{"id":5199,"date":"2022-05-29T11:39:52","date_gmt":"2022-05-29T14:39:52","guid":{"rendered":"https:\/\/blog.clusterweb.com.br\/?p=5199"},"modified":"2022-05-29T11:39:52","modified_gmt":"2022-05-29T14:39:52","slug":"how-to-let-linux-scripts-detect-theyre-running-in-virtual-machines","status":"publish","type":"post","link":"https:\/\/blog.clusterweb.com.br\/?p=5199","title":{"rendered":"How to Let Linux Scripts Detect They\u2019re Running in Virtual Machines"},"content":{"rendered":"
\"Two<\/figure>\n

 <\/p>\n

Virtual machines\u00a0try really hard to convince their\u00a0operating systems\u00a0that they\u2019re running on physical hardware. So can you tell from\u00a0the Linux command line\u00a0if the computer is physical or virtual?<\/figure>\n
<\/div>\n

Virtual Machines and Hypervisors<\/h2>\n

A traditional computer is a physical object. It\u2019s a collection of different pieces of hardware that are plugged and bolted together so that you can load an operating system, install applications, launch them, and use them.<\/p>\n

Hardware is expensive.\u00a0Being restricted to one operating system per physical computer means the cost of running several operating systems soon becomes prohibitive. A better solution would be to allow a single physical computer to run a selection of operating systems at the same time, with each one thinking it\u2019s running in its own, unique hardware.<\/p>\n

\n
A hypervisor\u00a0makes this possible. A hypervisor\u2014also called a virtual machine manager or virtual machine monitor\u2014is software that lets you create virtual machines. These behave as though they were individual, physical computers although they run on the same physical host, sharing its hard drive space, memory, and\u00a0CPU cores.<\/div>\n<\/div>\n

Of course, the host computer has to be powerful enough to cope with the demands of the collection of virtual machines, but, given sufficient\u00a0RAM\u00a0and processing power in the host, virtual machines can run at near bare-metal speeds.<\/p>\n

Since the release of the 2.6.20 kernel in 2007, Linux has had\u00a0K<\/strong>ernel-based\u00a0V<\/strong>irtual\u00a0M<\/strong>achine support baked right in. Linux has several hypervisors available to it, such as\u00a0VirtualBox,\u00a0GNOME Boxes, and\u00a0QEMU-KVM. They make use of the native KVM capability of Linux, building upon the native kernel functionality by adding user interfaces and functionality such as being able to\u00a0take a snapshot\u00a0of a virtual machine.<\/p>\n

Virtual machines bring cost savings, efficiencies, simplified deployments, and\u2014provisioned correctly\u2014security benefits. They also facilitate scalability. New servers can be automatically spun up as demand for a service increases and shut down when demand drops. This makes them hugely popular both in the cloud and in on-premise infrastructure.<\/p>\n

Perhaps you\u2019re\u00a0remotely administering a Linux server\u00a0and you need to know whether it is a virtual machine or a physical box. Or you have a\u00a0script\u00a0that needs to know what type of platform it is executing on. Here are several ways you can detect if the computer you\u2019re working on is physical or virtual.<\/p>\n

<\/p>\n

The dmidecode Command<\/h2>\n

The\u00a0dmidecode<\/code>\u00a0command supports a large number of options and modifiers. It interrogates the Desktop Management Interface (DMI) tables, and prints the information in the terminal window.<\/p>\n

\n
We\u2019ll use it with the -s<\/code>\u00a0(display a single string) option, and ask for the system product name. Note that we must use\u00a0sudo<\/code>.<\/div>\n<\/div>\n

We\u2019ll run the command on a VirtualBox VM running Ubuntu 22.04.<\/p>\n

\n
\n
\n
<\/div>\n
sudo dmidecode -s system-product-name<\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n

