github.com/thajeztah/cli@v0.0.0-20240223162942-dc6bfac81a8b/docs/reference/run.md (about) 1 --- 2 description: "Running and configuring containers with the Docker CLI" 3 keywords: "docker, run, cli" 4 aliases: 5 - /reference/run/ 6 title: Running containers 7 --- 8 9 Docker runs processes in isolated containers. A container is a process 10 which runs on a host. The host may be local or remote. When an you 11 execute `docker run`, the container process that runs is isolated in 12 that it has its own file system, its own networking, and its own 13 isolated process tree separate from the host. 14 15 This page details how to use the `docker run` command to run containers. 16 17 ## General form 18 19 A `docker run` command takes the following form: 20 21 ```console 22 $ docker run [OPTIONS] IMAGE[:TAG|@DIGEST] [COMMAND] [ARG...] 23 ``` 24 25 The `docker run` command must specify an [image reference](#image-references) 26 to create the container from. 27 28 ### Image references 29 30 The image reference is the name and version of the image. You can use the image 31 reference to create or run a container based on an image. 32 33 - `docker run IMAGE[:TAG][@DIGEST]` 34 - `docker create IMAGE[:TAG][@DIGEST]` 35 36 An image tag is the image version, which defaults to `latest` when omitted. Use 37 the tag to run a container from specific version of an image. For example, to 38 run version `23.10` of the `ubuntu` image: `docker run ubuntu:23.10`. 39 40 #### Image digests 41 42 Images using the v2 or later image format have a content-addressable identifier 43 called a digest. As long as the input used to generate the image is unchanged, 44 the digest value is predictable. 45 46 The following example runs a container from the `alpine` image with the 47 `sha256:9cacb71397b640eca97488cf08582ae4e4068513101088e9f96c9814bfda95e0` digest: 48 49 ```console 50 $ docker run alpine@sha256:9cacb71397b640eca97488cf08582ae4e4068513101088e9f96c9814bfda95e0 date 51 ``` 52 53 ### Options 54 55 `[OPTIONS]` let you configure options for the container. For example, you can 56 give the container a name (`--name`), or run it as a background process (`-d`). 57 You can also set options to control things like resource constraints and 58 networking. 59 60 ### Commands and arguments 61 62 You can use the `[COMMAND]` and `[ARG...]` positional arguments to specify 63 commands and arguments for the container to run when it starts up. For example, 64 you can specify `sh` as the `[COMMAND]`, combined with the `-i` and `-t` flags, 65 to start an interactive shell in the container (if the image you select has an 66 `sh` executable on `PATH`). 67 68 ```console 69 $ docker run -it IMAGE sh 70 ``` 71 72 > **Note** 73 > 74 > Depending on your Docker system configuration, you may be 75 > required to preface the `docker run` command with `sudo`. To avoid 76 > having to use `sudo` with the `docker` command, your system 77 > administrator can create a Unix group called `docker` and add users to 78 > it. For more information about this configuration, refer to the Docker 79 > installation documentation for your operating system. 80 81 ## Foreground and background 82 83 When you start a container, the container runs in the foreground by default. 84 If you want to run the container in the background instead, you can use the 85 `--detach` (or `-d`) flag. This starts the container without occupying your 86 terminal window. 87 88 ```console 89 $ docker run -d <IMAGE> 90 ``` 91 92 While the container runs in the background, you can interact with the container 93 using other CLI commands. For example, `docker logs` lets you view the logs for 94 the container, and `docker attach` brings it to the foreground. 95 96 ```console 97 $ docker run -d nginx 98 0246aa4d1448a401cabd2ce8f242192b6e7af721527e48a810463366c7ff54f1 99 $ docker ps 100 CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 101 0246aa4d1448 nginx "/docker-entrypoint.…" 2 seconds ago Up 1 second 80/tcp pedantic_liskov 102 $ docker logs -n 5 0246aa4d1448 103 2023/11/06 15:58:23 [notice] 1#1: start worker process 33 104 2023/11/06 15:58:23 [notice] 1#1: start worker process 34 105 2023/11/06 15:58:23 [notice] 1#1: start worker process 35 106 2023/11/06 15:58:23 [notice] 1#1: start worker process 36 107 2023/11/06 15:58:23 [notice] 1#1: start worker process 37 108 $ docker attach 0246aa4d1448 109 ^C 110 2023/11/06 15:58:40 [notice] 1#1: signal 2 (SIGINT) received, exiting 111 ... 112 ``` 113 114 For more information about `docker run` flags related to foreground and 115 background modes, see: 116 117 - [`docker run --detach`](https://docs.docker.com/reference/cli/docker/container/run/#detach): run container in background 118 - [`docker run --attach`](https://docs.docker.com/reference/cli/docker/container/run/#attach): attach to `stdin`, `stdout`, and `stderr` 119 - [`docker run --tty`](https://docs.docker.com/reference/cli/docker/container/run/#tty): allocate a pseudo-tty 120 - [`docker run --interactive`](https://docs.docker.com/reference/cli/docker/container/run/#interactive): keep `stdin` open even if not attached 121 122 For more information about re-attaching to a background container, see 123 [`docker attach`](https://docs.docker.com/reference/cli/docker/container/attach/). 124 125 ## Container identification 126 127 You can identify a container in three ways: 128 129 | Identifier type | Example value | 130 |:----------------------|:-------------------------------------------------------------------| 131 | UUID long identifier | `f78375b1c487e03c9438c729345e54db9d20cfa2ac1fc3494b6eb60872e74778` | 132 | UUID short identifier | `f78375b1c487` | 133 | Name | `evil_ptolemy` | 134 135 The UUID identifier is a random ID assigned to the container by the daemon. 136 137 The daemon generates a random string name for containers automatically. You can 138 also defined a custom name using [the `--name` flag](https://docs.docker.com/reference/cli/docker/container/run/#name). 139 Defining a `name` can be a handy way to add meaning to a container. If you 140 specify a `name`, you can use it when referring to the container in a 141 user-defined network. This works for both background and foreground Docker 142 containers. 143 144 A container identifier is not the same thing as an image reference. The image 145 reference specifies which image to use when you run a container. You can't run 146 `docker exec nginx:alpine sh` to open a shell in a container based on the 147 `nginx:alpine` image, because `docker exec` expects a container identifier 148 (name or ID), not an image. 