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openvz interview questions

Top openvz frequently asked interview questions

Private secondary interface on OpenVZ container

I am trying to create a secondary private interface to communicate between 2 openvz containers.

I have tried the steps indicated in the manual here: http://openvz.org/Virtual_Ethernet_device

Doing this I am able to get the container to communicate with the br0 interface I have created on the host machine but the host machine cannot communicate with the container and the containers cannot talk to eachother.

If anyone has experience with this can you share how you accomplished it?


Source: (StackOverflow)

Detect virtualization in bash

One of my commands in my bash script will depend on the virtualization of the server (XEN or OpenVZ or KVM ). How can I check which of these is in use in bash?


Source: (StackOverflow)

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difference between docker and openVZ

I am newbie to world of virtualisation. Can some one explain me what are the differences between openVZ and docker.

What could be good for the future ?

Pros and cons ?


Source: (StackOverflow)

How to clear cache in OpenVZ?

I have OpenVZ VPS and have problem with clearing the cache: enter image description here

In OpenVZ not work echo 3 > /proc/sys/vm/drop_caches enter image description here

How may be this cache clear?


Source: (StackOverflow)

Consumed memory and process memory not match (140MB vs 8MB)

System memory is consumed by ~140MB after running process, but process took only ~8MB. This process (openttd dedicaded server) is completely standalone (does not communicate with others processes).

Before

free -m
             total       used       free     shared    buffers     cached
Mem:          1000        777        222          0          0          0
-/+ buffers/cache:        777        222
Swap:            0          0          0

After

free -m 
             total       used       free     shared    buffers     cached
Mem:          1000        913         86          0          0          0
-/+ buffers/cache:        913         86
Swap:            0          0          0

Process map

pmap 18428 -x
18428:   /var/www/ttd-server/openttd_1.2.3 -s null -m null -x -c /var/www/ttd-server    /configuration/preload/openttd.cfg -D
Address           Kbytes     RSS   Dirty Mode   Mapping
0000000000400000       0    2948       0 r-x--  openttd_1.2.3
0000000000aee000       0      64      48 rw---  openttd_1.2.3
0000000000afe000       0     588     584 rw---    [ anon ]
000000001c66d000       0    2516    2516 rw---    [ anon ]
00002ba83f5a7000       0     100       0 r-x--  ld-2.11.3.so
00002ba83f5c5000       0     256     256 rw---    [ anon ]
00002ba83f7c4000       0       4       4 r----  ld-2.11.3.so
00002ba83f7c5000       0       4       4 rw---  ld-2.11.3.so
00002ba83f7c6000       0       4       4 rw---    [ anon ]
00002ba83f7c7000       0     380       0 r-x--  libstdc++.so.6.0.13
00002ba83f8bd000       0       0       0 -----  libstdc++.so.6.0.13
00002ba83fabd000       0      28      28 r----  libstdc++.so.6.0.13
00002ba83fac4000       0       8       8 rw---  libstdc++.so.6.0.13
00002ba83fac6000       0       4       4 rw---    [ anon ]
00002ba83fadb000       0      52       0 r-x--  libpthread-2.11.3.so
00002ba83faf2000       0       0       0 -----  libpthread-2.11.3.so
00002ba83fcf1000       0       4       4 r----  libpthread-2.11.3.so
00002ba83fcf2000       0       4       4 rw---  libpthread-2.11.3.so
00002ba83fcf3000       0       8       8 rw---    [ anon ]
00002ba83fcf8000       0     112       0 r-x--  libm-2.11.3.so
00002ba83fd78000       0       0       0 -----  libm-2.11.3.so
00002ba83ff78000       0       4       4 r----  libm-2.11.3.so
00002ba83ff79000       0       4       4 rw---  libm-2.11.3.so
00002ba83ff7a000       0     460       0 r-x--  libc-2.11.3.so
00002ba8400d3000       0       0       0 -----  libc-2.11.3.so
00002ba8402d2000       0      16      16 r----  libc-2.11.3.so
00002ba8402d6000       0       4       4 rw---  libc-2.11.3.so
00002ba8402d7000       0      16      16 rw---    [ anon ]
00002ba8402dc000       0      16       0 r-x--  libgcc_s.so.1
00002ba8402f2000       0       0       0 -----  libgcc_s.so.1
00002ba8404f1000       0       4       4 rw---  libgcc_s.so.1
00002ba8404f2000       0     104     104 rw---    [ anon ]
00002ba848565000       0     284     284 rw---    [ anon ]
00007fff900e4000       0      44      44 rw---    [ stack ]
00007fff901fd000       0       8       0 r-x--    [ anon ]
ffffffffff600000       0       0       0 -----    [ anon ]
----------------  ------  ------  ------
total kB          162884    8048    3952

top before (sorted by RES)