\"The<\/p>\n

The platform is correctly identified as VirtualBox.<\/p>\n

On a QEMU-KVM VM running\u00a0Fedora 35, we get this output.<\/p>\n

sudo dmidecode -s system-product-name<\/pre>\n
\"The<\/p>\n
Although this is reported as a standard PC, it is a standard QEMU virtual PC, of type Q35. So the platform is correctly recognized as a virtual machine.<\/p>\n
If we run the same command on a physical computer we get some information about the manufacturer.<\/p>\n
sudo dmidecode -s system-product-name<\/pre>\n
\"The<\/p>\n
This computer is a custom-build based on a Micro-Star International Company Limited motherboard, with the product code of MS-7B86.<\/p>\n
The lshw Command<\/h2>\n
The\u00a0lshw<\/code>\u00a0command\u00a0lists the details for a wide range of computer hardware. We can choose which class of hardware we want\u00a0lshw<\/code>\u00a0to report on.<\/p>\n
\n
We\u2019re going to use the -class<\/code>\u00a0option with the\u00a0system<\/code>\u00a0modifier. Using\u00a0sudo<\/code>\u00a0with this command ensures we see all of the detail.<\/div>\n<\/div>\n
We\u2019ll run this command on our Ubuntu VirtualBox VM.<\/p>\n
sudo lshw -class system<\/pre>\n
\"The<\/p>\n
    \n
  • The \u201cdescription\u201d field has a generic entry of \u201ccomputer.\u201d<\/li>\n
  • The \u201cproduct\u201d field tells us this is a virtual machine running in VirtualBox.<\/li>\n
  • The \u201cvendor\u201d field contains the name of the German company that created VirtualBox, Innotek GmbH. Innotek was acquired by the Oracle Corporation in 2010 as part of its acquisition of Sun Microsystems, Inc.<\/li>\n<\/ul>\n
    We had to install\u00a0lshw<\/code>\u00a0on Fedora.<\/p>\n
    sudo dnf install lshw<\/pre>\n
    \"Installing<\/p>\n
    Let\u2019s try that command in our Fedora VM running in GNOME Boxes.<\/p>\n
    sudo lshw -class system<\/pre>\n
    \"The<\/p>\n
      \n
    • Again, the \u201cdescription\u201d field has a generic entry of \u201ccomputer.\u201d<\/li>\n
    • The \u201cproduct\u201d field gives us the same standard QEMU PC information that we saw with the\u00a0dmidecode<\/code>\u00a0command.<\/li>\n
    • The \u201cvendor\u201d field contains \u201cQEMU\u201d which quite clearly indicates this is a virtual machine.<\/li>\n<\/ul>\n
      This is the result of running the same command on our physical computer.<\/p>\n
      sudo lshw -class system<\/pre>\n
      \"The<\/p>\n
      We can see that this is a hardware computer, with a Micro-Star\u00a0motherboard.<\/p>\n
        \n
      • The hardware is identified as a desktop computer.<\/li>\n
      • The \u201cproduct\u201d field gives us the motherboard type, MS-7B86.<\/li>\n
      • The \u201cvendor\u201d field contains the manufacturer\u2019s name.<\/li>\n<\/ul>\n
        The hostnamectl Command<\/h2>\n
        This command has the advantage that you don\u2019t need to have\u00a0sudo<\/code>\u00a0privileges to run it. However, it is only available on\u00a0systemd<\/code>-enabled distributions. The majority of modern distributions\u00a0use\u00a0systemd<\/code>.<\/p>\n
        This is the response from running the command on our Ubuntu VirtualBox VM.<\/p>\n
        hostnamectl<\/pre>\n
        \"The<\/p>\n
          \n
        • The \u201cicon-name\u201d field has \u201c-vm\u201d appended to it.<\/li>\n
        • The \u201cChassis\u201d field contains \u201cvm.\u201d<\/li>\n
        • The \u201cVirtualization\u201d field contains \u201coracle.\u201d<\/li>\n
        • The \u201cHardware Vendor\u201d field contains \u201cinnotek GmbH.\u201d<\/li>\n
        • The \u201cHardware Model\u201d field contains \u201cVirtualBox.\u201d<\/li>\n<\/ul>\n
          The output on our Fedora VM inside GNOME Boxes is very similar.<\/p>\n
          hostnamectl<\/pre>\n
          \"The<\/p>\n
            \n
          • The \u201cicon-name\u201d field has \u201c-vm\u201d appended to it.<\/li>\n
          • The \u201cChassis\u201d field contains \u201cvm.\u201d<\/li>\n
          • The \u201cVirtualization\u201d field contains \u201ckvm.\u201d<\/li>\n
          • The \u201cHardware Vendor\u201d field contains \u201cQEMU\u201d<\/li>\n
          • The \u201cHardware Model\u201d field contains \u201cStandard PC (Q35 + ICH9, 2009).\u201d<\/li>\n<\/ul>\n
            If we use the hostnamectl command on our physical desktop, the output doesn\u2019t contain a \u201cVirtualization\u201d line.<\/p>\n
            hostnamectl<\/pre>\n
            \"The<\/p>\n
            If there\u2019s no \u201cVirtualization\u201d field, you must be running on bare metal.<\/p>\n
            The systemd-detect-virt Command<\/h2>\n
            If you want to get as short an answer as possible,\u00a0systemd-detect-virt<\/code>\u00a0is probably what you\u2019re looking for. Again this requires a\u00a0systemd<\/code>-equipped distribution, but it doesn\u2019t require\u00a0sudo\u00a0<\/code>privileges. This\u2014and its terse output\u2014make it well suited for use in scripts.<\/p>\n
            This is the result of running the command on our Ubuntu VirtualBox VM.<\/p>\n
            systemd-detect-virt<\/pre>\n