149 150 While the image used by a container is not an identifier for the container, you 151 find out the IDs of containers using an image by using the `--filter` flag. For 152 example, the following `docker ps` command gets the IDs of all running 153 containers based on the `nginx:alpine` image: 154 155 ```console 156 $ docker ps -q --filter ancestor=nginx:alpine 157 ``` 158 159 For more information about using filters, see 160 [Filtering](https://docs.docker.com/config/filter/). 161 162 ## Container networking 163 164 Containers have networking enabled by default, and they can make outgoing 165 connections. If you're running multiple containers that need to communicate 166 with each other, you can create a custom network and attach the containers to 167 the network. 168 169 When multiple containers are attached to the same custom network, they can 170 communicate with each other using the container names as a DNS hostname. The 171 following example creates a custom network named `my-net`, and runs two 172 containers that attach to the network. 173 174 ```console 175 $ docker network create my-net 176 $ docker run -d --name web --network my-net nginx:alpine 177 $ docker run --rm -it --network my-net busybox 178 / # ping web 179 PING web (172.18.0.2): 56 data bytes 180 64 bytes from 172.18.0.2: seq=0 ttl=64 time=0.326 ms 181 64 bytes from 172.18.0.2: seq=1 ttl=64 time=0.257 ms 182 64 bytes from 172.18.0.2: seq=2 ttl=64 time=0.281 ms 183 ^C 184 --- web ping statistics --- 185 3 packets transmitted, 3 packets received, 0% packet loss 186 round-trip min/avg/max = 0.257/0.288/0.326 ms 187 ``` 188 189 For more information about container networking, see [Networking 190 overview](https://docs.docker.com/network/) 191 192 ## Filesystem mounts 193 194 By default, the data in a container is stored in an ephemeral, writable 195 container layer. Removing the container also removes its data. If you want to 196 use persistent data with containers, you can use filesystem mounts to store the 197 data persistently on the host system. Filesystem mounts can also let you share 198 data between containers and the host. 199 200 Docker supports two main categories of mounts: 201 202 - Volume mounts 203 - Bind mounts 204 205 Volume mounts are great for persistently storing data for containers, and for 206 sharing data between containers. Bind mounts, on the other hand, are for 207 sharing data between a container and the host. 208 209 You can add a filesystem mount to a container using the `--mount` flag for the 210 `docker run` command. 211 212 The following sections show basic examples of how to create volumes and bind 213 mounts. For more in-depth examples and descriptions, refer to the section of 214 the [storage section](https://docs.docker.com/storage/) in the documentation. 215 216 ### Volume mounts 217 218 To create a volume mount: 219 220 ```console 221 $ docker run --mount source=<VOLUME_NAME>,target=[PATH] [IMAGE] [COMMAND...] 222 ``` 223 224 The `--mount` flag takes two parameters in this case: `source` and `target`. 225 The value for the `source` parameter is the name of the volume. The value of 226 `target` is the mount location of the volume inside the container. Once you've 227 created the volume, any data you write to the volume is persisted, even if you 228 stop or remove the container: 229 230 ```console 231 $ docker run --rm --mount source=my_volume,target=/foo busybox \ 232 echo "hello, volume!" > /foo/hello.txt 233 $ docker run --mount source=my_volume,target=/bar busybox 234 cat /bar/hello.txt 235 hello, volume! 236 ``` 237 238 The `target` must always be an absolute path, such as `/src/docs`. An absolute 239 path starts with a `/` (forward slash). Volume names must start with an 240 alphanumeric character, followed by `a-z0-9`, `_` (underscore), `.` (period) or 241 `-` (hyphen). 242 243 ### Bind mounts 244 245 To create a bind mount: 246 247 ```console 248 $ docker run -it --mount type=bind,source=[PATH],target=[PATH] busybox 249 ``` 250 251 In this case, the `--mount` flag takes three parameters. A type (`bind`), and 252 two paths. The `source` path is a the location on the host that you want to 253 bind mount into the container. The `target` path is the mount destination 254 inside the container. 255 256 Bind mounts are read-write by default, meaning that you can both read and write 257 files to and from the mounted location from the container. Changes that you 258 make, such as adding or editing files, are reflected on the host filesystem: 259 260 ```console 261 $ docker run -it --mount type=bind,source=.,target=/foo busybox 262 / # echo "hello from container" > /foo/hello.txt 263 / # exit 264 $ cat hello.txt 265 hello from container 266 ``` 267 268 ## Exit status 269 270 The exit code from `docker run` gives information about why the container 271 failed to run or why it exited. The following sections describe the meanings of 272 different container exit codes values. 273 274 ### 125 275 276 Exit code `125` indicates that the error is with Docker daemon itself. 277 278 ```console 279 $ docker run --foo busybox; echo $? 280 281 flag provided but not defined: --foo 282 See 'docker run --help'. 283 125 284 ``` 285 286 ### 126 287 288 Exit code `126` indicates that the specified contained command can't be invoked. 289 The container command in the following example is: `/etc; echo $?`. 290 291 ```console 292 $ docker run busybox /etc; echo $? 293 294 docker: Error response from daemon: Container command '/etc' could not be invoked. 295 126 296 ``` 297 298 ### 127 299 300 Exit code `127` indicates that the contained command can't be found. 301 302 ```console 303 $ docker run busybox foo; echo $? 304 305 docker: Error response from daemon: Container command 'foo' not found or does not exist. 306 127 307 ``` 308 309 ### Other exit codes 310 311 Any exit code other than `125`, `126`, and `127` represent the exit code of the 312 provided container command. 313 314 ```console 315 $ docker run busybox /bin/sh -c 'exit 3' 316 $ echo $? 317 3 318 ``` 319 320 ## Runtime constraints on resources 321 322 The operator can also adjust the performance parameters of the 323 container: 324 325 | Option | Description | 326 |:---------------------------|:-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| 327 | `-m`, `--memory=""` | Memory limit (format: `<number>[<unit>]`). Number is a positive integer. Unit can be one of `b`, `k`, `m`, or `g`. Minimum is 6M. | 328 | `--memory-swap=""` | Total memory limit (memory + swap, format: `<number>[<unit>]`). Number is a positive integer. Unit can be one of `b`, `k`, `m`, or `g`. | 329 | `--memory-reservation=""` | Memory soft limit (format: `<number>[<unit>]`). Number is a positive integer. Unit can be one of `b`, `k`, `m`, or `g`. | 330 | `--kernel-memory=""` | Kernel memory limit (format: `<number>[<unit>]`). Number is a positive integer. Unit can be one of `b`, `k`, `m`, or `g`. Minimum is 4M. | 331 | `-c`, `--cpu-shares=0` | CPU shares (relative weight) | 332 | `--cpus=0.000` | Number of CPUs. Number is a fractional number. 