f72a2e7bef
for swap.sh, take any command-line options, not just those with an arg that in turn requires a new hash on the example Use latest 4.9.x kernel to keep in line with other examples Replace (bash) herestring with (posix) heredoc in swap.sh, and update hash to match Signed-off-by: Avi Deitcher <avi@deitcher.net>
LinuxKit Swap
Image to enable creation of a swap file for a linuxkit-generated image.
Usage
Normally, unless you are running explicitly in a desktop version, LinuxKit images do not have swap enabled. If you want swap, add the following to your moby.yml:
onboot:
- name: swap
image: "linuxkit/swap:1.0.0"
net: none
pid: host
capabilities:
- CAP_SYS_ADMIN
readonly: true
binds:
- /dev:/dev
- /var:/var
command: ["swap.sh","--path","/var/external/swap","--size","2G"]
Note that you nust mount the following:
/varto/varso it can place the swapfile in the right location./devto/devso it can do the right thing for devices
Options
Options are passed to it via command-line options. The following are the options. Details follow.
| Option | Parameter | Default | Required | Notes |
|---|---|---|---|---|
--path |
Path to file as seen in the underlying OS | Yes | ||
--size |
Target swapfile size | Yes | ||
--condition |
condition | No | Condition that must be met to create a swapfile | |
--debug |
No | Turns on verbose output from the command making the swap |
File
You can create a swapfile at the given path. You must provide exactly one swapfile path, or none will be created; there is no default. Passing fewer than or more than one --path option causes the container to exit with an error.
The option --path takes a single argument path, path to the swapfile, e.g. /var/mnt/swap2.
You always should put the swap file somewhere under /var, since that is where read-writable files and mounts exist in linuxkit images.
Size
--size <size> indicates the desired swapfile size, e.g. 2G 100M 5670K 8765432. There is no default. Acceptable size units are G, M, K and bytes of no unit provided.
If disk space on the requested partition is insufficient to create the swapfile, the container exits with an error.
Conditions
You may want to create a swapfile only if certain conditions are met. Supported conditions are:
- An external disk is available
- Partition on which the swapfile will sit is of a minimum size.
All conditions must be met. If a condition fails, the swapfile is not created, but the container exits with no error, unless you set the condition as required.
Conditions are structured as follows: type:parameter:required
In all cases, you may leave off required if you wish to treat it as false, i.e. do not create swapfile but exit with no error if the condition is not met.
Partition exists
LinuxKit may be running from a small disk, and you only want to run if a particular large external disk is available. In that case, pass --condition part:<path>:<required> to indicate that swapfile is to be created only if path already exists and is a mount point.
Example: --condition part:/var/mnt/external
Size
You may set a minimum size for a partition (likely the one on which the swapfile will be created) using the size condition of the format --condition size:<path>:<size>:<required> to indicate that swapfile is to be created only if the partition on which path exists is of minimum size size. Acceptable sizes are identical to those for the swapfile.
Examples:
--condition partsize:/var/mnt/external:100G:true
Example
An example yml file is included in examples/swap.yml. swap.yml. Note that you need to attach an external disk - trying to create a swapfile in tmpfs /var will fail.
The sample command to run the enclosed is:
moby build swap.yml
moby run -disk-size 4096 swap