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# '''vzctl set 101 --userpasswd root:test'''
In this example, we set the root password for Container 101 to "test", and you can log in to the Container via SSH as root and administer it in the same way as you administer a standalone Linux server: install additional software, add users, set up services, and so on. The password will be set inside the Container in the <code>/etc/shadow</code> file in an encrypted form and will not be stored in the Container configuration file. Therefore, if you forget the password, you have to reset it. Note that <code>--userpasswd</code> ignores the <code>--save</code> switch, the password is anyway persistently set for the given Container.
While you can create users and set passwords for them using the <code>vzctl exec</code> or <code>vzctl set</code> commands, it is suggested that you delegate user management to the Container administrator advising him/her of the Container root account password.
Container start in progress...
{{Note|You can also use Container names to start, stop, and restart the corresponding Containers. For detailed information on Container names, please turn to the [[#Setting Name for Container]] section.}}
== Listing Containers ==
103 200000
This shows only running Containers with the information about their IDs and soft limit on disk inodes (see the {{UG/Chapter link|Managing Resources}} chapter for more information), with the list sorted by this soft limit. The full list of the <code>vzlist</code> command line switches and output and sorting options is available in the {{man|vzlist|8}} man page.
== Setting Name for Container ==
# The Container on the Destination Node is started.
'''WARNING: By default, after the migration process is completed, the Container private area and configuration file are deleted on the Source Node!''' However, if you wish the Container private area on the Source Node to not be removed after the successful Container migration, you can override the default <code>vzmigrate</code> behavior by using the <code>–r no</code> switch.
There is a short downtime needed to stop the Container on the Source Node, copy the Container private data changes to the Destination Node, and start the Container on the Destination Node. However, this time is very short and does not usually exceed one minute.
{{Note|For the command to be successful, a direct SSH connection (on port 22) should be allowed between the Source and Destination Nodes.}}
=== Zero-downtime (online) migration ===
You can delete a Container that is not needed anymore with the <code>vzctl destroy ''CTID''</code> command. This command removes the Container private area completely and renames the Container configuration file and action scripts by appending the <code>.destroyed</code> suffix to them.
{{Note|Since vzctl-3.0.24, you can also use the <code>vzctl delete </code> command introduced in Virtuozzo Containers 4.0 to remove Containers from your Hardware Node. This command has the syntax identical to vzctl destroy and is meant to replace the latter in the future.}}
A running Container cannot be destroyed with the <code>vzctl destroy</code> command. The example below illustrates destroying Container 101:
# '''vzctl destroy 101''' Container is currently running. Stop it first. # '''vzctl stop 101''' Stopping container ... Container was stopped Container is unmounted # '''vzctl destroy 101''' Destroying container private area: /vz/private/101 Container private area was destroyed # '''ls /etc/vz/conf/101.*''' /etc/vz/conf/101.conf.destroyed # '''vzctl status 101''' CTID 102 deleted unmounted down If you do not need the backup copy of the Container configuration files (with the .destroyed suffix), you may delete them manually. == Disabling Container ==
In such cases, the OpenVZ software allows you to disable a Container is currently mounted (unmount first), thus, making it impossible to start the Container once it was stopped. For example, you can execute the following command to disable Container 101 residing on your Hardware Node:
# '''vzctl stop set 101--disabled yes --save'''
After the Container was stoppedstopping, the Container user will not be able to start it again until you enable this Container again by passing the <code>--disabled no</code> option to <code>vzctl set</code>. You can also use the <code>--force</code> option to start any disabled Container. For example:
# '''vzctl start 103''' Container start disabled # '''vzctl start 103 --force''' Starting container ... Container is unmountedmounted Adding IP address(es): 192.168.16.3 Setting CPU units: 1000 Configure meminfo: 65536 Container start in progress...
In OpenVZ-based systems, you can use the <code>vzctl chkpnt</code> command to save the current state of a Container private area was destroyed. For example, you can issue the following command to suspend Container 101:
# ls /etc/vz/conf/vzctl chkpnt 101 Setting up checkpoint.*.. suspend... dump... kill... Container is unmounted Checkpointing completed succesfully
== Running Commands in Container ==
Usually, a Container administrator logs in to the Container via network and executes any commands in the Container as on any other Linux box. However, you might need to execute commands inside Containers bypassing the normal login sequence. This can be helpful if:
* You do not know the Container login information, and you need to run some diagnosis commands inside the Container in order to verify that it is operational.
* Network access is absent for a Container. For example, the Container administrator might have accidentally applied incorrect firewalling rules or stopped the SSH daemon.
The OpenVZ software allows you to execute commands in a Container in these cases. Use the <code>vzctl exec</code> command for running a command inside the Container with the given ID. The session below illustrates the situation when the SSH daemon is not started:
# '''vzctl exec 103 /etc/init.d/sshd status'''
openssh-daemon is stopped
# '''vzctl exec 103 /etc/init.d/sshd start'''
Starting sshd: [ OK ]
# '''vzctl exec 103 /etc/init.d/sshd status'''
openssh-daemon (pid 9899) is running...
Now Container users can log in to the Container via SSH (assuming that networking and firewall are not misconfigured).
When executing commands inside a Container from shell scripts, use the <code>vzctl exec2</code> command. It has the same syntax as <code>vzctl exec</code> but returns the exit code of the command being executed instead of the exit code of <code>vzctl</code> itself. You can check the exit code to find out whether the command has completed successfully.
If you wish to execute a command in all running Containers, you can use the following script:
# '''for CT in $(vzlist -H -o ctid); do echo "== CT $CT =="; vzctl exec $CT ''command''; done'''
where ''<code>command</code>'' is the command to be executed in all the running Containers. For example:
# '''for CT in $(vzlist -H -o ctid); do echo "== CT $CT =="; vzctl exec $CT uptime; done'''
== CT 103 ==
15:17:19 up 13 min, 0 users, load average: 0.00, 0.00, 0.00
== CT 123123123 ==
15:17:19 up 22:00, 0 users, load average: 0.00, 0.00, 0.00
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