526f1c1afd
- Complete documentation for all bootc commands and subcommands - Debian-specific adaptations and workarounds - Manual installation methods to bypass bootc reliability issues - Technical guides with Rust source code analysis - Flowcharts and external command references - Hidden command documentation (bootc internals, state, etc.) - Composefs integration analysis - Base image creation guides (with and without bootc binary) - Management scripts and automation - Comprehensive troubleshooting and examples
101 lines
3.4 KiB
Markdown
101 lines
3.4 KiB
Markdown
# Kernel arguments
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The default bootc model uses "type 1" bootloader config files stored in `/boot/loader/entries`, which define arguments provided to the Linux kernel.
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The set of kernel arguments can be machine-specific state, but can also be managed via container updates.
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The bootloader entries are currently written by the OSTree backend.
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More on Linux kernel arguments: [Kernel Parameters](https://docs.kernel.org/admin-guide/kernel-parameters.html)
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## /usr/lib/bootc/kargs.d
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Many bootc use cases will use generic "OS/distribution" kernels. In order to support injecting kernel arguments, bootc supports a small custom config file format in `/usr/lib/bootc/kargs.d` in TOML format, that have the following structure:
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```toml
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[kargs]
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append = ["console=ttyS0", "quiet"]
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prepend = ["rd.luks.uuid=12345678-1234-1234-1234-123456789abc"]
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```
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The `append` and `prepend` arrays contain kernel arguments that will be added to the kernel command line. Arguments in `prepend` are added at the beginning, while `append` arguments are added at the end.
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## Local kernel argument management
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It is currently undefined behavior to remove kernel arguments locally that are included in the base image via `/usr/lib/bootc/kargs.d`.
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## Injecting default arguments into custom kernels
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The Linux kernel supports building in arguments into the kernel binary, at the time of this writing via the `config CMDLINE` build option. If you are building a custom kernel, then it often makes sense to use this instead of `/usr/lib/bootc/kargs.d` for example.
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## Debian-Specific Considerations
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### Debian Kernel Management
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When working with Debian bootc images:
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- **Kernel packages**: Debian provides multiple kernel packages (linux-image-generic, linux-image-cloud, etc.)
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- **Kernel headers**: Install `linux-headers-*` packages for development
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- **Kernel modules**: Located in `/lib/modules/$(uname -r)/`
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### Example Debian Kernel Configuration
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```dockerfile
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FROM debian:bookworm-slim
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# Install kernel and bootc dependencies
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RUN apt update && \
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apt install -y linux-image-generic linux-headers-generic bootc ostree && \
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apt clean && \
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rm -rf /var/lib/apt/lists/*
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# Configure kernel arguments for Debian
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COPY kargs.d/99-debian.conf /usr/lib/bootc/kargs.d/
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```
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### Debian Bootloader Integration
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Debian uses GRUB as the default bootloader:
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- **GRUB configuration**: `/etc/default/grub`
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- **GRUB scripts**: `/etc/grub.d/`
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- **Update GRUB**: `update-grub` command
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### Example kernel arguments configuration
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Create `/usr/lib/bootc/kargs.d/99-debian.conf`:
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```toml
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[kargs]
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append = [
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"console=ttyS0",
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"quiet",
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"splash",
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"systemd.show_status=false"
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]
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prepend = [
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"rd.luks.uuid=12345678-1234-1234-1234-123456789abc"
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]
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```
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### Debian Security Considerations
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For Debian bootc images, consider these security-related kernel arguments:
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- **AppArmor**: `apparmor=1 security=apparmor`
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- **SELinux**: `selinux=1 security=selinux` (if using SELinux)
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- **KASLR**: `kaslr` (Kernel Address Space Layout Randomization)
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- **SMEP/SMAP**: `nosmep nosmap` (if needed for compatibility)
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### Hardware-Specific Arguments
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Debian bootc images may need hardware-specific kernel arguments:
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- **Virtualization**: `console=ttyS0` for cloud instances
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- **Storage**: `root=UUID=...` for specific root device
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- **Network**: `net.ifnames=0` for predictable network interface names
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---
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The Linux Foundation® (TLF) has registered trademarks and uses trademarks. For a list of TLF trademarks, see Trademark Usage.
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