tentativo chroot

[root@arch saul]# mount /dev/sdb2 /mnt/gentoo
[root@arch saul]# mount --rbind /dev /mnt/gentoo/dev
[root@arch saul]# mount --make-slave /mnt/gentoo/dev
[root@arch saul]# mount -t proc /proc /mnt/gentoo/proc
[root@arch saul]# mount --rbind /sys /mnt/gentoo/sys
[root@arch saul]# mount --make-slave /mnt/gentoo/sys
[root@arch saul]# mount --rbind /tmp /mnt/gentoo/tmp
[root@arch saul]# chroot /mnt/gentoo
arch / # env-update
bash: env-update: command not found
[root@arch saul]# chroot /mnt/gentoo /bin/bash
arch / # env-update
bash: env-update: command not found

[root@arch saul]# chroot /mnt/gentoo /usr/bin/bash
chroot: failed to run command ‘/usr/bin/bash’: File o directory non esistente
[root@arch saul]# chroot /mnt/gentoo /usr/bin/
chroot: failed to run command ‘/usr/bin/’: Permesso negato