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| author | Marcos Mello | 2019-03-11 11:30:35 +0100 |
|---|---|---|
| committer | Marcos Mello | 2019-03-11 11:30:35 +0100 |
| commit | 63391d7579a4bf4d3a044d14aea0ceba5b028083 (patch) | |
| tree | 9375b5c94bdab886da657781d8c5ddc6c7c50d7a /sys-utils/swapon.8 | |
| parent | Merge branch 'setterm' of https://github.com/jwilk-forks/util-linux (diff) | |
| download | kernel-qcow2-util-linux-63391d7579a4bf4d3a044d14aea0ceba5b028083.tar.gz kernel-qcow2-util-linux-63391d7579a4bf4d3a044d14aea0ceba5b028083.tar.xz kernel-qcow2-util-linux-63391d7579a4bf4d3a044d14aea0ceba5b028083.zip | |
swapon.8: mention btrfs(5)
See:
https://github.com/kdave/btrfs-progs/commit/5c880c82c2044b0abae5c838c733a2e6522ed122
Diffstat (limited to 'sys-utils/swapon.8')
| -rw-r--r-- | sys-utils/swapon.8 | 29 |
1 files changed, 14 insertions, 15 deletions
diff --git a/sys-utils/swapon.8 b/sys-utils/swapon.8 index d645850bb..d01f681f8 100644 --- a/sys-utils/swapon.8 +++ b/sys-utils/swapon.8 @@ -189,31 +189,29 @@ Be verbose. Display version information and exit. .SH NOTES .SS Files with holes -The swap file implementation in the kernel expects to be able to write to the file directly, -without the assistance of the filesystem. This is a problem on files with holes -or on copy-on-write files on filesystems like btrfs. +The swap file implementation in the kernel expects to be able to write to the +file directly, without the assistance of the filesystem. This is a problem on +files with holes or on copy-on-write files on filesystems like Btrfs. .sp -The commands like +Commands like .BR cp (1) or .BR truncate (1) create files with holes. These files will be rejected by swapon. .sp -In some cases preallocated files (e.g. fallocate(1) on XFS) maybe interpreted -by old kernel versions as files with holes too. The preallocated swap files on XFS are -supported since Linux 4.18. +Preallocated files created by +.BR fallocate (1) +may be interpreted as files with holes too depending of the filesystem. +Preallocated swap files are supported on XFS since Linux 4.18. .sp The most portable solution to create a swap file is to use .BR dd (1) -and /dev/zero in these cases. +and /dev/zero. .SS Btrfs -The swap files on btrfs are supported since Linux 5.0 on files with nocow and -nodatasum attributes and without compression. The previous versions may use -copy-on-write semantic for the swap files, it means that the file location is -may not be static and corruption can result. -.sp -One possible workaround is to map the swap file to a loopback device. This will allow the filesystem -to determine the mapping properly but may come with a performance impact. +Swap files on Btrfs are supported since Linux 5.0 on files with nocow attribute. +See the +.BR btrfs (5) +manual page for more details. .SS NFS Swap over \fBNFS\fR may not work. .SS Suspend @@ -233,6 +231,7 @@ enables libblkid debug output. .BR swapon (2), .BR fstab (5), .BR init (8), +.BR fallocate (1), .BR mkswap (8), .BR mount (8), .BR rc (8) |