ext2FS driver ([1] or [2]).
- On older firmware (v2.3), the limited JFFS space can be used to hold the drivers to load support for the SD card.
Add USB Storage
- Routers with USB storage like Linksys WRTSL54GS or ASUS WL-500g Premium can have firmware with built-in USB support and then /jffs mounted on the USB device. To enable USB on these devices see: USB storage
- V24 and later firmware: USB support is available within Mega and some Mini builds.
- Using V24SP1 Mega on an Asus WL-500W with external USB HDD:
- To mount the USB drive, and enable /jffs
mount /dev/scsi/host0/bus0/target0/lun0/part1 /mnt mkdir /mnt/jffs mount /mnt/jffs /jffs
- Also enable JFFS2 support in either web-GUI (tab: Administration -> tab: Management -> section: JFFS2 Support)
- or with the command
nvram set sys_enable_jffs2=1
- To use ipkg also create folder /jffs/tmp/ipkg
mkdir /jffs/tmp mkdir /jffs/tmp/ipkg
Using CIFS (Client Samba): Storing /jffs content remotely
One option is to create a share on the network and mount it on the router at /jffs using CIFS. Exact steps at CIFS
Overview:
- Enable JFFS in the web-GUI or put the following command in a Script or Startup Command.
nvram set sys_enable_jffs2=1
- Create a share on a CIFS-capable server called jffs.
- Standard Microsoft Windows Shared Folder
- Other operating systems may refer to SMB or Samba
- In the Web GUI mount the CIFS share at /jffs.
- Folder /jffs appears locally, while
- Content actually saved remotely, on
- NAS (Network Attached Storage)
- Server (PC or some type of file server)
- To use ipkg also create folder /jffs/tmp/ipkg
- mkdir /jffs/tmp
- mkdir /jffs/tmp/ipkg
Costs:
- ! Setting up a NAS or Server only for router maybe not economical.
- Equipment Costs: Requires existing NAS or PC Server
- Electricity Costs: if entire Server is only serving router
- Availability Demands: CIFS share must be available
- 24/7, or whenever the DD-WRT Device is on, and
- Storing JFFS Share on quality equipment is required (i.e. Raid, Power Backup)
- ! Remote storage down means /jffs down, could mean DD-WRT Device down (increases the weak points).
- Security Limitations: CIFS is limited to Microsoft's SMB protocol, offering up to only 128-bit security.
- Poor Microsoft Protocol Security is not a problem if the LAN is physically and electronically protected from outside or inside intrusion (i.e. Guards, Guns, Locks, Dogs, Mines, Cameras, Firewalls)
- LAN Connection Required: NAS cannot be wirelessly attached to DD-WRT Device.
- Hassle: Using Microsoft Windows as the jffs Server
- ! Symbolic links in /jffs may not work.
- ! Rename (mv) commands on the /jffs mount may not work.
Most people only own an (inexpensive) Windows PC. A common Desktop PC does not a 24/7 Server make.
The following non-updated (as of 20080520) examples may be out of date:
- CIFS was broken on many builds this update author tried. Although other people have reported it working - It may be a limitation of BusyBox CIFS when using NTLMv2 and 128-bit encryption.
- (Mostly) only structural and spelling mistakes were corrected below (20080522)
Use a Startup Script: Example 1
- Read how to use Startup Scripts. Then place the following into your startup script to mount the JFFS partition:
umount /jffs #unmounts existing /jffs if existing mount.cifs //<server's IP>/jffs /jffs -o username=<the username>,password=<the password> nvram set sys_enable_jffs2=1 # fake-enable JFFS. Enable but do not commit. Makes ipkg think jffs2 is enabled.
NOTE: Username is Guest when hosted on Windows XP & 'Simple File Sharing' is enabled - This is the default on Windows XP Home.
Use Startup Scripts: Example 2
This method uses 2 scripts: The first will be started from /tmp/smbshare & mount the samba share under /jffs and start the other script. The second will be started from /jffs and unmount /tmp/sambashare.
Instructions:
- Enable CIFS (see also Jffs sharing in a Linux server).
- Create a script called "startup.smb.sh" on the share:
#!/bin/sh #smb settings: same as the settings in the webgui # change these to mount a different share than the current at /jffs SMBSHARE=`nvram get samba_share` SMBUSER=`nvram get samba_user` SMBPASS=`nvram get samba_password` #script to start in /jffs once we're done mounting JFFS_SCRIPT=startup.jffs.sh #where to log what is happening export SMBLOG=/tmp/smblog ####### ok, here we go... ;) ####### echo "" > $SMBLOG cd / #make sure JFFS is unmounted. echo "umounting /jffs if necessary..." >> $SMBLOG umount /jffs >> $SMBLOG 2>&1 #mount our smbshare at /jffs echo "mounting $SMBSHARE at /jffs..." >> $SMBLOG mount.cifs $SMBSHARE /jffs -o username=$SMBUSER,password=$SMBPASS >> $SMBLOG 2>&1 #hand over startup to the JFFS part /jffs/$JFFS_SCRIPT & >> $SMBLOG 2>&1
4. create a script called "startup.jffs.sh" on the share:
#!/bin/sh #wait a sec, just to be sure the smb startup script has quit sleep 1 #unmount the smbshare, its identical to /jffs now anyway :) umount /tmp/smbshare #to enable ipkg, we fake JFFS enabled. #since theres no commit, this wont actually create a /jffs at Startup. nvram set sys_enable_jffs2=1 #ready to do specific stuff, like starting services #or other commands from /jffs
5. in the webinterface, enable CIFS with appropriate share/user/pass settings from step 2.
- Enter "startup.smb.sh" as the script
6. Apply Changes
7. reboot
Now you should have the share configured in the web interface mounted at /jffs and should also be able to run 'ipkg' !
- NOTE: If you are a Linux newbie, and you have problems with file permissions, look at this
- Script files must be saved in UNIX format, not DOS. Windows editors that can do this are UltraEdit. EditPadPro and Crimson Editor, are free.
- WinSCP can be used to easily change the execute flags on the scripts.
Use Startup Script: Example 3
This method requires 2 shares available for DD-WRT, but allows you to have 2 different areas of storage for the router. Some might find it useful. It is an amalgamation of the previous 2 methods.
Things you need:
- 2 writeable shares on an NAS or Server.
Procedure:
1. Enable CIFS
2. Create a shell script in the network share, as follows:
#!/bin/sh nvram set sys_enable_jffs2=1 # fake-enable JFFS umount /jffs # unmount /jffs if it exists mount.cifs //<server's IP>/<jffs share name> /jffs -o username=<your username>,password=<your password>
3. Enter the name of the script in the CIFS-Samba startup script box in the Web Interface.
4. Apply changes.
5. Reboot
As an example network setup:
- /tmp/smbshare located in a shared folder on the NAS called ddwrt, which contains scripts (including startup.sh containing the above commands), yet to be installed packages and other static data
- /jffs located in a shared folder called jffs, which contains program data for installed packages
Testing ipkg
Log in to the CLI (via Telnet or SSH) and enter the following commands:
cd /jffs mkdir -p /jffs/tmp/ipkg ipkg update ipkg list
It is recommended that you reboot the router after running the above commands.