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                                         
15801 www-data  17   0 1320m 173m 4036 S  1.3 17.4   0:54.75 java                                                                                                            
 1518 ejabberd  15   0 99684  54m 3724 S  0.0  5.5  18:05.64 beam                                                                                                            
 7917 www-data  15   0  124m  47m 2204 S  0.0  4.8   0:02.43 plackup                                                                                                         
 8039 www-data  15   0  123m  46m 2204 S  0.0  4.7   0:02.38 plackup                                                                                                         
32439 www-data  15   0  116m  42m 2812 S  0.0  4.2   0:42.54 plackup                                                                                                         
29708 mysql     15   0  170m  38m 7556 S  0.0  3.9 187:51.36 mysqld                                                                                                          
32247 www-data  15   0  141m  38m 3376 S  0.0  3.8   0:08.01 plackup                                                                                                         
 6025 www-data  15   0  176m  37m 4532 S  0.0  3.7   0:06.17 php-cgi                                                                                                         
 3248 www-data  15   0  172m  33m 4544 S  0.0  3.4   0:10.55 php-cgi                                                                                                         
 3591 www-data  15   0  123m  32m 3080 S  0.0  3.3   9:09.46 plackup                                                                                                         
32303 www-data  15   0  250m  32m 6364 S  0.3  3.3  17:54.92 mongod                                                                                                          
24324 send2me   16   0 53340  14m 3088 S  0.0  1.5   0:03.00 perl                                                                                                            
26584 bind      25   0 93800  11m 2352 S  0.0  1.1   0:00.17 named                                                                                                           
20045 root      15   0  110m 9288 6876 S  0.0  0.9   2:18.20 ispmgr                                                                                                          
15574 www-data  18   0  144m 9168 5732 S  0.0  0.9   0:00.07 php-cgi                                                                                                         
30220 www-data  15   0 37420 9148 2936 S  0.0  0.9   1:29.11 websockify.py                                                                                                   
 9935 root      16   0 83864 3688 2856 S  0.0  0.4   0:00.02 sshd

top after (sorted by RES):

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                                         
15801 www-data  17   0 1320m 173m 4036 S  1.3 17.4   0:53.77 java                                                                                                            
 1518 ejabberd  15   0 99684  54m 3724 S  0.0  5.5  18:05.62 beam                                                                                                            
 7917 www-data  15   0  124m  47m 2204 S  0.0  4.8   0:02.42 plackup                                                                                                         
 8039 www-data  15   0  123m  46m 2204 S  0.0  4.7   0:02.37 plackup                                                                                                         
32439 www-data  15   0  116m  42m 2812 S  0.0  4.2   0:42.54 plackup                                                                                                         
29708 mysql     15   0  170m  38m 7556 S  0.0  3.9 187:51.34 mysqld                                                                                                          
32247 www-data  15   0  141m  38m 3376 S  0.0  3.8   0:08.01 plackup                                                                                                         
 6025 www-data  15   0  176m  37m 4532 S  0.0  3.7   0:06.17 php-cgi                                                                                                         
 3248 www-data  15   0  172m  33m 4544 S  0.0  3.4   0:10.55 php-cgi                                                                                                         
 3591 www-data  15   0  123m  32m 3080 S  0.0  3.3   9:09.44 plackup                                                                                                         
32303 www-data  15   0  250m  32m 6364 R  0.3  3.3  17:54.61 mongod                                                                                                          
24324 send2me   16   0 53340  14m 3088 S  0.0  1.5   0:03.00 perl                                                                                                            
26584 bind      25   0 93800  11m 2352 S  0.0  1.1   0:00.17 named                                                                                                           
20045 root      15   0  110m 9288 6876 S  0.0  0.9   2:18.19 ispmgr                                                                                                          
15574 www-data  18   0  144m 9168 5732 S  0.0  0.9   0:00.07 php-cgi                                                                                                         
30220 www-data  15   0 37420 9148 2936 S  0.0  0.9   1:29.11 websockify.py                                        

