Slackware template creation

This page is about making a template cache for OpenVZ container from Slackware linux. (This method was used for creating the minimal cache from Slackware 10.2) The method is basically the same as described in article Debian template creation.

Getting a Slackware root filesystem

Downloading and installing Slackware

First you need to download Slackware linux from http://www.slackware.org/getslack/. Then you have to install it to some hardware you can spare while the cache creation process is going on. For container creation it is recommended not to install any unnecessary software into the box you are making the cache from. This means for a minimal Slackware 10.2 cache I have chosen only series A (Base Linux System) at the package series selection screen of Slackware Setup. Then expert prompting mode on the next screen. On the Series A package selection screen I chose the following packages:

• kernel-ide - This is requied to boot the OS to be able to get it's root filesystem
• aaa_base
• aaa_elflibs
• bash
• bin
• bzip2
• coreutils
• cxxlibs
• dcron
• devs
• e2fsprogs - This is not really needed for a container, but let him install it
• elvis
• etc
• gawk
• glibc-solibs
• grep
• gzip
• kernel-modules - This is needed for the first boot only as kernel-ide
• less
• lilo - For first boot only too
• logrotate
• module-init-tools
• openssl-solibs
• pkgtools
• procps
• sed
• shadow
• sysklogd
• sysvinit
• tar
• udev
• util-linux

After selecting these packages just install the kernel and lilo, you are ready to run Slackware!

Configuring Slackware for acting as a container

Now that you have a running minimal Slackware installation, You can begin to prepare it to be a template for a container. First you need some additional packages, 7 exactly:

List of additional packages

Package	Directory of installation media to take the package from
groff-1.19.1-i486-3.tgz	slackware/ap
man-1.5p-i486-1.tgz	slackware/ap
quota-3.12-i486-1.tgz	slackware/ap
iptables-1.3.3-i486-1.tgz	slackware/n
openssh-4.2p1-i486-1.tgz	slackware/n
tcpip-0.17-i486-35.tgz	slackware/n
whois-4.6.16-i486-1.tgz	slackware/n

You can install these packages issuing the following command:

installpkg <packagename>

After these steps, you are ready to move your Slackware installation into a container.

Moving a Slackware installation into a container

I did it by compressing the whole filesystem into a tgz file and copying it to the host running OpenVZ.

Compressing it is easy:

tar --numeric-owner -czf /slackware.tgz --exclude /slackware.tgz /

But to copy it, you need to setup a network device on the slackware system (use ifconfig and ftp) or manually remove the hard drive containing the Slackware installation and copy the tgz file from there.

After you got the tgz file on the host, make a new directory into /vz/private with a new CTID, for example 777. Uncompress the tgz file into this directory and remove the tgz.

mv slackware.tgz /vz/private/777
cd /vz/private/777
gunzip -dc slackware.tgz |tar -xvf -
rm /vz/private/777/slackware.tgz

Preparing the new container

Creating container config

Now you need to create the configuration file for the container, 777.conf:

vzctl set 777 --applyconfig vps.basic --save

Getting the filesystem ready to run in a container

Now you need to make some minor alterations under the /vz/private/777 directory.

Delete the directory /lost+found, clean /boot, /tmp, and /var/mail and make /proc

rm -r /vz/private/777/lost+found
rm /vz/private/777/boot/*
rm /vz/private/777/tmp/*
rm /vz/private/777/var/mail/*
mkdir /vz/private/777/proc

Delete the kernel modules from /lib/modules

rm -r /vz/private/777/lib/modules

Make a home directory for root, readable only by him

mkdir /vz/private/777/root
chmod 0700 /vz/private/777/root

Delete all keys from /etc/ssh

rm /vz/private/777/etc/ssh/*key*

This will ensure that a unique ssh key is generated for every single container at the first boot. Edit ssh_config and sshd_config here if you want.

Delete the file /etc/mtab and make it a symlink to /proc/mounts.

rm /vz/private/777/etc/mtab
ln -s /proc/mounts /vz/private/777/etc/mtab

Clean the /etc/fstab file

echo -n > /vz/private/777/etc/fstab

Edit /etc/inittab

Edit /vz/private/777/etc/inittab, put a hashmark (#) before the lines containing:

c?:1235:respawn:/sbin/agetty 38400 tty? linux

This will prevent linux gettys to spawn.

Edit /etc/shadow

Edit /vz/private/777/etc/shadow, change root's password in the first line to an exclamation mark (!):

root:!:13305:0:::::

This will disable the root login until the password changed with vzctl set CTID --userpasswd root:xxx.

Edit /etc/rc.d/rc.S

Edit /vz/private/777/etc/rc.d/rc.S, putting a hashmark (#) as the first character of the line containing:

/bin/rm -f /etc/mtab*

This should be line 162. This will forbid Slackware to delete our symlink at every reboot.

Edit /etc/rc.d/rc.syslog

Edit /vz/private/777/etc/rc.d/rc.syslog file, put a hashmark (#) before the lines containing

sleep 1
echo "/usr/bin/klogd -c 3 -x"
/usr/bin/klogd -c 3 -x
killall klogd 2> /dev/null

These should be lines 11, 12, 15 and 21. This will prevent klogd (which is usually not needed) from starting at boot time.

Note: if you are going to use iptables rules inside your Slackware containers which will do logging (i.e. the ones with the LOG target), you should not disable klogd.

Testing the new container and making a cache file

Testing the new container

To test the new container, simply start it:

vzctl start 777

If you did everything all right (and this article is correct) your new Slackware container will boot.

If the container booted, and you can enter/ssh to it, then stop it:

vzctl stop 777

Making a cache file

Now make a .tar.gz out of the container:

tar czf /vz/template/cache/slackware-10.2-i486-minimal.tar.gz /vz/private/777/

Testing the new cache file

To test the the new cache file, issue:

vzctl create 555 --ostemplate slackware-10.2-i486-minimal --ipadd x.x.x.x --hostname testy

If created successfully, try to start it:

vzctl start 555

If it started, and you can ssh in, congratulations, you've got a working slackware template!