cmdline.txt Builder

cmdline.txt is a single line of kernel parameters consumed by the bootloader. Toggle the options you want; the right column shows the full one-line file.

Critical: the file must contain exactly one line — no line wrapping. The bootloader silently ignores anything after the first newline. Always paste with echo "..." | sudo tee /boot/firmware/cmdline.txt, not a wrap-friendly editor.

Where this file lives: /boot/firmware/cmdline.txt on Bookworm and later, /boot/cmdline.txt on Bullseye and earlier.

Don't edit if you're not sure: a malformed cmdline can leave the Pi unable to boot. The fix: SD card into another machine, restore the line. Stock cmdline for reference: console=serial0,115200 console=tty1 root=PARTUUID=xxxxxxxx-02 rootfstype=ext4 fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles

PARTUUID: the safest way to identify the root partition — it survives reflashing, unlike /dev/mmcblk0p2. Read yours with cat /etc/fstab or blkid.

cgroups for Docker: Bookworm uses cgroup v2 by default (managed by systemd); the controllers are compiled into the Pi kernel. The toggles in the cgroups section above are cgroup v1 flags — only relevant on older OS releases or when forcing v1 with systemd.unified_cgroup_hierarchy=0.