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ubuntu: apt-get install screen
centos/redhat: yum install screen


# screen
# [enter your commands here]

Detach screen:
CTRL+a d

Now you can safely "exit" SSH. Processes keep running.

To re-enter the detached screen:

# screen -x


From within a 'broken' CT enter:

mknod -m 666 /dev/random c 1 8
mknod -m 444 /dev/urandom c 1 9


If this doesn't work....Jimmy Tang listed the minimal set of devices nodes:

mknod -m 600 /dev/console c 5 1
mknod -m 666 /dev/tty c 5 0
mknod -m 666 /dev/full c 1 7
mknod -m 600 /dev/initctl p
mknod -m 666 /dev/null c 1 3
mknod -m 666 /dev/ptmx c 5 2
mkdir /dev/pts
mknod -m 666 /dev/random c 1 8
mknod -m 444 /dev/urandom c 1 9
mknod -m 666 /dev/zero c 1 5


Reference:
http://www.tchpc.tcd.ie/~jtang/blog/posts/Creating_the_minimum_needed_device_nodes_for_openvz/

On a CentOS 5 HN (hardware node) it seems that the server machine itself crashes after making changes in iptables (e.g. with system-config-securitylevel-tui)! The whole machine hangs and becomes unresponsive.
Luckily this doesn't occur when you make changes in iptables from within a VE (virtual environment).



In order to avoid this problem you'll have to stop your OpenVZ services temporarily, make your firewall changes and restart OpenVZ.


# /etc/init.d/vz stop
# system-config-securitylevel-tui
# /etc/init.d/vz start


This problem didn't occur in older kernels but definitely in vzkernel-2.6.18-53.el5.028stab051.1

You can read a threat about this here: http://forum.openvz.org/index.php?t=msg&goto=21273

SSH returns: "Server refused to allocate pty" upon login.
OR:
"enter into VE 101 failed
Unable to open pty: No such file or directory"


This solution is for CentOS VE's.


At the HN (hardware node) enter (replace 101 with your VE-id / CT-id):

# vzctl exec 101 /sbin/MAKEDEV tty
# vzctl exec 101 /sbin/MAKEDEV pty

Then enter the VE/CT:

# vzctl enter 101


And make sure the udev rpm is gone:
# rpm -e --nodeps udev
...else the problem comes back after a VE reboot.

If the problem persists after reboot, repeat the steps above and create the following file within the VE/CT:

/etc/udev/makedev.d/51-udev.nodes

...with these contents:

# These device have to be created manually
tty0
tty1
tty2
tty3
ttyp0
ttyp1
ttyp2
ttyp3
ptyp0
ptyp1
ptyp2
ptyp3


references:

http://forum.openvz.org/index.php?t=msg&goto=14953
http://wiki.openvz.org/Container_enter_failed

Add the following line to file /root/.bashrc

HISTFILE=/root/.bash_history

Now, .bash_history will be created and filled!