can't npm install

[andrelec1]

i try to use you lib but i can't install :/
i have Onion Omega2+ with a 2go sdcard ...

~/.npmrc :

    prefix="/tmp/mounts/SD-P1/.npm-global"
    cache="/tmp/mounts/SD-P1/.npm-cache"

i try to install module and i get :

root@Omega-B321:/tmp/run/mountd/mmcblk0p1/project# npm install github:sdesalas/node-serialport-omega2
npm ERR! Linux 4.4.46
npm ERR! argv "/usr/bin/node" "/usr/bin/npm" "install" "github:sdesalas/node-serialport-omega2"
npm ERR! node v4.3.1
npm ERR! npm  v2.14.12
npm ERR! path /tmp/mounts/SD-P1/.npm-cache/_git-remotes/_templates
npm ERR! code EPERM
npm ERR! errno -1
npm ERR! syscall chown

npm ERR! Error: EPERM: operation not permitted, chown '/tmp/mounts/SD-P1/.npm-cache/_git-remotes/_templates'
npm ERR!     at Error (native)
npm ERR!  { [Error: EPERM: operation not permitted, chown '/tmp/mounts/SD-P1/.npm-cache/_git-remotes/_templates']
npm ERR!   errno: -1,
npm ERR!   code: 'EPERM',
npm ERR!   syscall: 'chown',
npm ERR!   path: '/tmp/mounts/SD-P1/.npm-cache/_git-remotes/_templates' }
npm ERR!
npm ERR! Please try running this command again as root/Administrator.

npm ERR! Please include the following file with any support request:
npm ERR!     /tmp/run/mountd/mmcblk0p1/project/npm-debug.log