Hello,
From inside a CT:
nice -n -10 ls
nice: cannot set niceness: Permission denied
Is there any way to be able to set a high (< 0) nice priority to a process from inside the CT ?
Not inside an unprivileged container, no, otherwise it’d allow for containers to effectively DoS the host and all other containers.
It’s a kernel protection measure put in place for all unprivileged users.