18428 www-data  16   0  151m 8048 4096 R  0.0  0.8   0:00.30 openttd_1.2.3

 9935 root      16   0 83864 3688 2856 S  0.0  0.4   0:00.02 sshd

Looks like virtual memory of process located in physical memory, but why? For example java process have 1320MB of virtual memory but consumed only 173MB of real (mathced with RES), but openttd process have RES=8MB but consumes 136MB of real memory. What this is mean?

UPD.

My server is based on OpenVZ.
Openttd compiled in single threaded mode.
On the real PC there are no problem.

ulimit -a

core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 16382
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 128
cpu time               (seconds, -t) unlimited
max user processes              (-u) unlimited
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

Source: (StackOverflow)

How OpenVZ boot OS?

I bought VPS on OpenVZ virtualization and enabled Debian guest OS.

Guest /boot dir is empty. /etc/inittab is empty.

How is the OS initialization process performed?

What is the meaning of reboot for OpenVZ container?


Source: (StackOverflow)

Unable to connect to MongoDB

I've just installed MongoDB (standard Ubuntu build, not the latest stable) and for some reason I can't connect:

Mon Feb  6 03:11:22 Error: couldn't connect to server 127.0.0.1 shell/mongo.js:79
exception: connect failed

Now my machine isn't 127.x.x.1 it's for some reason x.x.x.2 (But i've changed my config to bind to that address, and also tried to bind to my public IP which provided no avail.

Config:

#mongodb.conf

# Where to store the data.

# Note: if you run mongodb as a non-root user (recommended) you may
# need to create and set permissions for this directory manually,
# e.g., if the parent directory isn't mutable by the mongodb user.
dbpath=/var/lib/mongodb

#where to log
logpath=/var/log/mongodb/mongodb.log

logappend=true

bind_ip = 199.21.114.XX
port = 27017

I've checked the logs and only startup info is displaying in there.

I've also checked that the deamon is running too, and it is - I even tried running it manually with a --fork.

Has anyone come across this before? Or any suggestions?

Thx

UPDATE:

After a restart - here are the logs:

** WARNING: You are running in OpenVZ. This is known to be broken!!!

Tue Feb  7 19:43:32 [initandlisten] db version v1.8.2, pdfile version 4.5
Tue Feb  7 19:43:32 [initandlisten] git version: nogitversion
Tue Feb  7 19:43:32 [initandlisten] build sys info: Linux allspice 2.6.24-28-se$
Tue Feb  7 19:43:32 [initandlisten] *** warning: spider monkey build without ut$
Tue Feb  7 19:43:32 [initandlisten] waiting for connections on port 27017
Tue Feb  7 19:43:32 [websvr] web admin interface listening on port 28017

Source: (StackOverflow)

Clone an OpenVZ system to run locally

I have a VPS on an ISP which is using OpenVZ. I want to run my own image locally to test some services, but I can only download a tar backup of the filesystem.

Can I create a image and run it locally using the tar backup ? I'm on Windows 7. Maybe VMWare Player or Oracle VirtualBox can run this files ?


Source: (StackOverflow)

Install Docker on OpenVZ VPS

I have a OpenVZ VPS, the operating system is CentOS 6, I try to install Docker, but Docker start error.

Starting cgconfig service: Error: cannot mount cpuset to /cgroup/cpuset: Invalid argument
/sbin/cgconfigparser; error loading /etc/cgconfig.conf: Cgroup mounting failed
Failed to parse /etc/cgconfig.conf or /etc/cgconfig.d      [FAILED]
Starting docker:                                           [  OK  ]

Source: (StackOverflow)

Cmt migration tool validation error

I am using cmt (https://github.com/marcosnils/cmt) for container migration and I have problem in the validation.

