# Optional Configuration for rose-suite.conf
**URL:** https://cms-helpdesk.ncas.ac.uk/t/optional-configuration-for-rose-suite-conf/1756
**Category:** Rose/Cylc and FCM
**Tags:** ARCHER2
**Created:** [23 July 2025 15:48 UTC](https://cms-helpdesk.ncas.ac.uk/t/optional-configuration-for-rose-suite-conf/1756 "2025-07-23T15:48:54Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@ajw1g19](https://cms-helpdesk.ncas.ac.uk/u/ajw1g19)
#### Post date: [23 July 2025 15:48 UTC](https://cms-helpdesk.ncas.ac.uk/t/optional-configuration-for-rose-suite-conf/1756/1 "2025-07-23T15:48:54Z")
Dear CMS Helpdesk,
Could you explain how to create an optional configuration file that can override variables in the rose-suite.conf file? I understand the process for different rose-app.conf files but documentation is unclear on how this works for rose-suite.conf.
I’m using cylc 7.8.12 for reference.
Thank you,
Alfred
---
### Author:  [@grenville](https://cms-helpdesk.ncas.ac.uk/u/grenville)
#### Post date: [23 July 2025 16:40 UTC](https://cms-helpdesk.ncas.ac.uk/t/optional-configuration-for-rose-suite-conf/1756/2 "2025-07-23T16:40:44Z")
Create a directory called `opt` at the top level of the suite. In `opt`, create a file with the overrides - here’s an example - it needs the prefix `rose-suite-`
`rose-suite-n1280o12_PI1850_7p5m.conf`
that contains in this case:
```auto
[grenvill@puma2 opt]$ cat rose-suite-n1280o12_PI1850_7p5m.conf
[jinja2:suite.rc]
ATM_PROCX=114
ATM_PROCY=60
ATMOS_TIMESTEPS_PER_DAY=360
ANCIL_OPT_KEYS='n1280o12'
XIOS_NPROC=144
```
Then in rose-suite.conf, add the opts line
```auto
[grenvill@puma2 u-dr523]$ cat rose-suite.conf
opts=n1280o12_PI1850_7p5m
```
Grenville
---
### Author:  [@ajw1g19](https://cms-helpdesk.ncas.ac.uk/u/ajw1g19)
#### Post date: [23 July 2025 17:33 UTC](https://cms-helpdesk.ncas.ac.uk/t/optional-configuration-for-rose-suite-conf/1756/3 "2025-07-23T17:33:54Z")
Thank you Grenville!