[SOLVED] Question: SysRescueCD boot options

haertig · 09-03-2013, 04:01 PM

I want to ceate a slightly customized version of SysRescueCD that always sets the root password to something I previously specified every time it boots from the CD. I know about adding the "rootpass" boot option manually when booting from CD, but what I want is for the password to be set by default (hardcoded onto the CD) without any manual boot option editing required.

Actually, I want to add the following boot options permanently: rootpass=1234 docache dodhcp

( dodhcp is probably there by default already )

I cannot find in the SysRescueCD documentation where exactly I would do this. I am guessing that I will need to loop mount the iso image and copy all the files to a location on my harddrive, then edit some config file (where?) to add my desired boot options. Then create a new iso from the edited stuff and burn it. I have snooped around on a SysRescueCD image and found isolinux.cfg, isolinux.old and grub-371.cfg thus far. All of those look like potentials for editing. Each has multiple boot choices, so I'd potentially have to add my custom boot options in multiple places in multiple files. Is there a better way?

I will also be adding an auto-update for a DDNS entry every time the CD boots, but I already know how to do that via "autorun" scripting.

What I am creating here is a type of rescue disk for use by a computer illiterate. They boot with this CD, and then I get their IP address from the known DDNS entry and ssh into their box using the root password I hardcoded via boot options. Then I can fix whatever I need to for them once I have ssh access.

jailbait · 09-03-2013, 05:59 PM

"edit some config file (where?) to add my desired boot options."

I think that you pass the boot parameters as parameters on the linux command given to syslinux. syslinux uses the file syslinux.cfg to determine what linux to boot and what parameters to pass to linux. Here is an explanation of how to do that:

http://www.syslinux.org/wiki/index.p...re_SYSLINUX.3F

------------------------
Steve Stites

yancek · 09-03-2013, 06:54 PM

Quote:

I am guessing that I will need to loop mount the iso image and copy all the files to a location on my harddrive, then edit some config file (where?) to add my desired boot options.

That's pretty much it. Create a mount point for the SystemRescueCD, loop mount it there, create another directory (in your /home/user) and copy all the directories/files there. Make sure you have read/write and/or ownnership. On the version of systemrescuecd I have, the file to be modified would be the isolinux.cfg file, probably the same for yours. Take a look at the file and compare it to what you see when you boot it. You should see three lines for each menu entry, Linux, INTIRD and APPEND. Note the boot options are all on the APPEND line. That's where I would add them. You would then need to run the mkisofs command on the directory to which you copied all the directories/files in your /home/user directory. Make sure you unmount the loop mounted filesystem.

I imagine you could boot the CD and manually enter the commands a hundred or more times in the time it takes to do this, but...
If that's not what you are looking for, post back.

haertig · 09-05-2013, 03:30 PM

(1) Mounted the original ISO to a mountpoint

Code:

mkdir mountpoint
mount -o loop ./systemrescuecd-x86-3.7.1.iso ./mountpoint

(2) Copied all directory structure and files from this mountpoint to a new directory structure

Code:

mkdir ./new_structure
cd ./mountpoint
cp -av * ../new_structure/.

(3) In the copied structure, edited isolinux/isolinux.cfg to add the boot options I wanted:

isolinux.cfg before editing:

Code:

...
TIMEOUT 900
...
LABEL rescuecd_std
MENU LABEL 1) SystemRescueCd: default boot options
KERNEL ifcpu64.c32
APPEND rescue64 scandelay=1 -- rescue32 scandelay=1
TEXT HELP
Boot standard kernel with default options (should always work). You should
use this entry if you don't know which one to use. You can press [TAB] and
add extra boot options after rescue32 or/and rescue64 if required
ENDTEXT
...

isolinux.cfg after editing:

Code:

...
TIMEOUT 50
...
LABEL rescuecd_std
MENU LABEL 1) SystemRescueCd: default boot options
KERNEL ifcpu64.c32
APPEND rescue64 scandelay=1 rootpass=the_new_password setkmap=us dodhcp docache ar_ignorefail ar_nowait -- rescue32 scandelay=1 rootpass=the_new_password setkmap=us dodhcp docache ar_ignorefail ar_nowait
TEXT HELP
Boot standard kernel with default options (should always work). You should
use this entry if you don't know which one to use. You can press [TAB] and
add extra boot options after rescue32 or/and rescue64 if required
ENDTEXT
...

(4) At the root of the copied directory structure, created a new file named "autorun":

Code:

#!/bin/bash

# You must create your "DOMAIN" manually on the freedns website, http://freedns.afraid.org
DOMAIN='my_domain_name.anydns.com'
NAME_SERVER='ns1.afraid.org'
CHECK_URL='http://freedns.afraid.org/dynamic/check.php'

# You must get the "UPDATE_URL" specific for your "DOMAIN" from the freedns website
UPDATE_URL='http://freedns.afraid.org/dynamic/update.php?jhH7*%^JRdik*67VjrLKJ.<Iugy%oKJB:jlhh9y6io75vRGoYB[piJ;IJ_(*y806Ot65lL&ll'

current_ip=`wget -q -O - $CHECK_URL | grep Detected | sed s/[^0-9.]//g`
registered_ip=`nslookup $DOMAIN $NAME_SERVER | tail -2 | grep Address | sed s/[^0-9.]//g`

if [ "$registered_ip" == "" -o "$current_ip" == "" -o "$registered_ip" != "$current_ip" ]
then
	wget -q -O /dev/null "$UPDATE_URL"
fi

cat > /usr/bin/checkip <<EOF
#!/bin/bash
wget -q -O - $CHECK_URL | grep Detected | sed s/[^0-9.]//g
EOF
chmod 555 /usr/bin/checkip

cat > /usr/bin/checkdns <<EOF
#!/bin/bash
nslookup $DOMAIN $NAME_SERVER | tail -2 | grep Address | sed s/[^0-9.]//g
EOF
chmod 555 /usr/bin/checkdns

cat > /usr/bin/updatedns <<EOF
#!/bin/bash
wget -q -O /dev/null "$UPDATE_URL"
EOF
chmod 555 /usr/bin/updatedns

exit 0

5) Made the new autorun file executable ("chmod 555 ./autorun")

6) Created a new ISO image from the copied/modified directory structure:

Code:

mkisofs -o /tmp/custom_sysrescuecd.iso \
        -b isolinux/isolinux.bin \
        -c isolinux/boot.cat \
        -no-emul-boot \
        -boot-load-size 4 \
        -boot-info-table \
        -J \
        -R \
        -V custom_sysrescuecd \
        .

7) Burned the new ISO to a CD (I used Brasero, but could have done it from the commandline using cdrecord, wodim, etc.)