% podman-run(1) ## NAME podman\-run - Run a command in a new container ## SYNOPSIS **podman run** [*options*] *image* [*command* [*arg* ...]] ## DESCRIPTION Run a process in a new container. **podman run** starts a process with its own file system, its own networking, and its own isolated process tree. The IMAGE which starts the process may define defaults related to the process that will be run in the container, the networking to expose, and more, but **podman run** gives final control to the operator or administrator who starts the container from the image. For that reason **podman run** has more options than any other podman command. If the IMAGE is not already loaded then **podman run** will pull the IMAGE, and all image dependencies, from the repository in the same way running **podman pull** IMAGE, before it starts the container from that image. Several files will be automatically created within the container. These include `/etc/hosts`, `/etc/hostname`, and `/etc/resolv.conf` to manage networking. These will be based on the host's version of the files, though they can be customized with options (for example, **--dns** will override the host's DNS servers in the created `resolv.conf`). Additionally, an empty file is created in each container to indicate to programs they are running in a container. This file is located at `/run/.containerenv`. ## OPTIONS **--add-host**=[] Add a custom host-to-IP mapping (host:ip) Add a line to /etc/hosts. The format is hostname:ip. The **--add-host** option can be set multiple times. **--annotation**=[] Add an annotation to the container. The format is key=value. The **--annotation** option can be set multiple times. **-a**, **--attach**=[] Attach to STDIN, STDOUT or STDERR. In foreground mode (the default when **-d** is not specified), **podman run** can start the process in the container and attach the console to the process's standard input, output, and standard error. It can even pretend to be a TTY (this is what most commandline executables expect) and pass along signals. The **-a** option can be set for each of stdin, stdout, and stderr. **--blkio-weight**=*0* Block IO weight (relative weight) accepts a weight value between 10 and 1000. **--blkio-weight-device**=[] Block IO weight (relative device weight, format: `DEVICE_NAME:WEIGHT`). **--cap-add**=[] Add Linux capabilities **--cap-drop**=[] Drop Linux capabilities **--cgroup-parent**="" Path to cgroups under which the cgroup for the container will be created. If the path is not absolute, the path is considered to be relative to the cgroups path of the init process. Cgroups will be created if they do not already exist. **--cidfile**="" Write the container ID to the file **--conmon-pidfile**="" Write the pid of the `conmon` process to a file. `conmon` daemonizes separate from Podman, so this is necessary when using systemd to restart Podman containers. **--cpu-period**=*0* Limit the CPU CFS (Completely Fair Scheduler) period Limit the container's CPU usage. This flag tell the kernel to restrict the container's CPU usage to the period you specify. **--cpu-quota**=*0* Limit the CPU CFS (Completely Fair Scheduler) quota Limit the container's CPU usage. By default, containers run with the full CPU resource. This flag tell the kernel to restrict the container's CPU usage to the quota you specify. **--cpu-rt-period**=0 Limit the CPU real-time period in microseconds Limit the container's Real Time CPU usage. This flag tell the kernel to restrict the container's Real Time CPU usage to the period you specify. **--cpu-rt-runtime**=0 Limit the CPU real-time runtime in microseconds Limit the containers Real Time CPU usage. This flag tells the kernel to limit the amount of time in a given CPU period Real Time tasks may consume. Ex: Period of 1,000,000us and Runtime of 950,000us means that this container could consume 95% of available CPU and leave the remaining 5% to normal priority tasks. The sum of all runtimes across containers cannot exceed the amount allotted to the parent cgroup. **--cpu-shares**=*0* CPU shares (relative weight) By default, all containers get the same proportion of CPU cycles. This proportion can be modified by changing the container's CPU share weighting relative to the weighting of all other running containers. To modify the proportion from the default of 1024, use the **--cpu-shares** flag to set the weighting to 2 or higher. The proportion will only apply when CPU-intensive processes are running. When tasks in one container are idle, other containers can use the left-over CPU time. The actual