User`s guide

Troubleshooting 195
General Considerations
The general issues to take into consideration when troubleshooting your system are listed below.
You should read them carefully before trying to solve more specific problems.
 Make sure a valid license is always loaded on the server. If your license has expired and the
grace period is over, all the virtual machines and Containers on your server will be stopped.
 You should always remember where you are currently located in your terminal. Check it
periodically using the pwd, hostname, ifconfig, cat /proc/vz/veinfo
commands. One and the same command executed inside a virtual machine and Container
and on the server can lead to very different results. You can also set up the PS1 environment
variable to show the full path in the bash prompt. To do this, add these lines to
/root/.bash_profile:
PS1="[\u@\h \w]$ "
export PS1
 If the server slows down, use vmstat, ps (ps axfw), dmesg, top (vztop) to find out
what is happening, never reboot the machine without investigation. If no thinking helps
restore the normal operation, use the Alt+SysRq sequences to dump the memory
(showMem) and processes (showPc).
 If the server was incorrectly brought down, on its next startup all the partitions will be
checked and quota recalculated for each Container, which dramatically increases the startup
time.
 Do not run any binary or script that belongs to a Container directly from the server, for
example, do not ever do that:
cd /vz/root/99/etc/init.d
./httpd status
Any script inside a Container could have been changed to whatever the Container owner
chooses: it could have been trojaned, replaced to something like rm -rf, etc. You can use only
pctl exec/pctl enter to execute programs inside a Container.
 Do not use init scripts on the server. An init script may use killall to stop a service,
which means that all similar processes will be killed in all Containers. You can check
/var/run/Service.pid and kill the correspondent process explicitly.
 You must be able to detect any rootkit inside a Container. It is recommended to use the
chkrootkit package for detection (you can download the latest version from
www.chkrootkit.org), or at least run
rpm -Va|grep "S.5"
to check up if the MD5 sum has changed for any RPM file.
You can also run nmap, for example:
# nmap -p 1-65535 192.168.0.1
Starting nmap V. 2.54BETA22 ( www.insecure.org/nmap/ )
Interesting ports on (192.168.0.1):
(The 65531 ports scanned but not shown below are in
state: closed)
Port State Service
21/tcp open ftp
22/tcp open ssh
80/tcp open http
111/tcp open sunrpc