0.000 means no limit. | 333 | `--cpu-period=0` | Limit the CPU CFS (Completely Fair Scheduler) period | 334 | `--cpuset-cpus=""` | CPUs in which to allow execution (0-3, 0,1) | 335 | `--cpuset-mems=""` | Memory nodes (MEMs) in which to allow execution (0-3, 0,1). Only effective on NUMA systems. | 336 | `--cpu-quota=0` | Limit the CPU CFS (Completely Fair Scheduler) quota | 337 | `--cpu-rt-period=0` | Limit the CPU real-time period. In microseconds. Requires parent cgroups be set and cannot be higher than parent. Also check rtprio ulimits. | 338 | `--cpu-rt-runtime=0` | Limit the CPU real-time runtime. In microseconds. Requires parent cgroups be set and cannot be higher than parent. Also check rtprio ulimits. | 339 | `--blkio-weight=0` | Block IO weight (relative weight) accepts a weight value between 10 and 1000. | 340 | `--blkio-weight-device=""` | Block IO weight (relative device weight, format: `DEVICE_NAME:WEIGHT`) | 341 | `--device-read-bps=""` | Limit read rate from a device (format: `<device-path>:<number>[<unit>]`). Number is a positive integer. Unit can be one of `kb`, `mb`, or `gb`. | 342 | `--device-write-bps=""` | Limit write rate to a device (format: `<device-path>:<number>[<unit>]`). Number is a positive integer. Unit can be one of `kb`, `mb`, or `gb`. | 343 | `--device-read-iops="" ` | Limit read rate (IO per second) from a device (format: `<device-path>:<number>`). Number is a positive integer. | 344 | `--device-write-iops="" ` | Limit write rate (IO per second) to a device (format: `<device-path>:<number>`). Number is a positive integer. | 345 | `--oom-kill-disable=false` | Whether to disable OOM Killer for the container or not. | 346 | `--oom-score-adj=0` | Tune container's OOM preferences (-1000 to 1000) | 347 | `--memory-swappiness=""` | Tune a container's memory swappiness behavior. Accepts an integer between 0 and 100. | 348 | `--shm-size=""` | Size of `/dev/shm`. The format is `<number><unit>`. `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`. | 349 350 ### User memory constraints 351 352 We have four ways to set user memory usage: 353 354 <table> 355 <thead> 356 <tr> 357 <th>Option</th> 358 <th>Result</th> 359 </tr> 360 </thead> 361 <tbody> 362 <tr> 363 <td class="no-wrap"> 364 <strong>memory=inf, memory-swap=inf</strong> (default) 365 </td> 366 <td> 367 There is no memory limit for the container. The container can use 368 as much memory as needed. 369 </td> 370 </tr> 371 <tr> 372 <td class="no-wrap"><strong>memory=L<inf, memory-swap=inf</strong></td> 373 <td> 374 (specify memory and set memory-swap as <code>-1</code>) The container is 375 not allowed to use more than L bytes of memory, but can use as much swap 376 as is needed (if the host supports swap memory). 377 </td> 378 </tr> 379 <tr> 380 <td class="no-wrap"><strong>memory=L<inf, memory-swap=2*L</strong></td> 381 <td> 382 (specify memory without memory-swap) The container is not allowed to 383 use more than L bytes of memory, swap <i>plus</i> memory usage is double 384 of that. 385 </td> 386 </tr> 387 <tr> 388 <td class="no-wrap"> 389 <strong>memory=L<inf, memory-swap=S<inf, L<=S</strong> 390 </td> 391 <td> 392 (specify both memory and memory-swap) The container is not allowed to 393 use more than L bytes of memory, swap <i>plus</i> memory usage is limited 394 by S. 395 </td> 396 </tr> 397 </tbody> 398 </table> 399 400 Examples: 401 402 ```console 403 $ docker run -it ubuntu:22.04 /bin/bash 404 ``` 405 406 We set nothing about memory, this means the processes in the container can use 407 as much memory and swap memory as they need. 408 409 ```console 410 $ docker run -it -m 300M --memory-swap -1 ubuntu:22.04 /bin/bash 411 ``` 412 413 We set memory limit and disabled swap memory limit, this means the processes in 414 the container can use 300M memory and as much swap memory as they need (if the 415 host supports swap memory). 416 417 ```console 418 $ docker run -it -m 300M ubuntu:22.04 /bin/bash 419 ``` 420 421 We set memory limit only, this means the processes in the container can use 422 300M memory and 300M swap memory, by default, the total virtual memory size 423 (--memory-swap) will be set as double of memory, in this case, memory + swap 424 would be 2*300M, so processes can use 300M swap memory as well. 425 426 ```console 427 $ docker run -it -m 300M --memory-swap 1G ubuntu:22.04 /bin/bash 428 ``` 429 430 We set both memory and swap memory, so the processes in the container can use 431 300M memory and 700M swap memory. 432 433 Memory reservation is a kind of memory soft limit that allows for greater 434 sharing of memory. Under normal circumstances, containers can use as much of 435 the memory as needed and are constrained only by the hard limits set with the 436 `-m`/`--memory` option. When memory reservation is set, Docker detects memory 437 contention or low memory and forces containers to restrict their consumption to 438 a reservation limit. 439 440 Always set the memory reservation value below the hard limit, otherwise the hard 441 limit takes precedence. A reservation of 0 is the same as setting no 442 reservation. By default (without reservation set), memory reservation is the 443 same as the hard memory limit. 444 445 Memory reservation is a soft-limit feature and does not guarantee the limit 446 won't be exceeded. Instead, the feature attempts to ensure that, when memory is 447 heavily contended for, memory is allocated based on the reservation hints/setup. 448 449 The following example limits the memory (`-m`) to 500M and sets the memory 450 reservation to 200M. 451 452 ```console 453 $ docker run -it -m 500M --memory-reservation 200M ubuntu:22.04 /bin/bash 454 ``` 455 456 Under this configuration, when the container consumes memory more than 200M and 457 less than 500M, the next system memory reclaim attempts to shrink container 458 memory below 200M. 459 460 The following example set memory reservation to 1G without a hard memory limit. 461 462 ```console 463 $ docker run -it --memory-reservation 1G ubuntu:22.04 /bin/bash 464 ``` 465 466 The container can use as much memory as it needs. The memory reservation setting 467 ensures the container doesn't consume too much memory for long time, because 468 every memory reclaim shrinks the container's consumption to the reservation. 469 470 By default, kernel kills processes in a container if an out-of-memory (OOM) 471 error occurs. To change this behaviour, use the `--oom-kill-disable` option. 472 Only disable the OOM killer on containers where you have also set the 473 `-m/--memory` option. If the `-m` flag is not set, this can result in the host 474 running out of memory and require killing the host's system processes to free 475 memory. 