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Who I Think You Are Software engineer, Sysadmin, etc who is... • wanting to learn about namespaces and cgroups • intereseted in containers and how they work • loves turtles (optional) Saturday, September 21, 13

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Modern Linux Server with Containers [email protected] Saturday, September 21, 13

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Overview Saturday, September 21, 13

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Overview • System Designs Saturday, September 21, 13

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Overview • System Designs • Namespaces Saturday, September 21, 13

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Overview • System Designs • Namespaces • Cgroups Saturday, September 21, 13

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Overview • System Designs • Namespaces • Cgroups • Tooling Saturday, September 21, 13

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The Spectrum Saturday, September 21, 13

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Saturday, September 21, 13

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Hypervisor Saturday, September 21, 13

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Container Hypervisor Saturday, September 21, 13

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Container Application Container Hypervisor Saturday, September 21, 13

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WARNING Saturday, September 21, 13

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Saturday, September 21, 13

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Saturday, September 21, 13

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Saturday, September 21, 13

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Saturday, September 21, 13

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Saturday, September 21, 13

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Saturday, September 21, 13

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System Designs Saturday, September 21, 13

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Saturday, September 21, 13

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Hypervisor Saturday, September 21, 13

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Hypervisor • Host provides full hardware environment Saturday, September 21, 13

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Hypervisor • Host provides full hardware environment • Block device, ethernet device, etc Saturday, September 21, 13

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Hypervisor • Host provides full hardware environment • Block device, ethernet device, etc • Guests run a full kernel Saturday, September 21, 13

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Saturday, September 21, 13

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Container Saturday, September 21, 13

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Container • Host provides Kernel Saturday, September 21, 13

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Container • Host provides Kernel • Filesystem, network interface, etc are already there Saturday, September 21, 13

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Container • Host provides Kernel • Filesystem, network interface, etc are already there • Guest starts from /sbin/init Saturday, September 21, 13

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Saturday, September 21, 13

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Application Container Saturday, September 21, 13

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Application Container • Host provides Kernel Saturday, September 21, 13

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Application Container • Host provides Kernel • User data, socket fd, etc are already there Saturday, September 21, 13

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Application Container • Host provides Kernel • User data, socket fd, etc are already there • Starts from application not init Saturday, September 21, 13

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Namespaces Saturday, September 21, 13

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Imagine: cool medieval castle photo *perhaps fog rolling in* Saturday, September 21, 13

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Filesystem Saturday, September 21, 13

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Filesystem • Read-only Saturday, September 21, 13

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Filesystem • Read-only • Shared Saturday, September 21, 13

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Filesystem • Read-only • Shared • Slave Saturday, September 21, 13

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Filesystem • Read-only • Shared • Slave • Private Saturday, September 21, 13

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Read-only Saturday, September 21, 13

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Private bind mount before: after: source/a-file bind/a-file mount -t tmpfs -o size=1M tmpfs source/mnt before: after: source/mnt/tmpfs-file mount -t tmpfs -o size=1M tmpfs bind/mnt2 before: after: bind/mnt2/mnt2-file Saturday, September 21, 13

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Shared bind mount before: after: source/a-file bind/a-file mount -t tmpfs -o size=1M tmpfs source/mnt before: after: source/mnt/tmpfs-file bind/mnt/tmpfs-file mount -t tmpfs -o size=1M tmpfs bind/mnt2 before: after: source/mnt2/mnt2-file bind/mnt2/mnt2-file Saturday, September 21, 13

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Slave bind mount before: after: source/a-file bind/a-file mount -t tmpfs -o size=1M tmpfs source/mnt before: after: source/mnt/tmpfs-file bind/mnt/tmpfs-file mount -t tmpfs -o size=1M tmpfs bind/mnt2 before: after: bind/mnt2/mnt2-file Saturday, September 21, 13

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Patterns • Mounting RO /usr inside a container • Private /tmp per service • Sharing data across containers via binds Saturday, September 21, 13

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Networking Saturday, September 21, 13

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Networking • Root namespace Saturday, September 21, 13

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Networking • Root namespace • Bridging Saturday, September 21, 13

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Networking • Root namespace • Bridging • Private namespace with socket activation Saturday, September 21, 13

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Root Namespace • Full access to the machine interfaces Saturday, September 21, 13

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Root Namespace Saturday, September 21, 13

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Root Namespace • Advantages Saturday, September 21, 13

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Root Namespace • Advantages • Fast Saturday, September 21, 13

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Root Namespace • Advantages • Fast • Easy to get setup Saturday, September 21, 13

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Root Namespace • Advantages • Fast • Easy to get setup • Network looks normal to the container Saturday, September 21, 13

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Root Namespace • Advantages • Fast • Easy to get setup • Network looks normal to the container Saturday, September 21, 13

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Root Namespace • Advantages • Fast • Easy to get setup • Network looks normal to the container • Disadvatages Saturday, September 21, 13

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Root Namespace • Advantages • Fast • Easy to get setup • Network looks normal to the container • Disadvatages • No separation of concerns Saturday, September 21, 13

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Root Namespace • Advantages • Fast • Easy to get setup • Network looks normal to the container • Disadvatages • No separation of concerns • Container has full control Saturday, September 21, 13

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Network Bridges Saturday, September 21, 13

