[Pkg-ltsp-devel] Bug#875821: ltsp-client-core: /rofs is mounted on NFS - we get Operation not supported when using sudo -iu <username> as root

[Rainer Stumbaum]

Package: ltsp-client-core
Version: 5.5.9-2
Severity: important
Tags: upstream

Dear Maintainer,

we are upgrading our LTSP image from jessie to stretch.  We are running
LTSP against HA NFS servers since 2010 (previously SUN storage systems
(ZFS based), since 2013 against NetApp filers). We encountered
the following problem:
- LTSP stretch client starts up fine
- SSH daemon on the LTSP client is enabled and starts up fine
- Connecting via SSH does not work
- Login in as root on the LTSP client console works fine
- sudo -iu <username> gives the following error
"sudo: unable to execute /bin/bash: Operation not supported"
- Using strace we found that seresuid and then accessing a file gives a
  problem  with the filesystem (overlay on top of NFS)
- We wrote a small C program  to replicate the error and found that
  overlay on top of NFS gives the above "Operation not supported"
  whereas NFS directly works fine (/bin/bash (overlay) vs.
  /rofs/bin/bash (NFS)).

After touching /bin/bash and therefore copying to upper fs /bin/bash
works fine for some UIDs but not for all user IDs.

Best regards
Rainer

-- System Information:
Debian Release: 9.1
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-3-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages ltsp-client-core depends on:
ii  console-setup    1.164
ii  init             1.48
ii  initramfs-tools  0.130
ii  iproute          1:4.9.0-1
ii  iproute2         4.9.0-1
ii  kbd              2.0.3-2+b1
ii  libc6            2.24-11+deb9u1
ii  libpopt0         1.16-10+b2
ii  lsb-base         9.20161125
ii  lsb-release      9.20161125
ii  nbd-client       1:3.15.2-3
ii  pxelinux         3:6.03+dfsg-14.1
ii  python           2.7.13-2
ii  syslinux-common  3:6.03+dfsg-14.1
ii  tftp-hpa         5.2+20150808-1+b1

Versions of packages ltsp-client-core recommends:
ii  acpi-support-base  0.142-8
ii  dbus               1.10.18-1
ii  dnsutils           1:9.10.3.dfsg.P4-12.3+deb9u2
ii  pciutils           1:3.5.2-1
ii  procps             2:3.3.12-3

Versions of packages ltsp-client-core suggests:
pn  alsa-utils                        <none>
ii  cron                              3.0pl1-128+b1
pn  cryptsetup                        <none>
pn  cups-bsd                          <none>
pn  freerdp-x11 | rdesktop            <none>
pn  inputattach | joystick            <none>
pn  ldm                               <none>
pn  libasound2-plugins                <none>
pn  ltspfsd                           <none>
ii  netcat-openbsd [netcat]           1.130-3
ii  netcat-traditional [netcat]       1.10-41+b1
ii  ntpdate                           1:4.2.8p10+dfsg-3
pn  numlockx                          <none>
pn  pulseaudio                        <none>
pn  python-serial                     <none>
ii  rsyslog [system-log-daemon]       8.24.0-1
ii  sane-utils                        1.0.25-4.1
pn  sdm-terminal | x-display-manager  <none>
pn  sshfs                             <none>
ii  x11-xserver-utils                 7.7+7+b1

-- Configuration Files:
/etc/ltsp/update-kernels.conf changed:
BOOT_METHODS="NFS"
CMDLINE_LINUX_DEFAULT="init=/sbin/init-ltsp quiet"
CMDLINE_NFS="root=/dev/nfs ip=dhcp boot=nfs NFSOPTS=\"-o timeo=100,retrans=360,hard,nointr,nocto,noacl,acregmin=600,acregmax=600,acdirmin=600,acdirmax=600\" vmwgfx.enable_fbdev=1 vga=0x317 cgroup_enable=memory swapaccount=1 net.ifnames=0"
CMDLINE_NBD="root=/dev/nbd0"
CMDLINE_AOE="root=/dev/etherd/e0.0"
KERNEL_NAMES='s/\(vmlinu[xz]-\)\([^-]*-[^-]*-\)\(.*\)/& \1 \2 \3/p'
INITRD_NAME='s/vmlinu[xz]/initrd.img/p'
KERNEL_PREFIX="vmlinu[z|x]-*"
KERNEL_SUFFIX=""
LIST_KERNELS_64="amd64"
LIST_KERNELS_PAE="686-pae 686-bigmem 686"
LIST_KERNELS_32="586 486 686"
IPAPPEND=2


-- debconf information:
  ltsp-client/abort-installation:

-- debsums errors found:
debsums: changed file /sbin/init-ltsp (from ltsp-client-core package)
debsums: changed file /usr/share/initramfs-tools/scripts/init-premount/udhcp (from ltsp-client-core package)
debsums: changed file /usr/share/ltsp/init-ltsp.d/05-getltsconffile (from ltsp-client-core package)
debsums: changed file /usr/share/ltsp/init-ltsp.d/09-hostname (from ltsp-client-core package)
debsums: changed file /usr/share/ltsp/init-ltsp.d/50-disable-cronjobs (from ltsp-client-core package)
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