lib/zfs.js
function unmount(opts, cb) {
    "use strict";
    
    var params = [ 'unmount' ];
    
    if (opts.force) {
        params.push('-f');
    }
    
    if (opts.name) {
        params.push(opts.name);  
    } else {
        params.push('-a');
    }
    
    zfs(params, cb);
}
function unmount(opts, cb) {
    "use strict";
    
    var params = [ 'unmount' ];
    
    if (opts.force) {
        params.push('-f');
    }
    
    if (opts.name) {
        params.push(opts.name);  
    } else {
        params.push('-a');
    }
    
    zfs(params, cb);
}
/*

Unmount the specified filesystem|mountpoint

PARAMS:
opts: {
name: string // the name of the zfs dataset or the path of the mountpoint.
if the dataset is null, then unmount all available filesystems with '-a'
force: boolean // whether forcely unmount even if the filesystem is still in use.
}