From: Jacques Gelinas (jack_at_solucorp.qc.ca)
Date: Tue 15 Oct 2002 - 04:38:38 BST
1.1. /usr/lib/vserver/vcheck: new
The vcheck utility has been created to verify package integrity in one
vserver using the package database of another server. This is a first
step to create a Linux server where one can answer the following
+ Has this server been cracked ?
+ What was changed ?
Currently, there is no Linux distribution (no OS in fact) which may
answer those questions. Once a server has been abused, the intruder
may have changed quite a lot and may have cover his tracks. When you
execute a command on such a machine, you can't really trust the
Now, on a linux server running vservers and no network service in the
root server, you have one part of the solution. The root server and
the kernel can't be tempered. So you can always trust the various
commands you are running.
Now proving that along its entire life, the root server has never been
opened to crack attempt, is a difficult project. All I say is that a
root vserver can't be modified from the vservers or anywhere else if
it has no network service.
This is nevertheless one goal of the vserver project. Create a robust
and trusted root server in which you can run all kind of more flexible
Back to our normal schedule...
So if you trust the root server and you trust another (reference)
vserver (one which is never running), you can use the vcheck utility
to perform an rpm verify command, but using the RPM database in the
reference vserver. The corresponding packages will be checked.
vcheck --verify refvserver vserver1 vserver2 ...
vcheck has another option, --diffpkgs, to compare the package list in
to vserver. You can see how to vservers evolved.
1.2. Argument quoting part 2
The vserver command was discarding argument topology. A fix was done
in 0.20, but it was flawed. Now it should work fine. You can do
/usr/sbin/vserver server exec command "argument with space"
And the command will receive a single argument.
1.3. GCC 3.2 support
The various little fixes have been added so the project compiles
properly using GCC 3.2.
1.4. newvserver enhancements
Two section has been added to the dialog. One is "authentication". It
lets you enter the vserver root password, select if you want MD5
passwords and shadow passwords.
The other section is called NIS/Ldap. It lets you enter the NIS
domain, NIS server, LDAP base dn and LDAP server.
Both section are normally found at the end of the installation of a
This information is enabled in the vserver using the authconfig
command. Not all distribution carry this command. We will have to
figure out how to enable this on all distribution. If
/usr/sbin/authconfig is missing in the vserver, the information is not
applied. So newvserver works anyway.
1.5. newvserver: installing from mandrake 8.2 and redhat 8.0
I have modified newvserver to install from those OS. Mandrake 8.2 does
not work yet (work in progress). Not sure why. RedHat 8.0 kind of
work. The problem is really weird. When I execute the following script
on RedHat 8.0, to install a Redhat 8.0 vserver newvserver do:
/usr/lib/vserver/install-rh8.0 redhat full
Now, if you run this with the Redhat supplied kernel (2.4.18-14), it
works. If you use a 2.4.19 kernel (2.4.19ctx-14 for example), rpm
installs few package and then wait forever, trapped in a pause()
I have not yet explain this behavior.
1.6. rebootmgr using pidfile
The rebootmgr service now uses a PID file to locate the process. This
makes the system V init script more reliable. The script itself does
not include the "function" helper script anymore. This is a redhat-ism
and it was not using it anyway.
1.7. vserver --nodev option
Sometime, you wish to enter a vserver without enabling its network
device. You often need this because the vserver is a copy and the real
vserver is already running on another physical server. Enabling the
device would cause clashes on the network.
The --nodev option tells vserver not to skip this step.
/usr/sbin/vserver --nodev server enter
1.8. vserver: vlan support
A vserver may be installed on an IP number sitting on a different vlan
(Virtual LAN). You specify the IPROOTDEV has device.vlannum (eth0.231)
or the IPROOT using device.vlannum:IP.
An IP alias will be set on this virtual device after configuring it.
It uses the loopback number as the default IP to configure the vlan
2. Bug fixes
2.1. capchroot: incompatible NSS plug-gins
capchroot is used to cross the vserver root and then select the proper
UID to execute the command. Unfortunately, this program is started in
the root server environment, then switch the root and then uses
getpwnam to learn about the user ID of a named user.
to perform the getpwnam() call, glibc uses NSS (Name Service Switch)
plug-gins to access the user information. These plug-gins are taken in
the vserver environment and are not always compatible with the root
To avoid this problem, we really need two utilities. One running in
the root server, switching root and then calling another (/bin/id ?)
in the vserver to learn about the user. This way, both utilities will
be compatible with each world. Remember that a root server may be some
Linux distribution/release and the vserver may be running a totally
For now, I have fixed the problem somewhat, but it is not perfect
Before switching root, I perform a getpwnam("root"), so the plug-gins
are loaded. When I perform the real getpwnam, after the switch, the
plug-gins are already in memory so they work. Further, if the target
user is root, I do not need to perform any of this and uses the UID 0.
Note that this capchroot feature is needed by the suexec sub-command
of the vserver command.
This cheat kind of works. It works for most people. Now, if your
vserver is running NIS and not your root server, for example, then the
NSS plug-gins loaded are not the one needed in the vserver. In this
case it does not work.
We will need a better solution. For now, what we have will work for
pretty much everybody.
2.2. Stopping a vserver on debian
The vserver script was not setting the PREVLEVEL environment variable
before switching to runlevel 6. This has the effect of not stopping
the services properly.
Jacques Gelinas <jack_at_solucorp.qc.ca>
vserver: run general purpose virtual servers on one box, full speed!