amount of CPU time will vary depending on the number of containers running on the system. For example, consider three containers, one has a cpu-share of 1024 and two others have a cpu-share setting of 512. When processes in all three containers attempt to use 100% of CPU, the first container would receive 50% of the total CPU time. If you add a fourth container with a cpu-share of 1024, the first container only gets 33% of the CPU. The remaining containers receive 16.5%, 16.5% and 33% of the CPU. On a multi-core system, the shares of CPU time are distributed over all CPU cores. Even if a container is limited to less than 100% of CPU time, it can use 100% of each individual CPU core. For example, consider a system with more than three cores. If you start one container **{C0}** with **-c=512** running one process, and another container **{C1}** with **-c=1024** running two processes, this can result in the following division of CPU shares: PID container CPU CPU share 100 {C0} 0 100% of CPU0 101 {C1} 1 100% of CPU1 102 {C1} 2 100% of CPU2 **--cpus**=0.0 Number of CPUs. The default is *0.0* which means no limit. **--cpuset-cpus**="" CPUs in which to allow execution (0-3, 0,1) **--cpuset-mems**="" Memory nodes (MEMs) in which to allow execution (0-3, 0,1). Only effective on NUMA systems. If you have four memory nodes on your system (0-3), use `--cpuset-mems=0,1` then processes in your container will only use memory from the first two memory nodes. **-d**, **--detach**=*true*|*false* Detached mode: run the container in the background and print the new container ID. The default is *false*. At any time you can run **podman ps** in the other shell to view a list of the running containers. You can reattach to a detached container with **podman attach**. If you choose to run a container in the detached mode, then you cannot use the **-rm** option. When attached in the tty mode, you can detach from the container (and leave it running) using a configurable key sequence. The default sequence is `CTRL-p CTRL-q`. You configure the key sequence using the **--detach-keys** option or a configuration file. See **config-json(5)** for documentation on using a configuration file. **--detach-keys**="" Override the key sequence for detaching a container. Format is a single character `[a-Z]` or `ctrl-` where `` is one of: `a-z`, `@`, `^`, `[`, `,` or `_`. **--device**=[] Add a host device to the container (e.g. --device=/dev/sdc:/dev/xvdc:rwm) **--device-read-bps**=[] Limit read rate (bytes per second) from a device (e.g. --device-read-bps=/dev/sda:1mb) **--device-read-iops**=[] Limit read rate (IO per second) from a device (e.g. --device-read-iops=/dev/sda:1000) **--device-write-bps**=[] Limit write rate (bytes per second) to a device (e.g. --device-write-bps=/dev/sda:1mb) **--device-write-iops**=[] Limit write rate (IO per second) to a device (e.g. --device-write-iops=/dev/sda:1000) **--dns**=[] Set custom DNS servers This option can be used to override the DNS configuration passed to the container. Typically this is necessary when the host DNS configuration is invalid for the container (e.g., 127.0.0.1). When this is the case the **--dns** flags is necessary for every run. **--dns-option**=[] Set custom DNS options **--dns-search**=[] Set custom DNS search domains (Use --dns-search=. if you don't wish to set the search domain) **--entrypoint** *"command"* | *'["command", "arg1", ...]'* Overwrite the default ENTRYPOINT of the image This option allows you to overwrite the default entrypoint of the image. The ENTRYPOINT of an image is similar to a COMMAND because it specifies what executable to run when the container starts, but it is (purposely) more difficult to override. The ENTRYPOINT gives a container its default nature or behavior, so that when you set an ENTRYPOINT you can run the container as if it were that binary, complete with default options, and you can pass in more options via the COMMAND. But, sometimes an operator may want to run something else inside the container, so you can override the default ENTRYPOINT at runtime by using a **--entrypoint** and a string to specify the new ENTRYPOINT. You need to specify multi option commands in the form of a json string. **-e**, **--env**=[] Set environment variables This option allows you to specify arbitrary environment variables that are available for the process that will be launched inside of the container. **--env-file**=[] Read in a line delimited file of environment variables **--expose**=[] Expose a port, or a range of ports (e.g. --expose=3300-3310) to set up port