4.3. Managing Processes and Services

In Virtuozzo, services and processes can be managed using the following command-line utilities:

  • vzps
  • vzpid
  • vztop

With their help, you can perform the following tasks:

  • print the information about active processes on your hardware node,
  • view the processes activity in real time,
  • change the mode of the services that can be either xinetd-dependent or standalone,
  • identify the container UUID where a process is running by the process ID.

Note

The maximum number of processes per container is limited to 131,072.

4.3.1. Viewing Active Processes and Services

The vzps utility provides certain additional functionality related to monitoring separate containers running on the hardware node. For example, you can use the -E switch with the vzps utility to:

  • display the container UUIDs where the processes are running
  • view the processes running inside a particular container

vzps prints the information about active processes on your hardware node. When run without any options, vzps lists only those processes that are running on the current terminal. Below is an example output of vzps:

# vzps
  PID TTY         TIME CMD
 4684 pts/1   00:00:00 bash
27107 pts/1   00:00:00 vzps

Currently, the only processes assigned to the user/terminal are the bash shell and the vzps command itself. In the output, the PID (Process ID), TTY, TIME, and CMD fields are contained. TTY denotes which terminal the process is running on, TIME shows how much CPU time the process has used, and CMD is the name of the command that started the process.

Note

The IDs of the processes running inside containers and displayed by running the vzps command on the hardware node does not coincide with the IDs of the same processes shown by running the ps command inside these containers.

As you can see, the standard vzps command just lists the basics. To get more details about the processes running on your server, you will need to pass some command line arguments to vzps. For example, using the aux arguments with this command displays processes started by other users (a), processes with no terminal or one different from yours (x), the user who started the process and when it began (u).

# vzps aux
USER  PID %CPU %MEM   VSZ  RSS TTY   STAT START  TIME COMMAND
root    1  0.0  0.0  1516  128 ?     S   Jul14   0:37 init
root    5  0.0  0.0     0    0 ?     S   Jul14   0:03 [ubstatd]
root    6  0.0  0.0     0    0 ?     S   Jul14   3:20 [kswapd]
#27     7  0.0  0.0     0    0 ?     S   Jul14   0:00 [bdflush]
root    9  0.0  0.0     0    0 ?     S   Jul14   0:00 [kinoded]
root 1574  0.0  0.1   218  140 pts/4 S   09:30   0:00 -bash

There is a lot more information now. The fields USER, %CPU, %MEM, VSZ, RSS, STAT, and START have been added. Let us take a quick look at what they tell us.

The USER field shows you which user initiated the command. Many processes begin at system start time and often list root or some system account as the user. Other processes are, of course, run by actual users.

The %CPU, %MEM, VSZ, and RSS fields all deal with system resources. First, you can see what percentage of the CPU the process is currently utilizing. Along with CPU utilization, you can see the current memory utilization and its VSZ (virtual memory size) and RSS (resident set size). VSZ is the amount of memory the program would take up if it were all in memory. RSS is the actual amount currently in memory. Knowing how much a process is currently eating will help determine if it is acting normally or has spun out of control.

You will notice a question mark in most of the TTY fields in the vzps aux output. This is because most of these programs were started at boot time and/or by initialization scripts. The controlling terminal does not exist for these processes; thus, the question mark. On the other hand, the bash command has a TTY value of pts/4. This is a command being run from a remote connection and has a terminal associated with it. This information is helpful for you when you have more than one connection open to the machine and want to determine which window a command is running in.

STAT shows the current status of a process. In our example, many are sleeping, indicated by an S in the STAT field. This simply means that they are waiting for something. It could be user input or the availability of system resources. The other most common status is R, meaning that it is currently running.

You can also use the vzps command to view the processes inside any running container. The example below shows you how to display all active processes inside the container MyCT with UUID 26bc47f6-353f-444b-bc35-b634a88dbbcc:

# vzps -E 26bc47f6-353f-444b-bc35-b634a88dbbcc
                                CTID     PID TTY          TIME CMD
26bc47f6-353f-444b-bc35-b634a88dbbcc   14663 ?        00:00:00 init
26bc47f6-353f-444b-bc35-b634a88dbbcc   14675 ?        00:00:00 kthreadd/26bc47
26bc47f6-353f-444b-bc35-b634a88dbbcc   14676 ?        00:00:00 khelper
26bc47f6-353f-444b-bc35-b634a88dbbcc   14797 ?        00:00:00 udevd
26bc47f6-353f-444b-bc35-b634a88dbbcc   15048 ?        00:00:00 rsyslogd
26bc47f6-353f-444b-bc35-b634a88dbbcc   15080 ?        00:00:00 sshd
26bc47f6-353f-444b-bc35-b634a88dbbcc   15088 ?        00:00:00 xinetd
26bc47f6-353f-444b-bc35-b634a88dbbcc   15097 ?        00:00:00 saslauthd
26bc47f6-353f-444b-bc35-b634a88dbbcc   15098 ?        00:00:00 saslauthd
26bc47f6-353f-444b-bc35-b634a88dbbcc   15116 ?        00:00:00 sendmail
26bc47f6-353f-444b-bc35-b634a88dbbcc   15125 ?        00:00:00 sendmail
26bc47f6-353f-444b-bc35-b634a88dbbcc   15134 ?        00:00:00 httpd
26bc47f6-353f-444b-bc35-b634a88dbbcc   15139 ?        00:00:00 httpd
26bc47f6-353f-444b-bc35-b634a88dbbcc   15144 ?        00:00:00 crond
26bc47f6-353f-444b-bc35-b634a88dbbcc   15151 ?        00:00:00 mingetty
26bc47f6-353f-444b-bc35-b634a88dbbcc   15152 ?        00:00:00 mingetty

