Building an unattended RHEL install with a Kickstart file

Goal

Write a Kickstart file that installs RHEL (or a rebuild) with no interactive prompts, catch syntax errors before booting anything, and avoid leaking credentials through the file itself.

Prerequisites

A way to serve the file to the installer (HTTP(S), or embedded on install media) and a boot method that can pass a kernel argument (PXE, an ISO's boot menu, or a virt-install argument).

Steps

1. Structure the file as one-line commands (lang, keyboard, timezone, network, partitioning, rootpw) plus a %packages section listing groups and package names, closed with %end. Add scriptlet sections where logic is needed: %pre runs before installation (for example, to compute a partition layout from detected disks), %post runs after the base install, inside the new system's own root, for configuration.
2. Validate the file before using it anywhere, without booting anything:

ksvalidator /path/to/ks.cfg

ksvalidator flags unknown or deprecated commands, but it cannot check that a referenced repository or package actually exists. 3. Serve it and pass it at boot. inst.ks= is Anaconda's own boot option for pointing at a kickstart source:

inst.ks=http://server/ks.cfg

appended to the kernel command line in PXE/grub, or passed as extra boot arguments to virt-install. 4. Keep secrets out of the file. A kickstart served over plain HTTP for PXE is typically unauthenticated, and copies stay on the finished host (/root/anaconda-ks.cfg, and on current releases also the unmodified /root/original-ks.cfg) — never place a live root password, activation key or join token directly in rootpw or a %post line. Use rootpw --lock (SSH key access only) and fetch any real secret inside %post from a runtime source instead of embedding it. 5. Test the whole file in a disposable VM before pointing it at real hardware.

Expected result

The installer runs start to finish with no prompts; ksvalidator exits 0; neither /root/anaconda-ks.cfg nor /root/original-ks.cfg on the finished host contains a live credential.

Limits and test basis

ksvalidator checks kickstart syntax, not your %post script's correctness or the target's package availability — a VM dry run is the only real test. Kickstart commands are occasionally deprecated between releases; re-run ksvalidator against a file written for an older release before reusing it on a newer one.