Journalling Flash File System

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Revision as of 01:55, 15 February 2007

The Journalling Flash File System (JFFS) allows you to have a writable Linux File System on a DD-WRT enabled router. It is used to store user programs like Ipkg and data into otherwise inaccessible flash memory. This allows you to save custom configuration files, host custom Web pages stored on the router and many other things not capable without JFFS.
Since the WRT54G and other models contain too little memory(4MB), it is not usefull to activate normal jffs within them.
As you might need the /jffs directory, take a look at /jffs with little flash.

If you really need or want to use JFFS with a WRT54G you have to first enable JFFS under the Administration page,
and either:

  • use mini firmware on WRT54G (still doesn't leave much room...)
  • get a WRT54GS with bigger flash (not much more expensive than WRT54G but gives quite a bit of room, 14MB free with VoIP) (in the WRT54GSv4 they have changed the memory sizes to the WRT54G sizes)
  • Non-JFFS: do the the SD card mod (unlimited room using swapped multiple SD cards, but it's a really ugly and utterly nasty hack)
    * Non JFFS, but an alternative would be to go into setup and mount a samba share. Look at this for info on how. If you are a Linux newbie look at this other


JFFS with Flash

Given you use the mini-version or have more than 4MB of flash you can activate jffs. Take care, that inspite of general purpose read/write not to store frequently changed files on it as this can cause flash wear out. Journal file is used to minimize frequent overwrites.

Enter the following commands (when you're connected via ssh or telnet on a shell):

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

might reboot/hang after cleaning which might take long, so be patient

Maybe the options in the webinterface below work for you (they didn't for me):

JFFS2 enabled: X Enable Disable
Clean JFFS2: X Enable Disable

To unmount the jffs(in case it was too small :-):

nvram set sys_enable_jffs2=0
nvram set sys_clean_jffs2=0
nvram set jffs_mounted=0
nvram commit

Afterwards you can nvram unset this variables.


Log in and run:
ipkg update
ipkg list

/jffs with little flash

If you have too little flash memory but need some memory under /jffs you can use Samba and mount the share under /jffs

To mount the samba share under /jffs you can either

  • Use a Startup Script
  • Use Samba Startup Scripts

NOTE: Even though you are not using the jffs partition on the router, you must still have jffs enabled in order to use ipkg. Disabling jffs also disables ipkg! See further instructions.

NOTE 2: You might not be able to use symbolic links when using windows-hosts. Rename(mv) could work.

Use a Startup Script

Read first, howto use Startup Scripts. Then place the following into your startup script to mount the jffs partition:

umount /jffs
smbmount //<server's IP>/jffs /jffs -o username=<your username>,password=<your password>
  • NOTE: username is guest if hosted on windows

Use Samba Startup Scripts

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.

Now here are instruction on how to do so:

1) disable jffs in the webgui if you had enabled it
2) enable samba (see also Jffs_sharing_in_a_Linux_server).

3) create a script called "" on the share:


#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

#where to log what is happening
export SMBLOG=/tmp/smblog

####### ok, here we go... ;) #######
echo "" > $SMBLOG
cd /

#make sure jffs is unmounted. Its recommended to run without jffs enabled though.
echo "umounting /jffs if nescessary..." >> $SMBLOG
umount /jffs >> $SMBLOG 2>&1

#mount our smbshare at /jffs
echo "mounting $SMBSHARE at /jffs..." >> $SMBLOG
smbmount $SMBSHARE /jffs -o username=$SMBUSER,password=$SMBPASS >> $SMBLOG 2>&1

#hand over startup to the jffs part
/jffs/$JFFS_SCRIPT & >> $SMBLOG 2>&1

4) create a script called "" on the share:


#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 enable jffs
nvram set sys_enable_jffs2=1

#ready to do specific stuff, like starting services
#or other commands from /jffs

5) in the webinterface, enable Samba with appropriate share/user/pass settings from step 2. Enter "" as the script
6) reboot

Now you should have the share configured in the webinterface 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
  • BONUS NOTE OF HAPPINESS: You need to save the script files in UNIX format, not DOS. One text editor that can do this is UltraEdit. Or Crimson Editor, which is free :o)

Use Samba Startup Scripts (Alternative Method)

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 another computer/server


  1. Enable JFFS
  2. Enable Samba
  3. Create a shell script in the Samba share, as follows:

umount /jffs
smbmount //<server's IP>/<jffs share name> /jffs -o username=<your username>,password=<your password>

  4. Enter the name of the script in the Samba startup script box in the GUI
  5. Reboot

As an example, my DD-WRT has these shares:

  • /tmp/smbshare located in a shared folder on my NAS called ddwrt, which contains scripts (including 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