476 477 The following example limits the memory to 100M and disables the OOM killer for 478 this container: 479 480 ```console 481 $ docker run -it -m 100M --oom-kill-disable ubuntu:22.04 /bin/bash 482 ``` 483 484 The following example, illustrates a dangerous way to use the flag: 485 486 ```console 487 $ docker run -it --oom-kill-disable ubuntu:22.04 /bin/bash 488 ``` 489 490 The container has unlimited memory which can cause the host to run out memory 491 and require killing system processes to free memory. The `--oom-score-adj` 492 parameter can be changed to select the priority of which containers will 493 be killed when the system is out of memory, with negative scores making them 494 less likely to be killed, and positive scores more likely. 495 496 ### Kernel memory constraints 497 498 Kernel memory is fundamentally different than user memory as kernel memory can't 499 be swapped out. The inability to swap makes it possible for the container to 500 block system services by consuming too much kernel memory. Kernel memory includes: 501 502 - stack pages 503 - slab pages 504 - sockets memory pressure 505 - tcp memory pressure 506 507 You can setup kernel memory limit to constrain these kinds of memory. For example, 508 every process consumes some stack pages. By limiting kernel memory, you can 509 prevent new processes from being created when the kernel memory usage is too high. 510 511 Kernel memory is never completely independent of user memory. Instead, you limit 512 kernel memory in the context of the user memory limit. Assume "U" is the user memory 513 limit and "K" the kernel limit. There are three possible ways to set limits: 514 515 <table> 516 <thead> 517 <tr> 518 <th>Option</th> 519 <th>Result</th> 520 </tr> 521 </thead> 522 <tbody> 523 <tr> 524 <td class="no-wrap"><strong>U != 0, K = inf</strong> (default)</td> 525 <td> 526 This is the standard memory limitation mechanism already present before using 527 kernel memory. Kernel memory is completely ignored. 528 </td> 529 </tr> 530 <tr> 531 <td class="no-wrap"><strong>U != 0, K < U</strong></td> 532 <td> 533 Kernel memory is a subset of the user memory. This setup is useful in 534 deployments where the total amount of memory per-cgroup is overcommitted. 535 Overcommitting kernel memory limits is definitely not recommended, since the 536 box can still run out of non-reclaimable memory. 537 In this case, you can configure K so that the sum of all groups is 538 never greater than the total memory. Then, freely set U at the expense of 539 the system's service quality. 540 </td> 541 </tr> 542 <tr> 543 <td class="no-wrap"><strong>U != 0, K > U</strong></td> 544 <td> 545 Since kernel memory charges are also fed to the user counter and reclamation 546 is triggered for the container for both kinds of memory. This configuration 547 gives the admin a unified view of memory. It is also useful for people 548 who just want to track kernel memory usage. 549 </td> 550 </tr> 551 </tbody> 552 </table> 553 554 Examples: 555 556 ```console 557 $ docker run -it -m 500M --kernel-memory 50M ubuntu:22.04 /bin/bash 558 ``` 559 560 We set memory and kernel memory, so the processes in the container can use 561 500M memory in total, in this 500M memory, it can be 50M kernel memory tops. 562 563 ```console 564 $ docker run -it --kernel-memory 50M ubuntu:22.04 /bin/bash 565 ``` 566 567 We set kernel memory without **-m**, so the processes in the container can 568 use as much memory as they want, but they can only use 50M kernel memory. 569 570 ### Swappiness constraint 571 572 By default, a container's kernel can swap out a percentage of anonymous pages. 573 To set this percentage for a container, specify a `--memory-swappiness` value 574 between 0 and 100. A value of 0 turns off anonymous page swapping. A value of 575 100 sets all anonymous pages as swappable. By default, if you are not using 576 `--memory-swappiness`, memory swappiness value will be inherited from the parent. 577 578 For example, you can set: 579 580 ```console 581 $ docker run -it --memory-swappiness=0 ubuntu:22.04 /bin/bash 582 ``` 583 584 Setting the `--memory-swappiness` option is helpful when you want to retain the 585 container's working set and to avoid swapping performance penalties. 586 587 ### CPU share constraint 588 589 By default, all containers get the same proportion of CPU cycles. This proportion 590 can be modified by changing the container's CPU share weighting relative 591 to the weighting of all other running containers. 592 593 To modify the proportion from the default of 1024, use the `-c` or `--cpu-shares` 594 flag to set the weighting to 2 or higher. If 0 is set, the system will ignore the 595 value and use the default of 1024. 596 597 The proportion will only apply when CPU-intensive processes are running. 598 When tasks in one container are idle, other containers can use the 599 left-over CPU time. The actual amount of CPU time will vary depending on 600 the number of containers running on the system. 601 602 For example, consider three containers, one has a cpu-share of 1024 and 603 two others have a cpu-share setting of 512. When processes in all three 604 containers attempt to use 100% of CPU, the first container would receive 605 50% of the total CPU time. If you add a fourth container with a cpu-share 606 of 1024, the first container only gets 33% of the CPU. The remaining containers 607 receive 16.5%, 16.5% and 33% of the CPU. 608 609 On a multi-core system, the shares of CPU time are distributed over all CPU 610 cores. Even if a container is limited to less than 100% of CPU time, it can 611 use 100% of each individual CPU core. 612 613 For example, consider a system with more than three cores. If you start one 614 container `{C0}` with `-c=512` running one process, and another container 615 `{C1}` with `-c=1024` running two processes, this can result in the following 616 division of CPU shares: 617 618 PID container CPU CPU share 619 100 {C0} 0 100% of CPU0 620 101 {C1} 1 100% of CPU1 621 102 {C1} 2 100% of CPU2 622 623 ### CPU period constraint 624 625 The default CPU CFS (Completely Fair Scheduler) period is 100ms. We can use 626 `--cpu-period` to set the period of CPUs to limit the container's CPU usage. 627 And usually `--cpu-period` should work with `--cpu-quota`. 628 629 Examples: 630 631 ```console 632 $ docker run -it --cpu-period=50000 --cpu-quota=25000 ubuntu:22.04 /bin/bash 633 ``` 634 635 If there is 1 CPU, this means the container can get 50% CPU worth of run-time every 50ms. 636 637 In addition to use `--cpu-period` and `--cpu-quota` for setting CPU period constraints, 638 it is possible to specify `--cpus` with a float number to achieve the same purpose. 