IO Scheduler Setup

Small interactive helper to inspect and set block device I/O schedulers, and persist a chosen scheduler across reboots using a udev rule.

---

Table of Contents

• Status
• Features
• Requirements
• Usage
• Examples
• Design Notes
• Limitations & Next Steps
• Contributing
• License

Status

• Basic interactive script saved at io-scheduler-setup.sh. Intended for manual use on systems where /sys/block/<dev>/queue/scheduler is writable.

Features

• Enumerates block disks with lsblk and shows model/size/rotational flag.
• Reads available schedulers from /sys/block/<dev>/queue/scheduler.
• Applies a scheduler immediately (writes to sysfs).
• Optionally writes a udev rule at /etc/udev/rules.d/99-io-scheduler.rules to make the scheduler selection persistent across reboots. The 99- prefix ensures this rule runs after all system defaults (e.g. 60-ioschedulers.rules from systemd-udev which resets NVMe to none).
• Provides --remove <dev> to remove rules created for a device.

Requirements

• A Linux kernel and distribution that expose /sys/block/<dev>/queue/scheduler.
• bash, lsblk, udevadm, and basic shell utilities (awk, sed, grep).
• Root privileges to write sysfs and to create udev rules (script will escalate via sudo).

Usage

1. Make the script executable from the IO Scheduler Setup directory:

chmod +x io-scheduler-setup.sh

2. Run interactively (recommended):

sudo ./io-scheduler-setup.sh

3. Remove previously created udev rules for a device:

sudo ./io-scheduler-setup.sh --remove sda

Note

• Persistent udev rules are written to /etc/udev/rules.d/99-io-scheduler.rules.
• The 99- prefix guarantees this file is processed after system defaults that would otherwise override your choice.
• The script backs up an existing rule file before appending new entries.

Examples

• Inspect disks and set scheduler interactively:

sudo ./io-scheduler-setup.sh
# follow prompts to choose disk, apply scheduler, and optionally persist it

• Create a persistent rule for /dev/sdb (example interactive flow):
  • Choose /dev/sdb in the menu
  • Apply desired scheduler (optional)
  • Choose to create persistent udev rule and enter the desired scheduler

Design Notes

• The script prefers to match devices by their kernel name (e.g. sda) when writing udev rules: SUBSYSTEM=="block", KERNEL=="sda", ATTR{queue/scheduler}=="<sched>".
• This keeps rules simple and predictable; for more advanced per-model rules you can edit the generated /etc/udev/rules.d/60-io-scheduler.rules manually.
• After writing rules the script reloads udev rules and triggers a change event for the affected device.

Limitations & Next Steps

• Not all block devices allow changing the scheduler at runtime (some device/driver stacks ignore writes to /sys/block/.../queue/scheduler). If writing fails, the script reports the error.
• NVMe vs SATA: device naming differs (nvme0n1 vs sda) — the script lists all block disks so pick the exact kernel name printed by the menu.
• Future improvements: add a dry-run mode, allow matching by WWN or model for more permanent device identification, and add unit tests or a validation mode that runs on non-root to show proposed changes.

Contributing

• Bug reports and improvements welcome. Keep changes small and avoid running untrusted code as root. When modifying udev behavior, prefer clear, documented rules and make backups of /etc/udev/rules.d/60-io-scheduler.rules.

License

• MIT