trying to add disk to asm

I set the environment to asm
Log in with sysasm
And run

alter diskgroup cert_dg1
add disk '/dev/oracleasm/cert_asmdisk118'

but get:

ERROR at line 1:
ORA-15032: not all alterations performed ORA-15031: disk specification '/dev/oracleasm/cert_asmdisk118' matches no disks

What am I doing wrong?

Brian

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