# Problems attaching reference sequence with add\_sequence() on UKB RAP

**URL:** <https://discuss.hail.is/t/problems-attaching-reference-sequence-with-add-sequence-on-ukb-rap/4243>\
**Category:** Hail Query & hailctl\
**Created:** [March 3, 2026, 6:33pm UTC](https://discuss.hail.is/t/problems-attaching-reference-sequence-with-add-sequence-on-ukb-rap/4243 "2026-03-03T18:33:43Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![jbs](https://avatars.discourse-cdn.com/v4/letter/j/5fc32e/32.png) [@jbs](https://discuss.hail.is/u/jbs)\
**Post date:** [March 6, 2026, 6:13pm UTC](https://discuss.hail.is/t/problems-attaching-reference-sequence-with-add-sequence-on-ukb-rap/4243/2 "2026-03-06T18:13:24Z")

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Follow up: initializing Hail pointing to the database file system as described [here](https://discuss.hail.is/t/how-should-i-use-hail-on-the-dnanexus-rap/2277?utm_source=chatgpt.com) doesn’t resolve this either, throwing the same error irrespective of where the fasta and fasta.fai files are stored. The initialization step looks like:

```python
import pyspark
import dxpy
import hail as hl

db_name = "db"
db_uri = dxpy.find_one_data_object(
    name = db_name, 
    classname = "database"
)['id']

sc = pyspark.SparkContext()
spark = pyspark.sql.SparkSession(sc)

hl.init(sc = sc, tmp_dir = f'dnax://{db_uri}/tmp/')

```

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