redirection on the host system. **--gidmap**=container_gid:host_gid:amount **--gidmap**=0:30000:2000 Run the container in a new user namespace using the supplied mapping. This option conflicts with the --userns and --subgidname flags. This option can be passed several times to map different ranges. If calling podman run as an unprivileged user, the user needs to have the right to use the mapping. See `subuid(5)`. The example maps gids 0-2000 in the container to the gids 30000-31999 on the host. **--group-add**=[] Add additional groups to run as **--hostname**="" Container host name Sets the container host name that is available inside the container. **--help** Print usage statement **--image-volume**, **builtin-volume**=*bind*|*tmpfs*|*ignore* Tells podman how to handle the builtin image volumes. The options are: `bind`, `tmpfs`, or `ignore` (default `bind`) - `bind`: A directory is created inside the container state directory and bind mounted into the container for the volumes. - `tmpfs`: The volume is mounted onto the container as a tmpfs, which allows the users to create content that disappears when the container is stopped. - `ignore`: All volumes are just ignored and no action is taken. **-i**, **--interactive**=*true*|*false* Keep STDIN open even if not attached. The default is *false*. When set to true, keep stdin open even if not attached. The default is false. **--ip6**="" Not implemented **--ip**="" Not implemented **--ipc**="" Default is to create a private IPC namespace (POSIX SysV IPC) for the container - `container:`: reuses another container shared memory, semaphores and message queues - `host`: use the host shared memory,semaphores and message queues inside the container. Note: the host mode gives the container full access to local shared memory and is therefore considered insecure. - `ns:` path to an IPC namespace to join. **--kernel-memory**="" Kernel memory limit (format: `[]`, where unit = b, k, m or g) Constrains the kernel memory available to a container. If a limit of 0 is specified (not using `--kernel-memory`), the container's kernel memory is not limited. If you specify a limit, it may be rounded up to a multiple of the operating system's page size and the value can be very large, millions of trillions. **-l**, **--label**=[] Add metadata to a container (e.g., --label com.example.key=value) **--label-file**=[] Read in a line delimited file of labels **--link-local-ip**=[] Not implemented **--log-driver**="*json-file*" Logging driver for the container. Default is defined by daemon `--log-driver` flag. **Warning**: the `podman logs` command works only for the `json-file` and `journald` logging drivers. **--log-opt**=[] Logging driver specific options. `path=/var/log/container/mycontainer.json`: Set the path to the container log file. **--mac-address**="" Container MAC address (e.g. `92:d0:c6:0a:29:33`) Remember that the MAC address in an Ethernet network must be unique. The IPv6 link-local address will be based on the device's MAC address according to RFC4862. Not currently supported **-m**, **--memory**="" Memory limit (format: [], where unit = b, k, m or g) Allows you to constrain the memory available to a container. If the host supports swap memory, then the **-m** memory setting can be larger than physical RAM. If a limit of 0 is specified (not using **-m**), the container's memory is not limited. The actual limit may be rounded up to a multiple of the operating system's page size (the value would be very large, that's millions of trillions). **--memory-reservation**="" Memory soft limit (format: [], where unit = b, k, m or g) After setting memory reservation, when the system detects memory contention or low memory, containers are forced to restrict their consumption to their reservation. So you should always set the value below **--memory**, otherwise the hard limit will take precedence. By default, memory reservation will be the same as memory limit. **--memory-swap**="LIMIT" A limit value equal to memory plus swap. Must be used with the **-m** (**--memory**) flag. The swap `LIMIT` should always be larger than **-m** (**--memory**) value. By default, the swap `LIMIT` will be set to double the value of --memory. The format of `LIMIT` is `[]`. Unit can be `b` (bytes), `k` (kilobytes), `m` (megabytes), or `g` (gigabytes). If you don't specify a unit, `b` is used. Set LIMIT to `-1` to enable unlimited swap. **--memory-swappiness**="" Tune a container's memory swappiness behavior. Accepts an integer between 0 and 100. **--name**="" Assign a name to the container The operator can