Cow Computing

There’s once I was required to setup a limited shell access user account on a commercial hardware product, in which to secure the original system from being modified and at the same time to provide a flexible environment for general work. I was on the way to make use of chroot command. Then i was lucky to came across Jailkit, which saved me a lot of time. So, i would like to use this post to give a little introduction on how to use it.

# First, let's create a directory for the jail account
mkdir /jail
chown root:root /jail

# Then we create a new user account specially for jail account
# *replace <group name>, <username>, <password> with your own value
groupadd <group name>
useradd -d /home/jail -g <group name> -p <password> <username>

# For example, if we only want to allow the jail account to have ssh and basic shell access
jk_init -v -j /jail basicshell ssh

# Then we shall jail the user account we previously created to the jail directory
jk_jailuser -m -j /jail <username>

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Here, i would like to share with you all some commands that is useful in extracting network information from the OS.

1. Extracting IP of the current machine

ifconfig | grep 'inet addr:' | grep -v '127.0.0.1' | cut -d: -f2 | awk '{print $1}'

2. Getting the Gateway of the current machine

route -n | grep 'UG[ \t]' | awk '{print $2}'

3. Updating the network settings

// ifconfig <network interface> <ip> netmask <subnetmask> broadcast <broadcast address>
ifconfig eth0 192.168.0.10 netmask 255.255.255.0 broadcast 192.168.0.255

4. Updating Gateway

// in order to achieve this, we need to first delete the
// existing gateway entry and then add the new one
route del default

// route add -net default gw <gateway address> netmask 0.0.0.0 dev eth0;
route add -net default gw 192.168.0.255 netmask 0.0.0.0 dev eth0