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aclparameter enables access control lists, while the
user_xattrparameter enables user extended attributes. To enable both options, use their respective parameters with
-o, as in:
mount -o acl,user_xattr /dev/
tune2fsutility allows administrators to set default mount options in the file system superblock. For more information on this, refer to
By default, ext4 uses write barriers to ensure file system integrity even when power is lost to a
device with write caches enabled. For devices without write caches, or with battery-backed write caches,
disable barriers using the
nobarrier option, as in:
mount -o nobarrier /dev/
For more information about write barriers, refer to Chapter 16, Write Barriers.
Pervasive Code » Recommended mount options for ext3
if you disable
atime updates, using the
noatime mount option you can get
a performance boost.
This is done by adding
noatime to the appropriate lines in
it once for each ext3 filesystem that’s listed), in the fourth column, which probably says
To make this change to a live, running filesystem, remount the drive (adjust this so that the right disk device is specified at the end of the line:
sudo mount -o noatime,nodiratime,remount,rw /dev/xvda1
(My understanding is that the
noatime implies the
nodiratime option, but
I decided to add it just in case this was not true.)
atime is a relative of the well known file modification and creation timestamps, but
it tracks access to file data. That means that if you read one byte from a file, even if it’s cached
in RAM, you’re actually also triggering a write to the directory entry for that file, so that its
atime can be updated. (If you want to slap your forehead now in disbelief, be my guest.)
And if you read a ton of little files (which happens rather often in the unix world), that means
a ton of writes to update all of their directory entries. You don’t want that, right?
But do you need it? Almost certainly not. It’s required by the POSIX standard, and the need for it to be present and turned on is well debated by people more knowledgeable about this in this thread from the Linux kernel mailing list. The summary of their argument is that it’s the kernel’s job to remain standards compliant, and only the distributor or user has enough information to know that they don’t care about that part of the standard and can safely disable it. I can understand that point of view.
Well, I did the reading, and you can safely disable it, unless you’re using mutt. If you’re using
mutt, or if you’re just nervous about disabling something that somebody somewhere says you might maybe
need someday, then disable
atime for every filesystem that doesn’t have your mail spool
on it, and use the
relatime mode on that drive. (
relatime is a clever hack
atime behavior while skipping the disk write in certain cases.)
You can turn it dynamically using remount: Attempt to remount an already-mounted file system. This
is commonly used to change the mount flags for a file system, especially to make a readonly file system
writeable. It does not change device or mount point.
auto -- The filesystem can be mounted automatically (at bootup, or when mount is used with the -a option). This is really unnecessary as this is the default action of mount -a anyway.
mount(8) mount a file system - Linux man page
There are a number of interesting options which can be included using the -o parameter. While these are probably most useful in the context of /etc/fstab (see later), there are occasions where it may be helpful to be aware of them.
-etc-fstab under Linux
As the filesystems in /etc/fstab will eventually be mounted using mount(8) it isn't surprising that the options field simply contains a comma-seperated list of options which will be passed directly to mount when it tries to mount the filesystem.
The options common to all filesystems are:
Mount options to improve ext4 file system performance
Web Development Advice and Tips
I recently boosted my rails test suite running time by around 30% by adding certain mount options for my ext4 partition (works for ext3 too). I thought I’d blog about it because the first time I tried my system wouldn’t boot! So here are the step by step instructions:
> tune2fs -o journal_data_writeback /dev/sdXY
Where /dev/sdXY is replaced by the partition that you want to boost
4) Edit fstab
> nano -w /mnt/sdXY/etc/fstab
Find the line that references sdXY. It will look something like:
UUID=be2f0ac2-4683-4550-bcd1-704a1a840b3e / ext4 relatime,errors=remount-ro 0 1
The first entry is the UUID (although on your system this could just be /dev/sdXY). The second entry is the path (/ for me). Third is the fstype (ext3/4). Fourth are the options. Fifth is for dump and sixth is pass. See man fstab(5) for more info.
Change the options to:
(you can leave all of yours in place, if they weren’t the same as mine.
The main ones are replacing atime/relatime with noatime. This causes the FS to not write read-times to a file when read. Think about it. Writing to the FS for every read of the FS? crazy!
Next is data=writeback. This means that metadata for files can be written lazily after the file is written. This will not cause file system corruption, but it may cause the most recent changes to be lost in the event of a crash (so you may jump back into the past a bit).
Next is barrier, which is slightly more dangerous:
barrier=<0|1(*)> This enables/disables the use of write barriers in
the jbd code. barrier=0 disables, barrier=1 enables.
This also requires an IO stack which can support
barriers, and if jbd gets an error on a barrier
write, it will disable again with a warning.
Write barriers enforce proper on-disk ordering
of journal commits, making volatile disk write caches
safe to use, at some performance penalty. If
your disks are battery-backed in one way or another,
disabling barriers may safely improve performance.
Next is nobh:
bh (*) ext4 associates buffer heads to data pages to
nobh (a) cache disk block mapping information
(b) link pages into transaction to provide
“bh” option forces use of buffer heads.
“nobh” option tries to avoid associating buffer
heads (supported only for “writeback” mode).
You can skip barrier and nobh if you’d like. noatime and data=writeback are the big ones.
6) Reboot to your system.
If you have any trouble booting, just boot a recovery disk and revert the fstab changes.
EDIT: Updated to no longer require recovery disk booting thanks to Nicolas Alpi’s response post.
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