identify a container in three ways: - UUID long identifier (“f78375b1c487e03c9438c729345e54db9d20cfa2ac1fc3494b6eb60872e74778”) - UUID short identifier (“f78375b1c487”) - Name (“jonah”) podman generates a UUID for each container, and if a name is not assigned to the container with **--name** then the daemon will also generate a random string name. The name is useful any place you need to identify a container. This works for both background and foreground containers. **--network**="*bridge*" Set the Network mode for the container: - `bridge`: create a network stack on the default bridge - `none`: no networking - `container:`: reuse another container's network stack - `host`: use the podman host network stack. Note: the host mode gives the container full access to local system services such as D-bus and is therefore considered insecure. - `|`: connect to a user-defined network - `ns:` path to a network namespace to join **--network-alias**=[] Not implemented **--oom-kill-disable**=*true*|*false* Whether to disable OOM Killer for the container or not. **--oom-score-adj**="" Tune the host's OOM preferences for containers (accepts -1000 to 1000) **--pid**="" Set the PID mode for the container Default is to create a private PID namespace for the container - `container:`: join another container's PID namespace - `host`: use the host's PID namespace for the container. Note: the host mode gives the container full access to local PID and is therefore considered insecure. - `ns`: join the specified PID namespace **--pids-limit**="" Tune the container's pids limit. Set `-1` to have unlimited pids for the container. **--pod**="" Run container in an existing pod **--privileged**=*true*|*false* Give extended privileges to this container. The default is *false*. By default, podman containers are “unprivileged” (=false) and cannot, for example, modify parts of the kernel. This is because by default a container is not allowed to access any devices. A “privileged” container is given access to all devices. When the operator executes **podman run --privileged**, podman enables access to all devices on the host as well as set turn off most of the security measures protecting the host from the container. **-p**, **--publish**=[] Publish a container's port, or range of ports, to the host Format: `ip:hostPort:containerPort | ip::containerPort | hostPort:containerPort | containerPort` Both hostPort and containerPort can be specified as a range of ports. When specifying ranges for both, the number of container ports in the range must match the number of host ports in the range. (e.g., `podman run -p 1234-1236:1222-1224 --name thisWorks -t busybox` but not `podman run -p 1230-1236:1230-1240 --name RangeContainerPortsBiggerThanRangeHostPorts -t busybox`) With ip: `podman run -p 127.0.0.1:$HOSTPORT:$CONTAINERPORT --name CONTAINER -t someimage` Use `podman port` to see the actual mapping: `podman port CONTAINER $CONTAINERPORT` **-P**, **--publish-all**=*true*|*false* Publish all exposed ports to random ports on the host interfaces. The default is *false*. When set to true publish all exposed ports to the host interfaces. The default is false. If the operator uses -P (or -p) then podman will make the exposed port accessible on the host and the ports will be available to any client that can reach the host. When using -P, podman will bind any exposed port to a random port on the host within an *ephemeral port range* defined by `/proc/sys/net/ipv4/ip_local_port_range`. To find the mapping between the host ports and the exposed ports, use `podman port`. **--quiet, -q** Suppress output information when pulling images **--read-only**=*true*|*false* Mount the container's root filesystem as read only. By default a container will have its root filesystem writable allowing processes to write files anywhere. By specifying the `--read-only` flag the container will have its root filesystem mounted as read only prohibiting any writes. **--rm**=*true*|*false* Automatically remove the container when it exits. The default is *false*. Note that the container will not be removed when it could not be created or started successfully. This allows the user to inspect the container after failure. The `--rm` flag is incompatible with the `-d` flag. **--rootfs** If specified, the first argument refers to an exploded container on the file system. This is useful to run a container without requiring any image management, the rootfs of the container is assumed to be managed externally. **--security-opt**=[] Security Options - `apparmor=unconfined` : Turn off apparmor