Before:
```shell
% chflags uunlink foo
chflags: foo: Operation not supported
% chflags sunlink foo
chflags: foo: Operation not permitted
% sudo chflags sunlink foo
% uname -a
FreeBSD gilot.local 14.1-RELEASE-p4 FreeBSD 14.1-RELEASE-p4 GENERIC amd64
```
After:
```shell
fbsd-current# mdconfig -a -t malloc -s 100m
md0
fbsd-current# mdconfig -a -t malloc -s 100m
md1
fbsd-current# zpool create howitzer md0 md1
fbsd-current# cd /howitzer
fbsd-current# : > foo
fbsd-current# chflags uunlink foo
fbsd-current# ls -l
total 1
-rw-r--r-- 1 root wheel 0 Nov 29 10:44 foo
fbsd-current# rm foo
rm: foo: Operation not permitted
fbsd-current# chflags nouunlink foo
fbsd-current# rm foo
fbsd-current#
```