Overriding Nextflow Parameters with Commandline Arguments - nextflow

Question

Given the following nextflow.config:
google {
project = "cool-project"
region = "europe-west4"
lifeSciences {
bootDiskSize = "200 GB"
debug = true
preemptible = true
}
}
Is it possible to override one or more of those settings using command line arguments. For example, if I wanted to specify that no preemptible machines should be used, can I do the following:
nextflow run main.nf -c nextflow.config --google.lifeSciences.preemptible false
?

Answer 1

Overriding pipeline parameters can be done using Nextflow's command line interface by prefixing the parameter name with a double dash. For example, put the following in a file called 'test.nf':
#!/usr/bin/env nextflow
params.greeting = 'Hello'
names = Channel.of( "foo", "bar", "baz" )
process greet {
input:
val name from names
output:
stdout result
"""
echo "${params.greeting} ${name}"
"""
}
result.view { it.trim() }
And run it using:
nextflow run -ansi-log false test.nf --greeting 'Bonjour'
Results:
N E X T F L O W ~ version 20.10.0
Launching `test.nf` [backstabbing_cajal] - revision: 431ef92cef
[46/22b4f0] Submitted process > greet (1)
[ca/32992c] Submitted process > greet (3)
[6e/5880b0] Submitted process > greet (2)
Bonjour bar
Bonjour foo
Bonjour baz
This works fine for pipeline params, but AFAIK there's no way to directly override executor config like you describe on the command line. You can however, just parameterize these values and set them on the command line like described above. For example, in your nextflow.config:
params {
gc_region = false
gc_preemptible = true
...
}
profiles {
'test' {
includeConfig 'conf/test.config'
}
'google' {
includeConfig 'conf/google.config'
}
...
}
And in a file called 'conf/google.config':
google {
project = "cool-project"
region = params.gc_region
lifeSciences {
bootDiskSize = "200 GB"
debug = true
preemptible = params.gc_preemptible
}
}
Then you should be able to override these in the usual way:
nextflow run main.nf -profile google --gc_region "europe-west4" --gc_preemptible false
Note that you can also specify multiple configuration profiles by separating the profile names with a comma:
nextflow run main.nf -profile google,test ...