confinement for the container - `apparmor=your-profile` : Set the apparmor confinement profile for the container - `label=user:USER` : Set the label user for the container - `label=role:ROLE` : Set the label role for the container - `label=type:TYPE` : Set the label type for the container - `label=level:LEVEL` : Set the label level for the container - `label=disable` : Turn off label confinement for the container - `no-new-privileges` : Disable container processes from gaining additional privileges - `seccomp=unconfined` : Turn off seccomp confinement for the container - `seccomp=profile.json` : White listed syscalls seccomp Json file to be used as a seccomp filter **--shm-size**="" Size of `/dev/shm`. The format is ``. `number` must be greater than `0`. Unit is optional and can be `b` (bytes), `k` (kilobytes), `m`(megabytes), or `g` (gigabytes). If you omit the unit, the system uses bytes. If you omit the size entirely, the system uses `64m`. **--sig-proxy**=*true*|*false* Proxy signals sent to the `podman run` command to the container process. SIGCHLD, SIGSTOP, and SIGKILL are not proxied. The default is *true*. **--stop-signal**=*SIGTERM* Signal to stop a container. Default is SIGTERM. **--stop-timeout**=*10* Timeout (in seconds) to stop a container. Default is 10. **--subgidname**=name Run the container in a new user namespace using the map with 'name' in the `/etc/subgid` file. If calling podman run as an unprivileged user, the user needs to have the right to use the mapping. See `subgid(5)`. This flag conflicts with `--userns` and `--gidmap`. **--subuidname**=name Run the container in a new user namespace using the map with 'name' in the `/etc/subuid` file. If calling podman run as an unprivileged user, the user needs to have the right to use the mapping. See `subuid(5)`. This flag conflicts with `--userns` and `--uidmap`. **--sysctl**=SYSCTL Configure namespaced kernel parameters at runtime IPC Namespace - current sysctls allowed: - kernel.msgmax - kernel.msgmnb - kernel.msgmni - kernel.sem - kernel.shmall - kernel.shmmax - kernel.shmmni - kernel.shm_rmid_forced - Sysctls beginning with fs.mqueue.* Note: if you use the `--ipc=host` option these sysctls will not be allowed. Network Namespace - current sysctls allowed: - Sysctls beginning with net.* Note: if you use the `--network=host` option these sysctls will not be allowed. **--systemd**=*true*|*false* Run container in systemd mode. The default is *true*. If the command you running inside of the container is systemd or init, podman will setup tmpfs mount points in the following directories: /run, /run/lock, /tmp, /sys/fs/cgroup/systemd, /var/lib/journal It will also set the default stop signal to SIGRTMIN+3. This allow systemd to run in a confined container without any modifications. **--tmpfs**=[] Create a tmpfs mount Mount a temporary filesystem (`tmpfs`) mount into a container, for example: $ podman run -d --tmpfs /tmp:rw,size=787448k,mode=1777 my_image This command mounts a `tmpfs` at `/tmp` within the container. The supported mount options are the same as the Linux default `mount` flags. If you do not specify any options, the systems uses the following options: `rw,noexec,nosuid,nodev,size=65536k`. **-t**, **--tty**=*true*|*false* Allocate a pseudo-TTY. The default is *false*. When set to true podman will allocate a pseudo-tty and attach to the standard input of the container. This can be used, for example, to run a throwaway interactive shell. The default is false. **NOTE**: The **-t** option is incompatible with a redirection of the podman client standard input. **--uidmap**=container_uid:host_uid:amount **--uidmap**=0:30000:2000 Run the container in a new user namespace using the supplied mapping. This option conflicts with the --userns and --subuidname flags. This option can be passed several times to map different ranges. If calling podman run as an unprivileged user, the user needs to have the right to use the mapping. See `subuid(5)`. The example maps uids 0-2000 in the container to the uids 30000-31999 on the host. **--ulimit**=[] Ulimit options **-u**, **--user**="" Sets the username or UID used and optionally the groupname or GID for the specified command. The followings examples are all valid: --user [user | user:group | uid | uid:gid | user:gid | uid:group ] Without this argument the command will be run as root in the container. **--userns**=host **--userns**=ns:my_namespace Set the user namespace for the container. - `host`: run in the user namespace of the caller. This is the default if no user namespace options are set. The