4.3.2. Monitoring Processes in Real Time

The vztop utility is rather similar to vzps but is usually started full-screen and updates continuously with process information. This can help with programs that may infrequently cause problems and can be hard to see with vzps. Overall system information is also presented, which makes a nice place to start looking for problems.

The vztop utility can be used just as the standard Linux htop utility. It shows a dynamic list of all processes running on the system with their full command lines.

By default, it shows information about processor, swap and memory usage, number of tasks, load average, and uptime at the top of the screen. You can change the default meters, along with display options, color schemes, and columns at the setup screen (S or F2).

vztop can be used interactively for sending signals to processes. For example, you can kill processes—without knowing their PIDs—by selecting them and pressing F9. You can also change process priority by pressing F7 (increase; can only be done by the root user) and F8 (decrease).

The vztop utility usually has an output like the following:

# vztop
1  [                                            0.0%]  Tasks: 77, 65 thr; 1 running
2  [|||                                         2.6%]  Load average: 0.02 0.03 0.05
3  [||||                                        4.6%]  Uptime: 06:46:48
4  [|                                           0.7%]
Mem[|||||||||||||||||||||                 344M/3.68G]
Swp[                                        0K/3.87G]

PID CTID USER  PRI NI VIRT   RES   SHR S CPU% MEM%  TIME+  Command
1     0  root  20  0 41620  4132  2368 S 0.0  0.1  0:05.91 /usr/lib/systemd/systemd
3164  0  root  20  0 19980  1380  1160 S 0.0  0.0  0:00.32 /usr/1ib/systemd/systemd-
3163  0  root  21  1 1402M 56992 10204 S 0.0  1.5  4:12.41 /usr/libexec/qemu-kvm -na
3186  0  root  20  0 1402M 56992 10204 S 0.0  1.5  0:00.09 /usr/libexec/qemu-kvm -na
3185  0  root  20  0 1402M 56992 10204 S 0.7  1.5  2:16.83 /usr/libexec/qemu-kvm -na
3180  0  root  20  0 1402M 56992 10204 S 0.0  1.5  0:00.00 /usr/libexec/qemu-kvm -na
3084  0  smmsp 20  0 85712  2036   516 S 0.0  0.1  0:00.19 sendmail: Queue runner@01
3064  0  root  20  0   98M  2380   572 S 0.0  0.1  0:01.43 sendmail: accepting conne
3036  0  root  20  0  291M  4788  3580 S 0.0  0.1  0:00.00 /usr/sbin/virt1ogd
3037  0  root  20  0  291M  4788  3580 S 0.0  0.1  0:00.00 /usr/sbin/virt1ogd
2787  0  nobody20  0 15548   896   704 S 0.0  0.0  0:00.14 /sbin/dnsmasq --conf-file
2788  0  root  20  0 15520   184     0 S 0.0  0.0  0:00.00 /sbin/dnsmasq --conf-file
2479  0  root  20  0 1962M 33344 24160 S 0.7  0.9  3:13.12 /usr/sbin/pr1_disp_servic
9022  0  root  20  0 1962M 33344 24160 S 0.0  0.9  0:10.74 /usr/sbin/pr1_disp_servic

The column CTID shows the container UUID inside which the process is running (the value 0 means that the process is running on the server), PRI (PRIORITY) displays the kernel’s internal priority for the process, and NI (NICE) shows the nice value (the nicer the process, the more it lets other processes take priority).

To organize processes by parenthood, you can switch to the tree view by pressing F5.

4.3.3. Determining Container UUIDs by Process IDs

Each process is identified by a unique PID (process identifier), which is the entry of that process in the kernel’s process table. For example, when you start Apache, it is assigned a process ID. This PID is then used to monitor and control this program. The PID is always a positive integer. In Virtuozzo, you can use the vzpid (retrieve process ID) utility to print the container UUID the process with the given id belongs to. Multiple process IDs can be specified as arguments. In this case the utility will print the container number for each of the processes.

The typical output of the vzpid utility is shown below:

# vzpid 14663
Pid               VEID    Name
14663     26bc47f6-...    init

Note

You can also display the container UUID where the corresponding process is running by using the vzps utility.