dlopen cannot load shared library

[Mark Shuttleworth]

On 03/02/17 12:41, Loïc Minier wrote:
> In classic mode, you see libraries from your classic Ubuntu system
> including X11; in devmode/confined mode, you only see system libraries
> from the core snap which doesn't contain X11.

One more point. If you try this command you will be running a shell
"inside the snap", in other words, you will be experiencing the
filesystem exactly as your snap sees it.

  $ snap run --shell <snap>

Now you are living inside the container that is setup just for that
snap. It's using the same sorts of mechanisms as LXD and Docker to keep
processes apart, but it is also setup in such a way that files can be
shared across snaps. You can see the environment variables that snapd
has setup so snap processes can find out where they can write data etc:

  $ set | grep SNAP
  SNAP=/snap/etcd/x5
  SNAP_ARCH=amd64
  SNAP_COMMON=/var/snap/etcd/common
  SNAP_DATA=/var/snap/etcd/x5
  SNAP_LIBRARY_PATH=/var/lib/snapd/lib/gl:
  SNAP_NAME=etcd
  SNAP_REEXEC=
  SNAP_REVISION=x5
  SNAP_USER_COMMON=/home/mark/snap/etcd/common
  SNAP_USER_DATA=/home/mark/snap/etcd/x5
  SNAP_VERSION=2.3.7

And if you start using 'ls' to poke around the filesystem, you quickly
see that you are in your own special world:

  $ ls /
  ls: cannot open directory '/': Permission denied

  $ sudo ls /
  bash: /usr/bin/sudo: Permission denied

  $ ls -l /lib/
  total 74
  drwxr-xr-x  2 root root    52 Jan 13 20:41 apparmor
  drwxr-xr-x  2 root root    57 Jan 13 20:41 bridge-utils
  drwxr-xr-x  2 root root    40 Jan 13 20:41 cgmanager
  drwxr-xr-x  3 root root    89 Jan 13 20:41 crda
  drwxr-xr-x  2 root root     3 Jan 13 20:40 firmware
  drwxr-xr-x  2 root root  1032 Jan 13 20:41 i386-linux-gnu
  drwxr-xr-x  2 root root    59 Jan 13 20:41 ifupdown
  drwxr-xr-x  2 root root    51 Jan 13 20:41 init
  -rwxr-xr-x  1 root root 70952 Sep 22 18:34
klibc-k3La8MUnuzHQ0_kG8hokcGAC0PA.so
  lrwxrwxrwx  1 root root    25 Nov 16 22:51 ld-linux.so.2 ->
i386-linux-gnu/ld-2.23.so
  drwxr-xr-x  3 root root    61 Jan 13 20:41 lsb
  drwxr-xr-x  2 root root    35 Jan 13 20:41 modprobe.d
  drwxr-xr-x  6 root root  4096 Jan 26 10:15 modules
  drwxr-xr-x  2 root root    31 Jan 13 20:41 netplan
  drwxr-xr-x  2 root root    35 Jan 13 20:41 resolvconf
  drwxr-xr-x  8 root root  1057 Jan 13 20:41 systemd
  drwxr-xr-x 15 root root   132 Jan 13 20:41 terminfo
  drwxr-xr-x  4 root root   298 Jan 13 20:41 udev
  drwxr-xr-x  3 root root  4281 Jan 13 20:41 x86_64-linux-gnu
  drwxr-xr-x  2 root root  2531 Jan 13 20:41 xtables

So you see, this is a super-minimal "core" with just a few libraries.

You can find your snap at $SNAP:

  $ echo $SNAP
  /snap/foo/7
  $ ls -lR $SNAP
  /snap/foo/x5:
  ... <your snap tree here>

Hope that's a useful introduction. It's a lot of fun once you realise
that you have TOTAL control over your snap, but everything else is very
structured for you.

Mark
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.ubuntu.com/archives/snapcraft/attachments/20170203/11b9a99f/attachment.html>