processes running in the container will have the same privileges on the host as any other process launched by the calling user. - `ns`: run the container in the given existing user namespace. This option is incompatible with --gidmap, --uidmap, --subuid and --subgid **--uts**=*host* Set the UTS mode for the container `host`: use the host's UTS namespace inside the container. `ns`: specify the usernamespace to use. **NOTE**: the host mode gives the container access to changing the host's hostname and is therefore considered insecure. **-v**|**--volume**[=*[HOST-DIR:CONTAINER-DIR[:OPTIONS]]*] Create a bind mount. If you specify, ` -v /HOST-DIR:/CONTAINER-DIR`, podman bind mounts `/HOST-DIR` in the host to `/CONTAINER-DIR` in the podman container. The `OPTIONS` are a comma delimited list and can be: * [`rw`|`ro`] * [`z`|`Z`] * [`[r]shared`|`[r]slave`|`[r]private`] The `CONTAINER-DIR` must be an absolute path such as `/src/docs`. The `HOST-DIR` must be an absolute path as well. podman bind-mounts the `HOST-DIR` to the path you specify. For example, if you supply the `/foo` value, podman creates a bind-mount. You can specify multiple **-v** options to mount one or more mounts to a container. You can add `:ro` or `:rw` suffix to a volume to mount it read-only or read-write mode, respectively. By default, the volumes are mounted read-write. See examples. Labeling systems like SELinux require that proper labels are placed on volume content mounted into a container. Without a label, the security system might prevent the processes running inside the container from using the content. By default, podman does not change the labels set by the OS. To change a label in the container context, you can add either of two suffixes `:z` or `:Z` to the volume mount. These suffixes tell podman to relabel file objects on the shared volumes. The `z` option tells podman that two containers share the volume content. As a result, podman labels the content with a shared content label. Shared volume labels allow all containers to read/write content. The `Z` option tells podman to label the content with a private unshared label. Only the current container can use a private volume. By default bind mounted volumes are `private`. That means any mounts done inside container will not be visible on host and vice versa. One can change this behavior by specifying a volume mount propagation property. Making a volume `shared` mounts done under that volume inside container will be visible on host and vice versa. Making a volume `slave` enables only one way mount propagation and that is mounts done on host under that volume will be visible inside container but not the other way around. To control mount propagation property of volume one can use `:[r]shared`, `:[r]slave` or `:[r]private` propagation flag. Propagation property can be specified only for bind mounted volumes and not for internal volumes or named volumes. For mount propagation to work source mount point (mount point where source dir is mounted on) has to have right propagation properties. For shared volumes, source mount point has to be shared. And for slave volumes, source mount has to be either shared or slave. Use `df ` to figure out the source mount and then use `findmnt -o TARGET,PROPAGATION ` to figure out propagation properties of source mount. If `findmnt` utility is not available, then one can look at mount entry for source mount point in `/proc/self/mountinfo`. Look at `optional fields` and see if any propagation properties are specified. `shared:X` means mount is `shared`, `master:X` means mount is `slave` and if nothing is there that means mount is `private`. To change propagation properties of a mount point use `mount` command. For example, if one wants to bind mount source directory `/foo` one can do `mount --bind /foo /foo` and `mount --make-private --make-shared /foo`. This will convert /foo into a `shared` mount point. Alternatively one can directly change propagation properties of source mount. Say `/` is source mount for `/foo`, then use `mount --make-shared /` to convert `/` into a `shared` mount. **--volumes-from**[=*CONTAINER*[:*OPTIONS*]] Mount volumes from the specified container(s). *OPTIONS* is a comma delimited list with the following available elements: * [rw|ro] * z Mounts already mounted volumes from a source container onto another container. You must supply the source's container-id or container-name. To share a volume, use the --volumes-from option when running the target container. You can share volumes even if the source container is not running. By