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Network Bridges • Create a bridge, like a virtual switch Saturday, September 21, 13

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Network Bridges • Create a bridge, like a virtual switch • Create container namespace and add interface Saturday, September 21, 13

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Network Bridges • Create a bridge, like a virtual switch • Create container namespace and add interface • Attach container interface to bridge Saturday, September 21, 13

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Network Bridges Saturday, September 21, 13

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Network Bridges • Advantages Saturday, September 21, 13

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Network Bridges • Advantages • More complex to get setup Saturday, September 21, 13

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Network Bridges • Advantages • More complex to get setup • Network looks normal to the container Saturday, September 21, 13

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Network Bridges • Advantages • More complex to get setup • Network looks normal to the container Saturday, September 21, 13

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Network Bridges • Advantages • More complex to get setup • Network looks normal to the container Saturday, September 21, 13

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Network Bridges • Advantages • More complex to get setup • Network looks normal to the container • Disadvantages Saturday, September 21, 13

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Network Bridges • Advantages • More complex to get setup • Network looks normal to the container • Disadvantages • Less speed Saturday, September 21, 13

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Network Bridges • Advantages • More complex to get setup • Network looks normal to the container • Disadvantages • Less speed • NAT to the internet Saturday, September 21, 13

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Network Bridges • Advantages • More complex to get setup • Network looks normal to the container • Disadvantages • Less speed • NAT to the internet • iptables to expose public socket Saturday, September 21, 13

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Socket Activation Saturday, September 21, 13

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Socket Activation • No interface Saturday, September 21, 13

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Socket Activation • No interface • Sockets are passed via stdin (inetd) Saturday, September 21, 13

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Socket Activation • No interface • Sockets are passed via stdin (inetd) • systemd style listen fd API Saturday, September 21, 13

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inetd style Saturday, September 21, 13

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inetd style • Advantages Saturday, September 21, 13

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inetd style • Advantages • Fast and isolated Saturday, September 21, 13

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inetd style • Advantages • Fast and isolated • Simple and well understood Saturday, September 21, 13

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inetd style • Advantages • Fast and isolated • Simple and well understood • Support from existing daemons like ssh Saturday, September 21, 13

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inetd style • Advantages • Fast and isolated • Simple and well understood • Support from existing daemons like ssh • No process running until needed Saturday, September 21, 13

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inetd style • Advantages • Fast and isolated • Simple and well understood • Support from existing daemons like ssh • No process running until needed • Disadvantages Saturday, September 21, 13

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inetd style • Advantages • Fast and isolated • Simple and well understood • Support from existing daemons like ssh • No process running until needed • Disadvantages • One process per client (scaling problems!) Saturday, September 21, 13

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listen fd style Saturday, September 21, 13

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listen fd style • Advantages Saturday, September 21, 13

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listen fd style • Advantages • Fast and isolated Saturday, September 21, 13

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listen fd style • Advantages • Fast and isolated • Only one process needed per service Saturday, September 21, 13

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listen fd style • Advantages • Fast and isolated • Only one process needed per service • No process running until needed Saturday, September 21, 13

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listen fd style • Advantages • Fast and isolated • Only one process needed per service • No process running until needed Saturday, September 21, 13

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listen fd style • Advantages • Fast and isolated • Only one process needed per service • No process running until needed • Disadvantages Saturday, September 21, 13

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listen fd style • Advantages • Fast and isolated • Only one process needed per service • No process running until needed • Disadvantages • Patches required to daemons Saturday, September 21, 13

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Process Namespace • PID 1 is something else outside the namespace Saturday, September 21, 13

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All the Rest Saturday, September 21, 13

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Cgroups Saturday, September 21, 13

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Imagine: an accountant’s overflowing desk perhaps hands on head in dispair Saturday, September 21, 13

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Block I/O • Limit: Weight from 10 to1000 • Limit: Bandwidth limits R/W • Metrics: iops serviced, waiting and queued Saturday, September 21, 13

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CPU • Limit: Shares system 1024 is half of 2048 •Metrics: cpuacct.stats user and system Saturday, September 21, 13

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• Limit: Total RSS memory limit • Metrics: swap, total rss, # page ins/outs Memory Saturday, September 21, 13

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Tooling Saturday, September 21, 13

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docker Saturday, September 21, 13

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nspawn Saturday, September 21, 13

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nsenter Saturday, September 21, 13

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/sys/fs/cgroup Saturday, September 21, 13

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systemd units Saturday, September 21, 13

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systemd-cgtop Saturday, September 21, 13

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Recap Saturday, September 21, 13

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Recap • Containers are built on namespaces and cgroups Saturday, September 21, 13

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Recap • Containers are built on namespaces and cgroups • Namespaces provide isolation similar to hypervisors Saturday, September 21, 13

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Recap • Containers are built on namespaces and cgroups • Namespaces provide isolation similar to hypervisors • Cgroups provide resource limiting and accounting Saturday, September 21, 13

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Recap • Containers are built on namespaces and cgroups • Namespaces provide isolation similar to hypervisors • Cgroups provide resource limiting and accounting • These tools can be mixed to create hybrids Saturday, September 21, 13

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Future Saturday, September 21, 13

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Thanks! @BrandonPhilips @CoreOSLinux Saturday, September 21, 13