How to create a custom ISO image in CentOS

kickstart iso disk-image

97,018

Create a directory to mount your source.
```
mkdir /tmp/bootiso
```
Loop mount the source ISO you are modifying. (Download from Red Hat / CentOS.)
```
mount -o loop /path/to/some.iso /tmp/bootiso
```
Create a working directory for your customized media.
```
mkdir /tmp/bootisoks
```
Copy the source media to the working directory.
```
cp -r /tmp/bootiso/* /tmp/bootisoks/
```
Unmount the source ISO and remove the directory.
```
umount /tmp/bootiso && rmdir /tmp/bootiso
```
Change permissions on the working directory.
```
chmod -R u+w /tmp/bootisoks
```
Copy your Kickstart script which has been modified for the packages and %post to the working directory.
```
cp /path/to/someks.cfg /tmp/bootisoks/isolinux/ks.cfg
```

Copy any additional RPMs to the directory structure and update the metadata.

cp /path/to/*.rpm /tmp/bootisoks/Packages/.
cd /tmp/bootisoks/Packages && createrepo -dpo .. .

Add kickstart to boot options.

sed -i 's/append\ initrd\=initrd.img/append initrd=initrd.img\ ks\=cdrom:\/ks.cfg/' /tmp/bootisoks/isolinux/isolinux.cfg

Create the new ISO file.

cd /tmp/bootisoks && \ 
mkisofs -o /tmp/boot.iso -b isolinux.bin -c boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -V "CentOS 7 x86_64" -R -J -v -T isolinux/. .

(Optional) Use isohybrid if you want to dd the ISO file to a bootable USB key.
```
isohybrid /tmp/boot.iso
```
Add an MD5 checksum (to allow testing of media).
```
implantisomd5 /tmp/boot.iso
```

If you need more help creating the Kickstart script, I suggest starting with the official Red Hat documentation.

97,018

Ramesh Kumar

I am Linux freak.. :)

Updated on September 18, 2022

Comments

Ramesh Kumar almost 2 years

I am trying to create a custom ISO image which would install the minimal required RPMS along with some custom written RPM of my app. and Also wants to perform some post install steps like configuring my App and VPN configuration etc.

I saw some of the links on google but they are pointing creating repo and ISO from mounted disk or ISO image.

Thanks Ramesh
- fyarci over 8 years
  
  you can also use redhat kickstart for this job it more easier and more flexible choice More information here access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Lin‌ux/…
Ramesh Kumar almost 11 years

I got it working, but I have facing another issue, %post section does not executing any script to commands like wget, source, etc. But some of the commands are working fine, like cat(creating a new file),chmod etc.. Actually, I want to execute a bash script in %post section which will install couple of RPMS and will setup VPN and some other configurations.
Aaron Copley almost 11 years

You'll want to ask another question. This site works best with single questions and answers. Be sure to include your troubleshooting steps. (What errors are given during Kickstart?) Check the virtual consoles. (CTRL+ALT+F1 through CTRL+ALT+F5)
Aaron Copley over 9 years

Is it possible you missed or botched step 4, then?
sivann over 9 years

@AaronCopley yes, you're probably right. I also found this: github.com/joyent/mi-centos-7 which helped me.
Aaron Copley over 9 years

Hrmm.. To be fair, I have not tested this process for CentOS 7, yet. (It's been tested for 5 and 6 only.)
hshib over 9 years

On step 9, I believe you must give last parameter . (dot) to indicate current directory. Strange default behavior but without that, mkisofs creates an iso file which contains only the files from the top directory and no subdirectories and beyond.
hshib over 9 years

I also had issue with step 4. With that usage of "cp" command it does not copy the hidden files .discinfo and .treeinfo. Without those, created iso fails during the installation complaining that "CD/ROM not found".
hshib over 9 years

You can copy everything with single command with - "cp -r /tmp/bootiso/. /tmp/bootisoks/" (this is a little tricky - note single . after /tmp/bootiso/)
Aaron Copley over 9 years

Sorry, about that. I probably missed those periods in my notes that I copied this answer from? My media was definitely created successfully so I am sure I had .treeinfo and .discinfo in the final ISO. Apologies for the additional troubleshooting you had to do. I'll update the answer.
user1603454 over 8 years

@Aaron Copley Thank you for your instructure. I followed it. but, the iso file which is made by the last command is not as the same size of original iso. The original one is (1.1G) but the new iso is 34MG. and it is not working?
Aaron Copley over 8 years

@user1603454 You probably don't want to create an ISO for just the contents of ./isolinux. Modify step 9 as necessary..
Shane almost 7 years

Apologies for bumping the old thread... I was having issues with the built ISO hanging at 'Starting dracut initqueue hook.' - and the solution was to add a -V flag to the mkisofs flag.
gcharbon almost 6 years

I followed the steps as mentioned here. Everything worked fine as long as I skipped step 8. If I add rpms to Packages directory and then run createrepo -dpo .. . I encounter an error during install: noSuchGroup: core. Do I need to create another repo and let the existing repo intact or did anyone manage to modify the existing repo without problem ? I don't know if I should open a new question.
Aaron Copley almost 6 years

@gcharbon You'll need to modify the createrepo command to include the groups file. That way your repository contains group metadata. If you sort it out, please feel free to update the answer above.
peachykeen almost 5 years

@gcharbon were you able to figure out how to modify createrepo to include the groups file? I am struggling trying to add my own RPMs to the kickstart file.
gcharbon almost 5 years

@peachykeen I stopped struggling with Kickstart files, instead I use Centos Cloud images and cloud-init. It proved to be much simpler (I also use Ansible to automate the download of images, the generation of cloud init files from templates, then the generation of cloud-init ISO seeds)