Configure mount points and swap files

For a full list of keys, refer to the mounts module schema.

Create swap file

This example creates a 2 GB swap file at /swapfile using human-readable values.

1#cloud-config
2swap:
3filename:/swapfile
4size:2G
5maxsize:2G

Set mount point and create swap file

In this example we mount: - ephemeral0 with the "noexec" flag, - /dev/sdc with mount_default_fields, and - /dev/xvdh with custom fs_passno "0" to avoid fsck on the mount.

The config also provides an automatically-sized swap with a maximum size of 10485760 bytes.

 1#cloud-config
 2mounts:
 3-[/dev/ephemeral0,/mnt,auto,"defaults,noexec"]
 4-[sdc,/opt/data]
 5-[xvdh,/opt/data,auto,"defaults,nofail","0","0"]
 6mount_default_fields:[None,None,auto,"defaults,nofail","0","2"]
 7swap:
 8filename:/my/swapfile
 9size:auto
10maxsize:10485760

Explanation of fields

Let us break down some of the options available.

Mounts

Set up mount points. mounts contains a list of lists. The inner list contains entries for an /etc/fstab line, e.g.:

[fs_spec,fs_file,fs_vfstype,fs_mntops,fs_freq,fs_passno]

With defaults:

mounts:
-[ephemeral0,/mnt]
-[swap,none,swap,sw,0,0]

To remove a previously-listed mount (i.e., a default one), list only the fs_spec. For example, to override the default, of mounting swap [ swap ] or [ swap, null ].

  • If a device does not exist at the time, an entry will still be written to /etc/fstab.

  • /dev can be omitted for device names that begin with: xvd, sd, hd, or vd.

  • If an entry does not have all 6 fields, they will be filled in with values from the mount_default_fields below.

Note

You should set nofail (see man fstab) for volumes that may not be attached at instance boot (or reboot).

Example for mounts 

mounts:
-[ephemeral0,/mnt,auto,"defaults,noexec"]
-[sdc,/opt/data]
-[xvdh,/opt/data,"auto","defaults,nofail","0","0"]
-[dd,/dev/zero]

Mount default fields

The mount_default_fields values are used to fill in any incomplete entries in mounts. This must be an array, and must have 6 fields.

mount_default_fields:[None,None,"auto","defaults,nofail","0","2"]

Swap

swap can also be set up by the mounts module. The default behavior is to not create any swap files, because size is set to 0.

swap:
filename:/swap.img
size:"auto"# or size in bytes
maxsize:10485760# size in bytes