            \"Identifying<\/p>\n
            Our copy of Fedora running in GNOME Boxes is reported as using KVM virtualization.<\/p>\n
            systemd-detect-virt<\/pre>\n
            \"Identifying<\/p>\n
            Running\u00a0systemd-detect-virt<\/code>\u00a0on our hardware machine results in \u201cnone\u201d being printed to the terminal.<\/p>\n
            systemd-detect-virt<\/pre>\n
            \"A<\/p>\n
            A Platform-Sensitive Script<\/h2>\n
            To give a script the ability to detect whether it is running in a virtualized environment or on physical hardware, we can use the\u00a0systemd-detect-virt<\/code>\u00a0command and use\u00a0Bash\u00a0case<\/code>\u00a0statements\u00a0to handle the options.<\/p>\n
            This is the script we\u2019ll use. Copy this text and save it into a file called \u201cplatform.sh.\u201d<\/p>\n
            #!\/bin\/bash\r\n\r\nshopt -s nocasematch\r\n\r\ncase $(systemd-detect-virt) in\r\n\r\n  none)\r\n    echo \"Physical Hardware\"\r\n    ;;\r\n\r\n  *)\r\n    echo \"Virtual Machine\"\r\n    ;;\r\nesac<\/pre>\n
            The script\u00a0uses\u00a0shopt<\/code>\u00a0to choose case-insensitive matching. The\u00a0systemd-detect-virt<\/code>\u00a0command is used in the\u00a0case<\/code>\u00a0statement. The output from this command is compared with each of the\u00a0case<\/code>\u00a0clauses in the body of the\u00a0case<\/code>\u00a0statement until a match is found.\u00a0Anything that isn\u2019t matched is captured by the \u201c*)\u201d default clause.<\/p>\n
            \n
            The simplest way is to test if the response from systemd-detect-virt<\/code>\u00a0is \u201cnone.\u201d If it is, the script is running on physical hardware. For all other cases, the script must be running on a virtual machine.<\/div>\n<\/div>\n
            Before we can run the script we must make it executable, using\u00a0chmod<\/code>.<\/p>\n
            chmod +x platform.sh<\/pre>\n
            \"Making<\/p>\n
            It correctly identifies our Ubuntu VirtualBox VM as a virtual machine.<\/p>\n
            .\/platform.sh<\/pre>\n
            \"Using<\/p>\n
            It also correctly detects the GNOME Boxes VM running Fedora.<\/p>\n
            .\/platform.sh<\/pre>\n
            \"Using<\/p>\n
            The script also correctly detects when it is running on a physical machine.<\/p>\n
            .\/platform.sh<\/pre>\n
            \"Using<\/p>\n
            The different\u00a0case<\/code>\u00a0clauses could\u00a0set variables\u00a0that were checked elsewhere in the script to perform different types of processing, or they could call specific functions within your script.<\/p>\n
            If your script needed to detect and accommodate different types of virtual environments, you could add more\u00a0case<\/code>\u00a0clauses, looking for the different strings that\u00a0systemd-detect-virt<\/code>\u00a0can return. We can see the complete list of possible responses by using the\u00a0--list<\/code>\u00a0option. To make it easier to see them all at once, we\u2019ll pipe the output through the\u00a0column<\/code>\u00a0command.<\/p>\n
            systemd-detect-virt --list | column<\/pre>\n
            \"The<\/p>\n","protected":false},"excerpt":{"rendered":"
              Virtual machines\u00a0try really hard to convince their\u00a0operating systems\u00a0that they\u2019re running on physical hardware. So can you tell from\u00a0the Linux command line\u00a0if the computer is physical or virtual? Virtual Machines and Hypervisors A traditional computer is a physical object. It\u2019s a collection of different pieces of hardware that are plugged and bolted together so that […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[1082,1,730,830,42,51,1301,495,501,548,691,1304,107],"tags":[1577,920,1065,1576,14,1580,1579,206,1578,921,421],"class_list":["post-5199","post","type-post","status-publish","format-standard","hentry","category-centos-7-rhel-7","category-viazap","category-clusterweb","category-debian","category-leitura-recomendada","category-linux-linuxrs","category-nuvens","category-profissional-de-ti","category-shell-script","category-ubuntu-2","category-virtualizacao-2","category-vmware-esxi","category-xenserver","tag-detect","tag-how","tag-in","tag-let","tag-linux","tag-machines","tag-running","tag-scripts","tag-theyre","tag-to","tag-virtual"],"_links":{"self":[{"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=\/wp\/v2\/posts\/5199","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=5199"}],"version-history":[{"count":1,"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=\/wp\/v2\/posts\/5199\/revisions"}],"predecessor-version":[{"id":5200,"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=\/wp\/v2\/posts\/5199\/revisions\/5200"}],"wp:attachment":[{"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5199"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5199"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.clusterweb.com.br\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5199"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}