639 For example, if there is 1 CPU, then `--cpus=0.5` will achieve the same result as 640 setting `--cpu-period=50000` and `--cpu-quota=25000` (50% CPU). 641 642 The default value for `--cpus` is `0.000`, which means there is no limit. 643 644 For more information, see the [CFS documentation on bandwidth limiting](https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt). 645 646 ### Cpuset constraint 647 648 We can set cpus in which to allow execution for containers. 649 650 Examples: 651 652 ```console 653 $ docker run -it --cpuset-cpus="1,3" ubuntu:22.04 /bin/bash 654 ``` 655 656 This means processes in container can be executed on cpu 1 and cpu 3. 657 658 ```console 659 $ docker run -it --cpuset-cpus="0-2" ubuntu:22.04 /bin/bash 660 ``` 661 662 This means processes in container can be executed on cpu 0, cpu 1 and cpu 2. 663 664 We can set mems in which to allow execution for containers. Only effective 665 on NUMA systems. 666 667 Examples: 668 669 ```console 670 $ docker run -it --cpuset-mems="1,3" ubuntu:22.04 /bin/bash 671 ``` 672 673 This example restricts the processes in the container to only use memory from 674 memory nodes 1 and 3. 675 676 ```console 677 $ docker run -it --cpuset-mems="0-2" ubuntu:22.04 /bin/bash 678 ``` 679 680 This example restricts the processes in the container to only use memory from 681 memory nodes 0, 1 and 2. 682 683 ### CPU quota constraint 684 685 The `--cpu-quota` flag limits the container's CPU usage. The default 0 value 686 allows the container to take 100% of a CPU resource (1 CPU). The CFS (Completely Fair 687 Scheduler) handles resource allocation for executing processes and is default 688 Linux Scheduler used by the kernel. Set this value to 50000 to limit the container 689 to 50% of a CPU resource. For multiple CPUs, adjust the `--cpu-quota` as necessary. 690 For more information, see the [CFS documentation on bandwidth limiting](https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt). 691 692 ### Block IO bandwidth (Blkio) constraint 693 694 By default, all containers get the same proportion of block IO bandwidth 695 (blkio). This proportion is 500. To modify this proportion, change the 696 container's blkio weight relative to the weighting of all other running 697 containers using the `--blkio-weight` flag. 698 699 > **Note:** 700 > 701 > The blkio weight setting is only available for direct IO. Buffered IO is not 702 > currently supported. 703 704 The `--blkio-weight` flag can set the weighting to a value between 10 to 1000. 705 For example, the commands below create two containers with different blkio 706 weight: 707 708 ```console 709 $ docker run -it --name c1 --blkio-weight 300 ubuntu:22.04 /bin/bash 710 $ docker run -it --name c2 --blkio-weight 600 ubuntu:22.04 /bin/bash 711 ``` 712 713 If you do block IO in the two containers at the same time, by, for example: 714 715 ```console 716 $ time dd if=/mnt/zerofile of=test.out bs=1M count=1024 oflag=direct 717 ``` 718 719 You'll find that the proportion of time is the same as the proportion of blkio 720 weights of the two containers. 721 722 The `--blkio-weight-device="DEVICE_NAME:WEIGHT"` flag sets a specific device weight. 723 The `DEVICE_NAME:WEIGHT` is a string containing a colon-separated device name and weight. 724 For example, to set `/dev/sda` device weight to `200`: 725 726 ```console 727 $ docker run -it \ 728 --blkio-weight-device "/dev/sda:200" \ 729 ubuntu 730 ``` 731 732 If you specify both the `--blkio-weight` and `--blkio-weight-device`, Docker 733 uses the `--blkio-weight` as the default weight and uses `--blkio-weight-device` 734 to override this default with a new value on a specific device. 735 The following example uses a default weight of `300` and overrides this default 736 on `/dev/sda` setting that weight to `200`: 737 738 ```console 739 $ docker run -it \ 740 --blkio-weight 300 \ 741 --blkio-weight-device "/dev/sda:200" \ 742 ubuntu 743 ``` 744 745 The `--device-read-bps` flag limits the read rate (bytes per second) from a device. 746 For example, this command creates a container and limits the read rate to `1mb` 747 per second from `/dev/sda`: 748 749 ```console 750 $ docker run -it --device-read-bps /dev/sda:1mb ubuntu 751 ``` 752 753 The `--device-write-bps` flag limits the write rate (bytes per second) to a device. 754 For example, this command creates a container and limits the write rate to `1mb` 755 per second for `/dev/sda`: 756 757 ```console 758 $ docker run -it --device-write-bps /dev/sda:1mb ubuntu 759 ``` 760 761 Both flags take limits in the `<device-path>:<limit>[unit]` format. Both read 762 and write rates must be a positive integer. You can specify the rate in `kb` 763 (kilobytes), `mb` (megabytes), or `gb` (gigabytes). 764 765 The `--device-read-iops` flag limits read rate (IO per second) from a device. 766 For example, this command creates a container and limits the read rate to 767 `1000` IO per second from `/dev/sda`: 768 769 ```console 770 $ docker run -ti --device-read-iops /dev/sda:1000 ubuntu 771 ``` 772 773 The `--device-write-iops` flag limits write rate (IO per second) to a device. 774 For example, this command creates a container and limits the write rate to 775 `1000` IO per second to `/dev/sda`: 776 777 ```console 778 $ docker run -ti --device-write-iops /dev/sda:1000 ubuntu 779 ``` 780 781 Both flags take limits in the `<device-path>:<limit>` format. Both read and 782 write rates must be a positive integer. 783 784 ## Additional groups 785 786 ```console 787 --group-add: Add additional groups to run as 788 ``` 789 790 By default, the docker container process runs with the supplementary groups looked 791 up for the specified user. If one wants to add more to that list of groups, then 792 one can use this flag: 793 794 ```console 795 $ docker run --rm --group-add audio --group-add nogroup --group-add 777 busybox id 796 797 uid=0(root) gid=0(root) groups=10(wheel),29(audio),99(nogroup),777 798 ``` 799 800 ## Runtime privilege and Linux capabilities 801 802 | Option | Description | 803 |:---------------|:------------------------------------------------------------------------------| 804 | `--cap-add` | Add Linux capabilities | 805 | `--cap-drop` | Drop Linux capabilities | 806 | `--privileged` | Give extended privileges to this container | 807 | `--device=[]` | Allows you to run devices inside the container without the `--privileged` flag. | 808 809 By default, Docker containers are "unprivileged" and cannot, for 810 example, run a Docker daemon inside a Docker container. This is because 811 by default a container is not allowed to access any devices, but a 812 "privileged" container is given access to all devices (see 813 the documentation on [cgroups devices](https://www.kernel.org/doc/Documentation/cgroup-v1/devices.txt)). 