default, podman mounts the volumes in the same mode (read-write or read-only) as it is mounted in the source container. Optionally, you can change this by suffixing the container-id with either the `ro` or `rw` keyword. Labeling systems like SELinux require that proper labels are placed on volume content mounted into a container. Without a label, the security system might prevent the processes running inside the container from using the content. By default, podman does not change the labels set by the OS. To change a label in the container context, you can add `z` to the volume mount. This suffix tells podman to relabel file objects on the shared volumes. The `z` option tells podman that two containers share the volume content. As a result, podman labels the content with a shared content label. Shared volume labels allow all containers to read/write content. If the location of the volume from the source container overlaps with data residing on a target container, then the volume hides that data on the target. **-w**, **--workdir**="" Working directory inside the container The default working directory for running binaries within a container is the root directory (/). The image developer can set a different default with the WORKDIR instruction. The operator can override the working directory by using the **-w** option. ## Exit Status The exit code from `podman run` gives information about why the container failed to run or why it exited. When `podman run` exits with a non-zero code, the exit codes follow the `chroot` standard, see below: **_125_** if the error is with podman **_itself_** $ podman run --foo busybox; echo $? # flag provided but not defined: --foo See 'podman run --help'. 125 **_126_** if the **_contained command_** cannot be invoked $ podman run busybox /etc; echo $? # exec: "/etc": permission denied podman: Error response from daemon: Contained command could not be invoked 126 **_127_** if the **_contained command_** cannot be found $ podman run busybox foo; echo $? # exec: "foo": executable file not found in $PATH podman: Error response from daemon: Contained command not found or does not exist 127 **_Exit code_** of **_contained command_** otherwise $ podman run busybox /bin/sh -c 'exit 3' # 3 ## EXAMPLES ### Running container in read-only mode During container image development, containers often need to write to the image content. Installing packages into /usr, for example. In production, applications seldom need to write to the image. Container applications write to volumes if they need to write to file systems at all. Applications can be made more secure by running them in read-only mode using the - -read-only switch. This protects the containers image from modification. Read only containers may still need to write temporary data. The best way to handle this is to mount tmpfs directories on /run and /tmp. ``` $ podman run --read-only --tmpfs /run --tmpfs /tmp -i -t fedora /bin/bash ``` ### Exposing log messages from the container to the host's log If you want messages that are logged in your container to show up in the host's syslog/journal then you should bind mount the /dev/log directory as follows. ``` $ podman run -v /dev/log:/dev/log -i -t fedora /bin/bash ``` From inside the container you can test this by sending a message to the log. ``` (bash)# logger "Hello from my container" ``` Then exit and check the journal. ``` (bash)# exit $ journalctl -b | grep Hello ``` This should list the message sent to logger. ### Attaching to one or more from STDIN, STDOUT, STDERR If you do not specify -a then podman will attach everything (stdin,stdout,stderr). You can specify to which of the three standard streams (stdin, stdout, stderr) you'd like to connect instead, as in: ``` $ podman run -a stdin -a stdout -i -t fedora /bin/bash ``` ## Sharing IPC between containers Using shm_server.c available here: https://www.cs.cf.ac.uk/Dave/C/node27.html Testing `--ipc=host` mode: Host shows a shared memory segment with 7 pids attached, happens to be from httpd: ``` $ sudo ipcs -m ------ Shared Memory Segments -------- key shmid owner perms bytes nattch status 0x01128e25 0 root 600 1000 7 ``` Now run a regular container, and it correctly does NOT see the shared memory segment from the host: ``` $ podman run -it shm ipcs -m ------ Shared Memory Segments -------- key shmid owner perms bytes nattch status ``` Run a container with the new `--ipc=host` option, and it now sees the shared memory segment from the host httpd: ``` $ podman run -it --ipc=host shm ipcs -m ------ Shared Memory Segments -------- key