# cmt validate --src `pwd` --dst walid@192.168.1.12

2016/01/11 17:31:53 Error criu does not exist in dst

I am sure both have the patched version of criu (https://github.com/marcosnils/criu) on both servers.

And I even tried it the other way around with the same result.


Source: (StackOverflow)

MongoDB in OpenVZ VPS

There are some discussions about the problem associated with MongoDB caching in OpenVZ, I was unable to find a practical solution. The issue is related to the memory in OpenVZ, as MongoDB does not consume free memory only. I tried to limit virtual memory by ulimit command, but the problem is that MongoDB server will shut down when reading the limit value of virtual memory (if using unlimited virtual memory, it will shut down when consuming all the machine ram).


Source: (StackOverflow)

/proc/user_beancounter how to perform monitoring

I want to perform monitoring of /proc/user_beancounters to see when the system hits the limits and what process is to blame.

Does anybody know tools for this issue?


Source: (StackOverflow)

aerospike on openvz 2core 4Gb ram doesn't start and doesn't give errors

after installation without any trouble I've started aerospike on a openvz vps with 2cores and 4gb ram. this is the result:

root@outland:~# /etc/init.d/aerospike start
 * Start aerospike:  asd  [OK]

then check for running asd:

root@outland:~# /etc/init.d/aerospike status
 * Halt aerospike:  asd                                                  [fail]

what is going wrong?

adding logs:

Mar 03 2015 15:17:57 GMT: INFO (config): (cfg.c::3033) system file descriptor limit: 100000, proto-fd-max: 15000

Mar 03 2015 15:17:57 GMT: WARNING (cf:misc): (id.c::249) Tried eth,bond,wlan and list of all available interfaces on device.Failed to retrieve physical address with errno 19 No such device


Mar 03 2015 15:17:57 GMT: CRITICAL (config): (cfg.c:3363) could not get unique id and/or ip address

Mar 03 2015 15:17:57 GMT: WARNING (as): (signal.c::120) SIGINT received, shutting down

Mar 03 2015 15:17:57 GMT: WARNING (as): (signal.c::123) startup was not complete, exiting immediately

Source: (StackOverflow)

Default traffic shaping rules for OpenVZ in CentOS 6

I have the following configuration:

  • OpenVZ host running CentOS 6 (2.6.32-042stab049.6), gigabit connection
  • A single container running on that OpenVZ

The host has full gigabit connection for in- and outbound connections. The containers have full gigabit for all outgoing traffic, but incoming traffic seems subject to a default traffic shaping rules where "bursts" are allowed. Downloading large binary files happens at 15MB/s for a few seconds, then it falls back to 50Kb/s.

That very same file can be downloaded on the host at full speed, over and over again.

Traffic shaping isn't enabled:

root@host:~# tc qdisc show dev venet0
root@host:~# tc class show dev venet0
root@host:~# tc filter show dev venet0

IPtables has nothing fancy:

root@host:~# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination   
Chain FORWARD (policy ACCEPT)
target     prot opt source               destination   
Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

I'm actually finding myself a bit stuck and am considering this may just be a bug in the OpenVZ kernel for CentOS 6. I don't have the option to test it on CentOS 5 in the near future. Does anyone have any other ideas on how to troubleshoot? Or does it sound familiar? Given the fact that the host runs just find and only the CT's have the incoming bandwidth issue, I'm looking at OpenVZ as the cause.


Source: (StackOverflow)

MongoDB in Virtuozzo (OpenVZ)

My Server is hosted on HostEurope, a virtual server

uname -a prompts

Linux lvps176-28-21-237.dedicated.hosteurope.de 2.6.18-028stab095.1 #1 SMP Mon Oct 24 20:15:15 MSD 2011 x86_64 GNU/Linux

They are running OpenVZ. According to the support of HostEurope, an up to date version of Virtuozzo, but reading the version history on OpenVZ, this version is old, frozen and won't be maintained any more. Who is right?

My actual problem is that I want to run a MongoDB, but I am confronted with this OpenVZ problem explained here:

Crashes reported on OpenVZ

So, what can I do? Is there any chance to solve this Out-Of-Memory issue in MongoDB on OpenVZ in this version or do I have to find an other hosting company?

Thanks!


Source: (StackOverflow)