814 815 The `--privileged` flag gives all capabilities to the container. When the operator 816 executes `docker run --privileged`, Docker will enable access to all devices on 817 the host as well as set some configuration in AppArmor or SELinux to allow the 818 container nearly all the same access to the host as processes running outside 819 containers on the host. Additional information about running with `--privileged` 820 is available on the [Docker Blog](https://www.docker.com/blog/docker-can-now-run-within-docker/). 821 822 If you want to limit access to a specific device or devices you can use 823 the `--device` flag. It allows you to specify one or more devices that 824 will be accessible within the container. 825 826 ```console 827 $ docker run --device=/dev/snd:/dev/snd ... 828 ``` 829 830 By default, the container will be able to `read`, `write`, and `mknod` these devices. 831 This can be overridden using a third `:rwm` set of options to each `--device` flag: 832 833 ```console 834 $ docker run --device=/dev/sda:/dev/xvdc --rm -it ubuntu fdisk /dev/xvdc 835 836 Command (m for help): q 837 $ docker run --device=/dev/sda:/dev/xvdc:r --rm -it ubuntu fdisk /dev/xvdc 838 You will not be able to write the partition table. 839 840 Command (m for help): q 841 842 $ docker run --device=/dev/sda:/dev/xvdc:w --rm -it ubuntu fdisk /dev/xvdc 843 crash.... 844 845 $ docker run --device=/dev/sda:/dev/xvdc:m --rm -it ubuntu fdisk /dev/xvdc 846 fdisk: unable to open /dev/xvdc: Operation not permitted 847 ``` 848 849 In addition to `--privileged`, the operator can have fine grain control over the 850 capabilities using `--cap-add` and `--cap-drop`. By default, Docker has a default 851 list of capabilities that are kept. The following table lists the Linux capability 852 options which are allowed by default and can be dropped. 853 854 | Capability Key | Capability Description | 855 |:----------------------|:-------------------------------------------------------------------------------------------------------------------------------| 856 | AUDIT_WRITE | Write records to kernel auditing log. | 857 | CHOWN | Make arbitrary changes to file UIDs and GIDs (see chown(2)). | 858 | DAC_OVERRIDE | Bypass file read, write, and execute permission checks. | 859 | FOWNER | Bypass permission checks on operations that normally require the file system UID of the process to match the UID of the file. | 860 | FSETID | Don't clear set-user-ID and set-group-ID permission bits when a file is modified. | 861 | KILL | Bypass permission checks for sending signals. | 862 | MKNOD | Create special files using mknod(2). | 863 | NET_BIND_SERVICE | Bind a socket to internet domain privileged ports (port numbers less than 1024). | 864 | NET_RAW | Use RAW and PACKET sockets. | 865 | SETFCAP | Set file capabilities. | 866 | SETGID | Make arbitrary manipulations of process GIDs and supplementary GID list. | 867 | SETPCAP | Modify process capabilities. | 868 | SETUID | Make arbitrary manipulations of process UIDs. | 869 | SYS_CHROOT | Use chroot(2), change root directory. | 870 871 The next table shows the capabilities which are not granted by default and may be added. 872 873 | Capability Key | Capability Description | 874 |:----------------------|:-------------------------------------------------------------------------------------------------------------------------------| 875 | AUDIT_CONTROL | Enable and disable kernel auditing; change auditing filter rules; retrieve auditing status and filtering rules. | 876 | AUDIT_READ | Allow reading the audit log via multicast netlink socket. | 877 | BLOCK_SUSPEND | Allow preventing system suspends. | 878 | BPF | Allow creating BPF maps, loading BPF Type Format (BTF) data, retrieve JITed code of BPF programs, and more. | 879 | CHECKPOINT_RESTORE | Allow checkpoint/restore related operations. Introduced in kernel 5.9. | 880 | DAC_READ_SEARCH | Bypass file read permission checks and directory read and execute permission checks. | 881 | IPC_LOCK | Lock memory (mlock(2), mlockall(2), mmap(2), shmctl(2)). | 882 | IPC_OWNER | Bypass permission checks for operations on System V IPC objects. | 883 | LEASE | Establish leases on arbitrary files (see fcntl(2)). | 884 | LINUX_IMMUTABLE | Set the FS_APPEND_FL and FS_IMMUTABLE_FL i-node flags. | 885 | MAC_ADMIN | Allow MAC configuration or state changes. Implemented for the Smack LSM. | 886 | MAC_OVERRIDE | Override Mandatory Access Control (MAC). Implemented for the Smack Linux Security Module (LSM). | 887 | NET_ADMIN | Perform various network-related operations. | 888 | NET_BROADCAST | Make socket broadcasts, and listen to multicasts. | 889 | PERFMON | Allow system performance and observability privileged operations using perf_events, i915_perf and other kernel subsystems | 890 | SYS_ADMIN | Perform a range of system administration operations. | 891 | SYS_BOOT | Use reboot(2) and kexec_load(2), reboot and load a new kernel for later execution. | 892 | SYS_MODULE | Load and unload kernel modules. | 893 | SYS_NICE | Raise process nice value (nice(2), setpriority(2)) and change the nice value for arbitrary processes. | 894 | SYS_PACCT | Use acct(2), switch process accounting on or off. | 895 | SYS_PTRACE | Trace arbitrary processes using ptrace(2). | 896 | SYS_RAWIO | Perform I/O port operations (iopl(2) and ioperm(2)). | 897 | SYS_RESOURCE | Override resource Limits. | 898 | SYS_TIME | Set system clock (settimeofday(2), stime(2), adjtimex(2)); set real-time (hardware) clock. | 899 | SYS_TTY_CONFIG | Use vhangup(2); employ various privileged ioctl(2) operations on virtual terminals. | 900 | SYSLOG | Perform privileged syslog(2) operations. | 901 | WAKE_ALARM | Trigger something that will wake up the system. | 902 903 Further reference information is available on the [capabilities(7) - Linux man page](https://man7.org/linux/man-pages/man7/capabilities.7.html), 904 and in the [Linux kernel source code](https://github.com/torvalds/linux/blob/124ea650d3072b005457faed69909221c2905a1f/include/uapi/linux/capability.h). 905 906 Both flags support the value `ALL`, so to allow a container to use all capabilities 907 except for `MKNOD`: 908 909 ```console 910 $ docker run --cap-add=ALL --cap-drop=MKNOD ... 911 ``` 912 913 The `--cap-add` and `--cap-drop` flags accept capabilities to be specified with 914 a `CAP_` prefix. The following examples are therefore equivalent: 915 916 ```console 917 $ docker run --cap-add=SYS_ADMIN ... 918 $ docker run --cap-add=CAP_SYS_ADMIN ... 919 ``` 920 921 For interacting with the network stack, instead of using `--privileged` they 922 should use `--cap-add=NET_ADMIN` to modify the network interfaces. 