README
======
Overview
--------
This directory contains logic to support a custom ROMFS start-up script.
This startup script is used by by the NSH when it starts provided that
CONFIG_NSH_ARCHROMFS=y. The script provides a ROMFS volue that will be
mounted at /etc and will look like this at run-time:
NuttShell (NSH) NuttX-7.31
MOTD: username=admin password=Administrator
nsh> ls -Rl /etc
/etc:
dr-xr-xr-x 0 .
-r--r--r-- 20 group
dr-xr-xr-x 0 init.d/
-r--r--r-- 35 passwd
/etc/init.d:
dr-xr-xr-x 0 ..
-r--r--r-- 110 rcS
nsh>
/etc/init.d/rcS is the start-up script; /etc/passwd is a the password
file. It supports a single user:
USERNAME: admin
PASSWORD: Adminstrator
nsh> cat /etc/passwd
admin:8Tv+Hbmr3pLddSjtzL0kwC:0:0:/
The encrypted passwords in the provided passwd file are only valid if the
TEA key is set to: 012345678 9abcdef0 012345678 9abcdef0. Changes to either
the key or the password word will require regeneration of the nsh_romfimg.h
header file.
The format of the password file is:
user:x:uid:gid:home
Where:
user: User name
x: Encrypted password
uid: User ID (0 for now)
gid: Group ID (0 for now)
home: Login directory (/ for now)
/etc/group is a group file. It is not currently used.
nsh> cat /etc/group
root:*:0:root,admin
The format of the group file is:
group:x:gid:users
Where:
group: The group name
x: Group password
gid: Group ID
users: A comma separated list of members of the group
Updating the ROMFS File System
------------------------------
The content on the nsh_romfsimg.h header file is generated from a sample
directory structure. That directory structure is contained in the binary
file etc.tar.gz and can be modified per the following steps:
NOTE: It is not advised to do this under Windows. Windows will end up
changing the file permissions so the files under /etc will have executable
permissions.
1. Unpack the directory structure:
tar zxf etc.tar.gz
2. Make modifications as desired.
3. Create the new ROMFS image.
genromfs -f romfs_img -d etc -V SimEtcVol
4. Convert the ROMFS image to a C header file
xxd -i romfs_img >nsh_romfsimg.h
5. Edit nsh_romfsimg.h, mark both data definitions as 'const' so that
that will be stored in FLASH.
6. Re-package the modified /etc directory
tar cvf etc.tar etc
gzip etc.tar
See the sim/nsh configuration for an example of the use of this file
system.
Replacing the Password File
---------------------------
The sim/nsh configuration can also be used to create a new password file.
First, make these configuration changes:
1. Disable logins
- CONFIG_NSH_CONSOLE_LOGIN=y
+ # CONFIG_NSH_CONSOLE_LOGIN is not set
# CONFIG_NSH_TELNET_LOGIN is not set
2. Move the password file to a write-able file system:
- CONFIG_FSUTILS_PASSWD_PATH="/etc/passwd"
+ CONFIG_FSUTILS_PASSWD_PATH="/tmp/passwd"
3. make the password file modifiable
- CONFIG_FSUTILS_PASSWD_READONLY=y
# CONFIG_FSUTILS_PASSWD_READONLY is not set
Now rebuild the simulation. No login should be required to enter the
shell and you should find the 'useradd', 'userdel', and 'passwd' commands
available in the help summary, provided that they are enabled. Make
certain that the 'useradd' command is not disabled:
# CONFIG_NSH_DISABLE_USERADD is not set
Use the NSH 'useradd' command to add new uses with new user passwords like:
nsh> useradd <username> <password>
Do this as many times as you would like. Each time that you do this a new
entry with an encrypted password will be added to the passwd file at
/tmp/passwd. You can see the passwd file like:
nsh> cat /tmp/passwd
When you are finished, you can simply copy the /tmp/passwd content from the
'cat' command and paste it into an editor. Make sure to remove any
carriage returns that may have ended up on the file if you are using
Windows.
Then recreate the nsh_romfsimg.h file as described above. In step 2,
simply replace the old /etc/passwd file with the one in your editor.
When you are finished, the new passwd file will be in the ROMFS file
system at the path /etc/passwd. When you restore the original NSH
sim configuration, these are the passwords that will be used.
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