[lxc-users] PATH set weirdly in an unprivileged container ?

[Stéphane Graber]

On Fri, Mar 03, 2017 at 05:27:25PM +0100, Benoit Barthelet wrote:
> Hello,
> 
> It's my first few hours playing with containers so maybe there's something
> I'm doing wrong or something I overlook, or both.
> 
> I'm on debian stretch if that's relevant, using :
> 
> ➜  ~ lxc-info --version
> 2.0.7
> 
> I set up an unprivileged container this way:
> 
> ➜  ~ lxc-create -t download -n u1 -- -d ubuntu -r xenial -a amd64
> Using image from local cache
> Unpacking the rootfs
> 
> ---
> You just created an Ubuntu container (release=xenial, arch=amd64,
> variant=default)
> 
> To enable sshd, run: apt-get install openssh-server
> 
> For security reason, container images ship without user accounts
> and without a root password.
> 
> Use lxc-attach or chroot directly into the rootfs to set a root password
> or create user accounts.
> 
> I then start it and attach:
> 
> ➜  ~ lxc-start -n u1
> ➜  ~ lxc-attach -n u1
> root at u1:/# echo $PATH
> /home/HOST_USER/bin:/usr/local/bin:/home/HOST_USER/Applications/.bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games

lxc-attach uses its own environment inside the container. There are a
number of lxc-attach options to alter this behavior.

> 
> Now as you can see /sbin is not in the PATH, which means any apt-get
> install BLABLABLA ends up with the following error:
> 
> dpkg: warning: 'ldconfig' not found in PATH or not executable
> dpkg: warning: 'start-stop-daemon' not found in PATH or not executable
> dpkg: error: 2 expected programs not found in PATH or not executable
> Note: root's PATH should usually contain /usr/local/sbin, /usr/sbin and
> /sbin
> E: Sub-process /usr/bin/dpkg returned an error code (2)
> 
> If I do the exact same commands with sudo, thus creating a NOT unprivileged
> container, if I got it correctly, well the PATH is "correctly" set up, at
> least /sbin is in it and I can apt-get install anything.
> 
> When I say correctly I should say: the way I would expect it when I'm root.
> That makes me think there's a subtlety about unprivileged container I don't
> get.
> 
> Asking in IRC, I got this answer, which works, I should use:
> 
> ➜  ~ lxc-execute -n u1 -- /bin/bash --login
> 
> 
> Now reading both man pages for attach and execute, at first glance they
> seem to be doing the same except one spawn the instance while the other
> doesn't and uses the one that is running.
> 
> Again it's been only a few hours I'm playing with it.
> 
> I don't get why in the case of the container created with sudo the PATH is
> "correct", and not in the case of the unprivileged container.
> 
> Is it intended ? It's kind of weird to be root in a machine and unable to
> install a package because of the PATH, hence those questions.
> 
> Looking at the templates, it seems they export that PATH
> 
> ➜  ~ grep PATH /usr/share/lxc/templates/lxc-ubuntu
> # Make sure the usual locations are in PATH
> export PATH=$PATH:/usr/sbin:/usr/bin:/sbin:/bin
> 
> So the -t download switch doesn't use that ?
> 
> 
> Thanks in advance
> 
> 
> -- 
> benoit barthelet
> http://pgp.mit.edu/pks/lookup?op=get&search=0xF150E01A72F6D2EE

> _______________________________________________
> lxc-users mailing list
> lxc-users at lists.linuxcontainers.org
> http://lists.linuxcontainers.org/listinfo/lxc-users


-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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