zram-init - Scripts to support compressed swap devices or ramdisks with zram

NAME SYNOPSIS DESCRIPTION OPTIONS AUTHORS SEE ALSO

NAME

zram-init − Scripts to support compressed swap devices or ramdisks with zram

SYNOPSIS

zram-init [options] SIZE|write [DIR]

Prepare a zram device and use it as swap (resp. mount it under DIR).
SIZE is the maximal size in megabytes. For umounting/freeing the zram device, use SIZE=0.
When using write (or anything else starting with w) an idle writeback is forced (only makes sense if previously initialized with -w or -W LIMIT).

If DIR is − then only a filesystem is created in /dev/zramDEV (or the device is removed if SIZE is 0), but it is not mounted (options −o −c −m −T take no effect in this case, of course).
The latter can be useful e.g. for btrfs if multiple devices should be mounted jointly afterwards.

OPTIONS

An empty argument means the same as if the option is not specified.

−d DEV

Use zram device /dev/zramDEV. Default is 0 (/dev/zram0).

Make sure to use the matching value for unmounting (SIZE=0)!

-D NUM

If modprobe needs to be used, require NUM devices.

This is not recommended. Rely instead on /etc/modprobe.d/zram.conf with the line options zram num_devices=NUM.

	−s NUM		Use up to NUM parallel compression streams for the device.
	−S MAX		Use maximally MAX megabytes of uncompressed memory for the device.
	−b DEV		Use DEV as backing device.
	−I		If combined with −b DEV, store incompressible pages to backing device.
	−w		If combined with -b DEV, enable idle writeback to backing device.

−W LIMIT

As -w but additionally set writeback_limit to LIMIT * 4kB.

−a 842|deflate|lz4|lz4hc|lzo|zstd

Set the compression algorithm to be used for compressing data in the zram device.

−c OWNER

Chown to OWNER (resp. OWNER:GROUP) after mounting.

−m MODE

Chmod DIR to MODE after mounting.

−o OPTS

Mount DIR with −o OPTS.

−p PRIO

Use priority PRIO for the swap device. Default is 16383.
Use PRIO=− if you want to keep the default priority (-1).

−t ext2|ext4|btrfs|xfs

Set the filesystem type if DIR is specified. Default is ext4.

−B BSIZE

Override default blocksize (ext2, ext4). Valid values are 1024, 2048, 4096.

−i IRATIO

Override default bytes/inodes in fs (ext2, ext4).

−N INODES

Override inode count (ext2, ext4).

−L LABEL

Specify the label LABEL for the new filesystem.

−U UUID

Specify the uuid UUID for the new filesystem.

−T

Do not use the discard (TRIM) feature of ext4/swap.

Use this option with linux-3.14 or earlier or when you want a slight speed increase at the cost of possibly wasting a lot of memory.

	−l		Do not use zramctl even if available.
	−k		Do no attempt to umount/free a previously used zram under this device.

If you have push.sh in $PATH, you can also use the following options accumulatively:

	−K ARG		Pass ARG to the respective mkswap or mkfs.* call.
	−M ARG		Pass ARG to the respective swapon/mount call.
	−2 ARG		Pass ARG to the tune2fs call (ignored unless for ext2 or ext4).
	−Z ARG		Pass ARG to the zramctl call.

Call with LANG=C to disable translations.

AUTHORS

Martin Väth <martin at mvath.de> (developer, current maintainer)