NFSv4 on Virtual Box VMs

Setting up NFSv4 mounts from the host (server) to the VirtualBox VM (client): You can't use the normal NAT network - you'll get "Operation not permitted". Setup a host-only network, and configure those devices on the host and vms. That allows the connection to proceed to the next point.

Locations in Ubuntu datetime indicator

Ubuntu datetime indicator is a right pain to add extra timezones to.
The Locations... seems to be very poor when you try to add a new location at determining locations' full entry.
As an alternative you can add them to the configuration directly.

• First install dconf-editor.
• Open dconf-editor.
• Navigate to con/canonical/indicator/datetime and edit the locations item with the locations you want.

Valid locations:

• UTC UTC
• America/Vancouver Vancouver
• Australia/Sydney Sydney
• Pacific/Auckland Auckland
• Asia/Tokyo Tokyo
• America/Toronto Ottawa

Programmatically find out if a file is sparse

You can work out if a file is sparse using stat (or fstat etc).

    struct stat statbuf;
    int ret = ::stat(tmp, &tatbuf);
    ASSERT_NE(ret, -1);

    // statbuf.st_size - virtual size in bytes
    // statbuf.st_blocks - physical size in 512-byte blocks

So if st_blocks * 512 < st.size then you definitely have a sparse file.