$ sudo -H vserver blah enter
Password:
vnamespace: vc_xidopt2xid("/etc/vservers/blah"): No such file or directory

(no, blah is not the real name) ... but the directory is there:

$ ls -la /etc/vservers/blah
total 9
drwxr-xr-x  6 root root 272 2007-02-26 23:22 .
drwxr-xr-x 19 root root 576 2007-06-18 22:13 ..
drwxr-xr-x  4 root root  96 2007-02-16 23:09 apps
lrwxrwxrwx  1 root root  45 2007-02-16 23:09 cache -> /etc/vservers/.defaults/cachebase/blah
drwxr-xr-x  2 root root  48 2007-02-16 23:09 cpuset
-rw-r--r--  1 root root  72 2007-02-26 23:22 fstab
drwxr-xr-x  3 root root  72 2007-02-16 23:09 interfaces
-rw-r--r--  1 root root  12 2007-02-16 23:09 name
lrwxrwxrwx  1 root root  29 2007-02-16 23:09 run -> /var/run/vservers/blah
drwxr-xr-x  2 root root  72 2007-02-16 23:09 uts
lrwxrwxrwx  1 root root  44 2007-02-16 23:09 vdir -> /etc/vservers/.defaults/vdirbase/blah