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[DRAFT] How to create custom CentOS like Linux distro iso

Tags: #CentOS #Linux #anaconda #custom distro #hacking #lorax

QuickStart

There are three possible types of iso: * Regular bootable iso (just like CentOS-7.3-Everything) - I will tell here about this one * Live-iso (just like Fedora-Workstation-Rawhide) - I would try to do it and tell you in futher posts * Both bootable & live (just like Ubuntu :-S) - It is my goal. I do not know how to create it now, but I would like to do it

Here is just QuickStart for creating custom bootable iso. Feel free to send PR, issues and proposes if you don't understand something.

  • Run lorax to get minimal boot.iso. Remember all used arguments, like -p, --volid!
  • mount boot.iso and copy all its content
setenforce 0
lorax ... "$LORAX_TMP_DIR"
...
buildroot=/build/lorax
mount -o loop,ro "$LORAX_TMP_DIR/images/boot.iso" "$TMP_MOUNT_DIR"
rm -rf "$buildroot"
cp -apr "$TMP_MOUNT_DIR" "$buildroot"
cp -a $LORAX_TMP_DIR/.discinfo "$buildroot"
cp -a $LORAX_TMP_DIR/.treeinfo "$buildroot"
...
# Add all needed rpms into `$buildroot/Packages/` manually
pushd $buildroot
mkdir -p Packages
cp ...mypackages/*.rpm Packages/

# create repo
mkdir repodata
cp ../my-centos-comps.xml repodata/comps-$DISTRO_NAME.xml
createrepo -d -g "repodata/comps-$DISTRO_NAME.xml" .
  • fix isolinux/isolinux.cfg - regular bootloader config
  • fix EFI/BOOT/grub.cfg - efi bootloader config
  • create product.img with needed info
    • custom_kickstart (ks for interactive installation with some desired defaults)
    • custom installclasses/custom.py, with distroname and some fixes
  • add GPG-keys for custom packages (or put them inside centos-release.rpm (prefered). Do not forget to put them into installed OS then
  • add kickstart if you want (and use it in grub.cfg, isolinux.cfg)
  • creating iso. You can take a look into lorax's x86.tmpl. In my script it looks like: #!/bin/bash genisoimage -U -J -R -T -joliet-long \ -b isolinux/isolinux.bin \ -c isolinux/boot.cat \ -boot-load-size 4 -boot-info-table -no-emul-boot \ -eltorito-alt-boot \ -e images/efiboot.img -no-emul-boot \ -input-charset utf8 \ -V "$DISTRO_NAME" \ -sysid "X86_64" \ -publisher "my complany" \ -o "$filepath" "$buildroot"
    • IMORTANT: isolinux/boot.cat - it is why we need to unpack boot.iso, and use it, instead of taking raw lorax-output-root (which contains images/boot.iso, which not needed).
    • IMORTANT: -V VOLID must be same as we use in lorax --volid and as we use in isolinux.cfg for booting
  • isohybrid --uefi "$filepath" --- need to make USB bootable after dd if=myiso.iso of=/dev/sdb
  • implantisomd5 --supported-iso "$filepath"