shmid owner perms bytes nattch status 0x01128e25 0 root 600 1000 7 ``` Testing `--ipc=container:CONTAINERID` mode: Start a container with a program to create a shared memory segment: ``` $ podman run -it shm bash $ sudo shm/shm_server & $ sudo ipcs -m ------ Shared Memory Segments -------- key shmid owner perms bytes nattch status 0x0000162e 0 root 666 27 1 ``` Create a 2nd container correctly shows no shared memory segment from 1st container: ``` $ podman run shm ipcs -m ------ Shared Memory Segments -------- key shmid owner perms bytes nattch status ``` Create a 3rd container using the new --ipc=container:CONTAINERID option, now it shows the shared memory segment from the first: ``` $ podman run -it --ipc=container:ed735b2264ac shm ipcs -m $ sudo ipcs -m ------ Shared Memory Segments -------- key shmid owner perms bytes nattch status 0x0000162e 0 root 666 27 1 ``` ### Mapping Ports for External Usage The exposed port of an application can be mapped to a host port using the **-p** flag. For example, an httpd port 80 can be mapped to the host port 8080 using the following: ``` $ podman run -p 8080:80 -d -i -t fedora/httpd ``` ### Mounting External Volumes To mount a host directory as a container volume, specify the absolute path to the directory and the absolute path for the container directory separated by a colon: ``` $ podman run -v /var/db:/data1 -i -t fedora bash ``` When using SELinux, be aware that the host has no knowledge of container SELinux policy. Therefore, in the above example, if SELinux policy is enforced, the `/var/db` directory is not writable to the container. A "Permission Denied" message will occur and an avc: message in the host's syslog. To work around this, at time of writing this man page, the following command needs to be run in order for the proper SELinux policy type label to be attached to the host directory: ``` $ chcon -Rt svirt_sandbox_file_t /var/db ``` Now, writing to the /data1 volume in the container will be allowed and the changes will also be reflected on the host in /var/db. ### Using alternative security labeling You can override the default labeling scheme for each container by specifying the `--security-opt` flag. For example, you can specify the MCS/MLS level, a requirement for MLS systems. Specifying the level in the following command allows you to share the same content between containers. ``` podman run --security-opt label=level:s0:c100,c200 -i -t fedora bash ``` An MLS example might be: ``` $ podman run --security-opt label=level:TopSecret -i -t rhel7 bash ``` To disable the security labeling for this container versus running with the `--permissive` flag, use the following command: ``` $ podman run --security-opt label=disable -i -t fedora bash ``` If you want a tighter security policy on the processes within a container, you can specify an alternate type for the container. You could run a container that is only allowed to listen on Apache ports by executing the following command: ``` $ podman run --security-opt label=type:svirt_apache_t -i -t centos bash ``` Note: You would have to write policy defining a `svirt_apache_t` type. ### Setting device weight If you want to set `/dev/sda` device weight to `200`, you can specify the device weight by `--blkio-weight-device` flag. Use the following command: ``` $ podman run -it --blkio-weight-device "/dev/sda:200" ubuntu ``` ### Setting Namespaced Kernel Parameters (Sysctls) The `--sysctl` sets namespaced kernel parameters (sysctls) in the container. For example, to turn on IP forwarding in the containers network namespace, run this command: ``` $ podman run --sysctl net.ipv4.ip_forward=1 someimage ``` Note: Not all sysctls are namespaced. podman does not support changing sysctls inside of a container that also modify the host system. As the kernel evolves we expect to see more sysctls become namespaced. See the definition of the `--sysctl` option above for the current list of supported sysctls. ### Set UID/GID mapping in a new user namespace If you want to run the container in a new user namespace and define the mapping of the uid and gid from the host. ``` $ podman run --uidmap 0:30000:7000 --gidmap 0:30000:7000 fedora echo hello ``` ## FILES **/etc/subuid** **/etc/subgid** ## SEE ALSO subgid(5), subuid(5) ## HISTORY October 2017, converted from Docker documentation to podman by Dan Walsh for podman November 2015, updated by Sally O'Malley July 2014, updated by Sven Dowideit June 2014, updated by Sven Dowideit April 2014, Originally compiled by William Henry based on docker.com source material and internal work.