923 924 ```console 925 $ docker run -it --rm ubuntu:22.04 ip link add dummy0 type dummy 926 927 RTNETLINK answers: Operation not permitted 928 929 $ docker run -it --rm --cap-add=NET_ADMIN ubuntu:22.04 ip link add dummy0 type dummy 930 ``` 931 932 To mount a FUSE based filesystem, you need to combine both `--cap-add` and 933 `--device`: 934 935 ```console 936 $ docker run --rm -it --cap-add SYS_ADMIN sshfs sshfs sven@10.10.10.20:/home/sven /mnt 937 938 fuse: failed to open /dev/fuse: Operation not permitted 939 940 $ docker run --rm -it --device /dev/fuse sshfs sshfs sven@10.10.10.20:/home/sven /mnt 941 942 fusermount: mount failed: Operation not permitted 943 944 $ docker run --rm -it --cap-add SYS_ADMIN --device /dev/fuse sshfs 945 946 # sshfs sven@10.10.10.20:/home/sven /mnt 947 The authenticity of host '10.10.10.20 (10.10.10.20)' can't be established. 948 ECDSA key fingerprint is 25:34:85:75:25:b0:17:46:05:19:04:93:b5:dd:5f:c6. 949 Are you sure you want to continue connecting (yes/no)? yes 950 sven@10.10.10.20's password: 951 952 root@30aa0cfaf1b5:/# ls -la /mnt/src/docker 953 954 total 1516 955 drwxrwxr-x 1 1000 1000 4096 Dec 4 06:08 . 956 drwxrwxr-x 1 1000 1000 4096 Dec 4 11:46 .. 957 -rw-rw-r-- 1 1000 1000 16 Oct 8 00:09 .dockerignore 958 -rwxrwxr-x 1 1000 1000 464 Oct 8 00:09 .drone.yml 959 drwxrwxr-x 1 1000 1000 4096 Dec 4 06:11 .git 960 -rw-rw-r-- 1 1000 1000 461 Dec 4 06:08 .gitignore 961 .... 962 ``` 963 964 The default seccomp profile will adjust to the selected capabilities, in order to allow 965 use of facilities allowed by the capabilities, so you should not have to adjust this. 966 967 ## Overriding image defaults 968 969 When you build an image from a [Dockerfile](https://docs.docker.com/reference/dockerfile/), 970 or when committing it, you can set a number of default parameters that take 971 effect when the image starts up as a container. When you run an image, you can 972 override those defaults using flags for the `docker run` command. 973 974 - [Default entrypoint](#default-entrypoint) 975 - [Default command and options](#default-command-and-options) 976 - [Expose ports](#exposed-ports) 977 - [Environment variables](#environment-variables) 978 - [Healthcheck](#healthchecks) 979 - [User](#user) 980 - [Working directory](#working-directory) 981 982 ### Default command and options 983 984 The command syntax for `docker run` supports optionally specifying commands and 985 arguments to the container's entrypoint, represented as `[COMMAND]` and 986 `[ARG...]` in the following synopsis example: 987 988 ```console 989 $ docker run [OPTIONS] IMAGE[:TAG|@DIGEST] [COMMAND] [ARG...] 990 ``` 991 992 This command is optional because whoever created the `IMAGE` may have already 993 provided a default `COMMAND`, using the Dockerfile `CMD` instruction. When you 994 run a container, you can override that `CMD` instruction just by specifying a 995 new `COMMAND`. 996 997 If the image also specifies an `ENTRYPOINT` then the `CMD` or `COMMAND` 998 get appended as arguments to the `ENTRYPOINT`. 999 1000 ### Default entrypoint 1001 1002 ```text 1003 --entrypoint="": Overwrite the default entrypoint set by the image 1004 ``` 1005 1006 The entrypoint refers to the default executable that's invoked when you run a 1007 container. A container's entrypoint is defined using the Dockerfile 1008 `ENTRYPOINT` instruction. It's similar to specifying a default command because 1009 it specifies, but the difference is that you need to pass an explicit flag to 1010 override the entrypoint, whereas you can override default commands with 1011 positional arguments. The defines a container's default behavior, with the idea 1012 that when you set an entrypoint you can run the container *as if it were that 1013 binary*, complete with default options, and you can pass in more options as 1014 commands. But there are cases where you may want to run something else inside 1015 the container. This is when overriding the default entrypoint at runtime comes 1016 in handy, using the `--entrypoint` flag for the `docker run` command. 1017 1018 The `--entrypoint` flag expects a string value, representing the name or path 1019 of the binary that you want to invoke when the container starts. The following 1020 example shows you how to run a Bash shell in a container that has been set up 1021 to automatically run some other binary (like `/usr/bin/redis-server`): 1022 1023 ```console 1024 $ docker run -it --entrypoint /bin/bash example/redis 1025 ``` 1026 1027 The following examples show how to pass additional parameters to the custom 1028 entrypoint, using the positional command arguments: 1029 1030 ```console 1031 $ docker run -it --entrypoint /bin/bash example/redis -c ls -l 1032 $ docker run -it --entrypoint /usr/bin/redis-cli example/redis --help 1033 ``` 1034 1035 You can reset a containers entrypoint by passing an empty string, for example: 1036 1037 ```console 1038 $ docker run -it --entrypoint="" mysql bash 1039 ``` 1040 1041 > **Note** 1042 > 1043 > Passing `--entrypoint` clears out any default command set on the image. That 1044 > is, any `CMD` instruction in the Dockerfile used to build it. 1045 1046 ### Exposed ports 1047 1048 By default, when you run a container, none of the container's ports are exposed 1049 to the host. This means you won't be able to access any ports that the 1050 container might be listening on. To make a container's ports accessible from 1051 the host, you need to publish the ports. 1052 1053 You can start the container with the `-P` or `-p` flags to expose its ports: 1054 1055 - The `-P` (or `--publish-all`) flag publishes all the exposed ports to the 1056 host. Docker binds each exposed port to a random port on the host. 1057 1058 The `-P` flag only publishes port numbers that are explicitly flagged as 1059 exposed, either using the Dockerfile `EXPOSE` instruction or the `--expose` 1060 flag for the `docker run` command. 1061 1062 - The `-p` (or `--publish`) flag lets you explicitly map a single port or range 1063 of ports in the container to the host. 1064 1065 The port number inside the container (where the service listens) doesn't need 1066 to match the port number published on the outside of the container (where 1067 clients connect). For example, inside the container an HTTP service might be 1068 listening on port 80. At runtime, the port might be bound to 42800 on the host. 1069 To find the mapping between the host ports and the exposed ports, use the 1070 `docker port` command. 1071 1072 ### Environment variables 1073 1074 Docker automatically sets some environment variables when creating a Linux 1075 container. Docker doesn't set any environment variables when creating a Windows 1076 container. 