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<!--replace-end-7--><!--replace-end-4--><!--replace-end-1--></head><body><div class="ui fluid container universe"><!--replace-start-2--><!--replace-start-3--><!--replace-start-6--><div class="ui text container" id="zettel-container" style="position: relative"><div class="zettel-view"><article class="ui raised attached segment zettel-content"><div class="pandoc"><h1 id="title-h1">User space</h1><p>User space is the portion of the main memory that the kernel allocates for user processes.</p><p>There is a hierarchy within the user space with several different groups of user processes:</p><dl>
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<dt>Basic services</dt>
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<dd>Run at the bottom level and therefore are closest to ther kernel. Comprises small components that perform single, uncomplicated tasks. Examples include network configuration, the communication bus, and diagnostic logging</dd>
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<dt>Utiility services</dt>
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<dd>The middle level: larger components such as mail, print, and database services</dd>
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<dt>Services controllable by the user</dt>
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<dd>The top level: complicated tasks that the user controls directly such as using a web-browser, editing a text file</dd>
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</dl>
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<h2 id="what-is-a-user">What is a user?</h2><blockquote><p>A user is an entity that can run processes and own files.</p></blockquote><p>At the level of users, a user is associated with a user name however the kernel does not manage usernames, it identifies users via numeric identifiers called <strong>user IDs</strong>.</p><p>Users exist in order to support permissions and access boundaries. A user may terminate or modify the behaviour of its own processes (within limits) but cannot interfere with another user’s proceses. In addition, users may own files and choose whether to share them with other users.</p><h3 id="root-user-superuser">Root user (superuser)</h3><p>A Linux system normally has a number of users in addition to the ones that correspond to the real human users. The most important is <strong>root</strong>. The root user <em>can</em> terminate and alter another user’s processes and access any file on the local system.</p><p>A person who can operate as root is an administrator on a typical user system.</p></div></article><nav class="ui attached segment deemphasized backlinksPane" id="neuron-backlinks-pane"><h3 class="ui header">Backlinks</h3><ul class="backlinks"><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="What_are_disks.html">What are disks?</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc">The <strong>filesystem</strong> is a database of files and directories: this comprises the bulk of the partition and is what you interact with in <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: User space"><a href="User_Space.html">user space</a></span></span> when reading and writing data.</div></li></ul></li><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="Threads.html">Threads</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc"><p>Both procesess in <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: User space"><a href="User_Space.html">user space</a></span></span> and the <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: The kernel"><a href="The_kernel.html">kernel</a></span></span> utilise threads.</p></div></li></ul></li><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="Containerization.html">Containerizaton</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc"><p>In ordinary <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: User space"><a href="User_Space.html">user space</a></span></span> applications share the <em>same</em> processor, memory and file system resources. This increases the likelihood of resourcing challenges, dependency conflicts and security threats. Without modularisation and the titration of resources, you are opened up to much greater possibility of failure.</p></div></li></ul></li><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="Boot_process.html">The boot process</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc">The kernel starts a program called <strong>init</strong>. It has a <a href="Processes.md#processes-ps">process id</a> of 1. This is the point at which <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: User space"><a href="User_Space.html">user space</a></span></span> starts.</div></li></ul></li></ul></nav><nav class="ui attached segment deemphasized bottomPane" id="neuron-tags-pane"><div><span class="ui basic label zettel-tag" title="Tag">operating-systems</span></div></nav><nav class="ui bottom attached icon compact inverted menu blue" id="neuron-nav-bar"><!--replace-start-9--><!--replace-end-9--><a class="right item" href="impulse.html" title="Open Impulse"><i class="wave square icon"></i></a></nav></div></div><!--replace-end-6--><!--replace-end-3--><!--replace-end-2--><div class="ui center aligned container footer-version"><div class="ui tiny image"><a href="https://neuron.zettel.page"><img alt="logo" src="https://raw.githubusercontent.com/srid/neuron/master/assets/neuron.svg" title="Generated by Neuron 1.9.35.3" /></a></div></div></div></body></html> |