[Pkg-ltsp-devel] Bug#422962: ltsp-server: Using nbdswapd script leaves unused processes and swap files on server

[Bryan Sutula]

Package: ltsp-server
Version: 0.99debian11
Severity: normal

I am trying to use NBD swap to compensate for a client with little memory.

Following the brief instructions in the /usr/share/doc/ltsp-server/swap
file, I find that when the client crashes, the two swap processes on the
server:

nobody   15730  4777  0 17:20 ?        00:00:00 /bin/sh /usr/sbin/nbdswapd
nobody   15739 15730  0 17:20 ?        00:00:00 /bin/nbd-server

as well as the swap file itself are left lying around.  If the client is
rebooted, new processes and a new swap file are used.  If this process
repeats, there gets to be a lot of these dead processes and swap files.

I explored adding options to /etc/ltsp/nbdswapd.conf:

NBD_SERVER_OPTS="-a 300"

Of course, a longer time can be used.  This does kill the nbd-server and
shell script process, as well as delete the swap file.  However, the
system administrator is left trying to figure out how long to set the
time.  By experimentation, if the system is left idle for longer than the
set time, the swap file will close and the client will be in a bad
situation.  So one would have to set this time very long (days or weeks),
and of course, that would defeat the whole purpose of the setting.  Also,
no matter how long it's set for, it seems that Linux won't necessarily
use swap unless it needs it, and since the goal is that it's almost
never needed for an LTSP application, a timeout is not a good solution.

I will experiment with the latter half of the "swap" instruction file,
where the swap daemon is tied to an IP address.  This seems more likely
to work.  But why couldn't the shell script use a similar technique
(based on IP address or something like that).  It seems that the first-
suggested approach is problematic and shouldn't be recommended, or the
script should work differently.

Sorry for tacking other issues onto this, but also noticed along the
way is that the package puts it's main ltsp.conf configuration file in
/etc (no subdirectory) which is legal, but when the user wants to
configure nbdswapd, they must create an /etc/ltsp directory and add a
new config file there.  I suggest having the ltsp-server package create
/etc/ltsp from the start and drop it's ltsp.conf file there.

-- Package-specific info:
packages in chroot: /opt/ltsp/i386
ii  initramfs-tools          0.85g                    tools for generating an initramfs
ii  ldm                      0.99debian11             LTSP display manager
ii  ltsp-client              0.99debian11             LTSP client environment

-- System Information:
Debian Release: 4.0
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.18-4-686
Locale: LANG=en_US, LC_CTYPE=en_US (charmap=ISO-8859-1)

Versions of packages ltsp-server depends on:
ii  debconf [debconf-2.0]       1.5.11       Debian configuration management sy
ii  debconf-utils               1.5.11       debconf utilities
ii  debootstrap                 0.3.3.2      Bootstrap a basic Debian system
ii  esound-clients              0.2.36-3     Enlightened Sound Daemon - clients
ii  gettext-base                0.16.1-1     GNU Internationalization utilities
ii  iproute                     20061002-3   Professional tools to control the 
ii  lsb-release                 3.1-23.1     Linux Standard Base version report
ii  nfs-kernel-server           1:1.0.10-6   Kernel NFS server support
ii  openbsd-inetd [inet-superse 0.20050402-6 The OpenBSD Internet Superserver
ii  openssh-client              1:4.3p2-9    Secure shell client, an rlogin/rsh
ii  python                      2.4.4-2      An interactive high-level object-o
ii  ssh                         1:4.3p2-9    Secure shell client and server (tr
ii  tcpd                        7.6.dbs-13   Wietse Venema's TCP wrapper utilit
ii  tftpd-hpa                   0.43-1.1     HPA's tftp server
ii  update-inetd                4.27-0.5     inetd.conf updater

Versions of packages ltsp-server recommends:
ii  nbd-server                    1:2.8.7-4  the Network Block Device server
ii  openssh-server                1:4.3p2-9  Secure shell server, an rshd repla
ii  ssh                           1:4.3p2-9  Secure shell client and server (tr

-- debconf information excluded