1077 1078 The following environment variables are set for Linux containers: 1079 1080 | Variable | Value | 1081 |:-----------|:-----------------------------------------------------------------------------------------------------| 1082 | `HOME` | Set based on the value of `USER` | 1083 | `HOSTNAME` | The hostname associated with the container | 1084 | `PATH` | Includes popular directories, such as `/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin` | 1085 | `TERM` | `xterm` if the container is allocated a pseudo-TTY | 1086 1087 1088 Additionally, you can set any environment variable in the container by using 1089 one or more `-e` flags. You can even override the variables mentioned above, or 1090 variables defined using a Dockerfile `ENV` instruction when building the image. 1091 1092 If the you name an environment variable without specifying a value, the current 1093 value of the named variable on the host is propagated into the container's 1094 environment: 1095 1096 ```console 1097 $ export today=Wednesday 1098 $ docker run -e "deep=purple" -e today --rm alpine env 1099 1100 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin 1101 HOSTNAME=d2219b854598 1102 deep=purple 1103 today=Wednesday 1104 HOME=/root 1105 ``` 1106 1107 ```powershell 1108 PS C:\> docker run --rm -e "foo=bar" microsoft/nanoserver cmd /s /c set 1109 ALLUSERSPROFILE=C:\ProgramData 1110 APPDATA=C:\Users\ContainerAdministrator\AppData\Roaming 1111 CommonProgramFiles=C:\Program Files\Common Files 1112 CommonProgramFiles(x86)=C:\Program Files (x86)\Common Files 1113 CommonProgramW6432=C:\Program Files\Common Files 1114 COMPUTERNAME=C2FAEFCC8253 1115 ComSpec=C:\Windows\system32\cmd.exe 1116 foo=bar 1117 LOCALAPPDATA=C:\Users\ContainerAdministrator\AppData\Local 1118 NUMBER_OF_PROCESSORS=8 1119 OS=Windows_NT 1120 Path=C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Users\ContainerAdministrator\AppData\Local\Microsoft\WindowsApps 1121 PATHEXT=.COM;.EXE;.BAT;.CMD 1122 PROCESSOR_ARCHITECTURE=AMD64 1123 PROCESSOR_IDENTIFIER=Intel64 Family 6 Model 62 Stepping 4, GenuineIntel 1124 PROCESSOR_LEVEL=6 1125 PROCESSOR_REVISION=3e04 1126 ProgramData=C:\ProgramData 1127 ProgramFiles=C:\Program Files 1128 ProgramFiles(x86)=C:\Program Files (x86) 1129 ProgramW6432=C:\Program Files 1130 PROMPT=$P$G 1131 PUBLIC=C:\Users\Public 1132 SystemDrive=C: 1133 SystemRoot=C:\Windows 1134 TEMP=C:\Users\ContainerAdministrator\AppData\Local\Temp 1135 TMP=C:\Users\ContainerAdministrator\AppData\Local\Temp 1136 USERDOMAIN=User Manager 1137 USERNAME=ContainerAdministrator 1138 USERPROFILE=C:\Users\ContainerAdministrator 1139 windir=C:\Windows 1140 ``` 1141 1142 ### Healthchecks 1143 1144 The following flags for the `docker run` command let you control the parameters 1145 for container healthchecks: 1146 1147 | Option | Description | 1148 |:---------------------------|:---------------------------------------------------------------------------------------| 1149 | `--health-cmd` | Command to run to check health | 1150 | `--health-interval` | Time between running the check | 1151 | `--health-retries` | Consecutive failures needed to report unhealthy | 1152 | `--health-timeout` | Maximum time to allow one check to run | 1153 | `--health-start-period` | Start period for the container to initialize before starting health-retries countdown | 1154 | `--health-start-interval` | Time between running the check during the start period | 1155 | `--no-healthcheck` | Disable any container-specified `HEALTHCHECK` | 1156 1157 Example: 1158 1159 ```console 1160 $ docker run --name=test -d \ 1161 --health-cmd='stat /etc/passwd || exit 1' \ 1162 --health-interval=2s \ 1163 busybox sleep 1d 1164 $ sleep 2; docker inspect --format='{{.State.Health.Status}}' test 1165 healthy 1166 $ docker exec test rm /etc/passwd 1167 $ sleep 2; docker inspect --format='{{json .State.Health}}' test 1168 { 1169 "Status": "unhealthy", 1170 "FailingStreak": 3, 1171 "Log": [ 1172 { 1173 "Start": "2016-05-25T17:22:04.635478668Z", 1174 "End": "2016-05-25T17:22:04.7272552Z", 1175 "ExitCode": 0, 1176 "Output": " File: /etc/passwd\n Size: 334 \tBlocks: 8 IO Block: 4096 regular file\nDevice: 32h/50d\tInode: 12 Links: 1\nAccess: (0664/-rw-rw-r--) Uid: ( 0/ root) Gid: ( 0/ root)\nAccess: 2015-12-05 22:05:32.000000000\nModify: 2015..." 1177 }, 1178 { 1179 "Start": "2016-05-25T17:22:06.732900633Z", 1180 "End": "2016-05-25T17:22:06.822168935Z", 1181 "ExitCode": 0, 1182 "Output": " File: /etc/passwd\n Size: 334 \tBlocks: 8 IO Block: 4096 regular file\nDevice: 32h/50d\tInode: 12 Links: 1\nAccess: (0664/-rw-rw-r--) Uid: ( 0/ root) Gid: ( 0/ root)\nAccess: 2015-12-05 22:05:32.000000000\nModify: 2015..." 1183 }, 1184 { 1185 "Start": "2016-05-25T17:22:08.823956535Z", 1186 "End": "2016-05-25T17:22:08.897359124Z", 1187 "ExitCode": 1, 1188 "Output": "stat: can't stat '/etc/passwd': No such file or directory\n" 1189 }, 1190 { 1191 "Start": "2016-05-25T17:22:10.898802931Z", 1192 "End": "2016-05-25T17:22:10.969631866Z", 1193 "ExitCode": 1, 1194 "Output": "stat: can't stat '/etc/passwd': No such file or directory\n" 1195 }, 1196 { 1197 "Start": "2016-05-25T17:22:12.971033523Z", 1198 "End": "2016-05-25T17:22:13.082015516Z", 1199 "ExitCode": 1, 1200 "Output": "stat: can't stat '/etc/passwd': No such file or directory\n" 1201 } 1202 ] 1203 } 1204 ``` 1205 1206 The health status is also displayed in the `docker ps` output. 1207 1208 ### User 1209 1210 The default user within a container is `root` (uid = 0). You can set a default 1211 user to run the first process with the Dockerfile `USER` instruction. When 1212 starting a container, you can override the `USER` instruction by passing the 1213 `-u` option. 1214 1215 ```text 1216 -u="", --user="": Sets the username or UID used and optionally the groupname or GID for the specified command. 1217 ``` 1218 1219 The followings examples are all valid: 1220 1221 ```text 1222 --user=[ user | user:group | uid | uid:gid | user:gid | uid:group ] 1223 ``` 1224 1225 > **Note** 1226 > 1227 > If you pass a numeric user ID, it must be in the range of 0-2147483647. If 1228 > you pass a username, the user must exist in the container. 1229 1230 ### Working directory 1231 1232 The default working directory for running binaries within a container is the 1233 root directory (`/`). The default working directory of an image is set using 1234 the Dockerfile `WORKDIR` command. You can override the default working 1235 directory for an image using the `-w` (or `--workdir`) flag for the `docker 1236 run` command: 1237 1238 ```text 1239 $ docker run --rm -w /my/workdir alpine pwd 1240 /my/workdir 1241 ``` 1242 1243 If the directory doesn't already exist in the container, it's created.