Singularity: Difference between revisions

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Containers use Linux <b>control groups</b> (cgroups), kernel <b>namespaces</b>, and an <b>overlay filesystem</b> where:
Containers use Linux <b>control groups</b> (cgroups), kernel <b>namespaces</b>, and an <b>overlay filesystem</b> where:
* cgroups <b>limit, control, and isolate</b> resource usage (e.g., RAM, disk I/O, CPU access)
* cgroups <b>limit, control, and isolate</b> resource usage (e.g., RAM, disk I/O, CPU access),
* kernel namespaces <b>virtualize and isolate</b> operating system resources of a <b>group of processes</b>, e.g., process and user IDs, filesystems, network access; and,
* kernel namespaces <b>virtualize and isolate</b> operating system resources of a <b>group of processes</b>, e.g., process and user IDs, filesystems, network access; and,
* overlay filesystems can be used to enable the <b>appearance</b> of writing to otherwise read-only filesystems.
* overlay filesystems can be used to enable the <b>appearance</b> of writing to otherwise read-only filesystems.
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where <code>WHAT-TO-WRITE</code> is:
where <code>WHAT-TO-WRITE</code> is:
* a filename of the singularity image file (*.sif) where the built image will be written
* a filename of the singularity image file (*.sif) where the built image will be written
* a directory if one is building a <b>sandbox</b> using the <b>--sandbox</b> option typically on one's own (Linux) computer (requiring root account access)
* a directory if one is building a <b>sandbox</b> using the <code>--sandbox</code> option typically on one's own (Linux) computer (requiring root account access)
and <code>SPECIAL-URI-OR-PATH</code> is:
and <code>SPECIAL-URI-OR-PATH</code> is:
* a URI starting with <b>library://</b> to build from a Container Library,
* a URI starting with <b>library://</b> to build from a Container Library,
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For example, Debian and Ubuntu images' <code>dpkg</code>, <code>apt-get</code>, and <code>apt</code> commands all require root to upgrade/install packages. Thus, if the ability to install and upgrade software in the future is important, then create the image on a Linux system where you have root permissions.  
For example, Debian and Ubuntu images <code>dpkg</code>, <code>apt-get</code>, and <code>apt</code> commands all require root to upgrade/install packages. Thus, if the ability to install and upgrade software in the future is important, then create the image on a Linux system where you have root permissions.  


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