[gentoo-user] Options null for ext4 as root fs

[gentoo-user] Options null for ext4 as root fs

[Mick]

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After multiple fs corruptions and nothing untoward shown by smartctl (I think) 
I decided to move to ext4.

Now when I boot I see a message about my / fs which says Opts: (null)

============================================
dmesg | grep -i EXT4
Command line: root=/dev/sda7 rootfstype=ext4
Kernel command line: root=/dev/sda7 rootfstype=ext4
EXT4-fs (sda7): mounted filesystem with ordered data mode. Opts: (null)
VFS: Mounted root (ext4 filesystem) readonly on device 8:7.
EXT4-fs (sda7): re-mounted. Opts: (null)
EXT4-fs (sda6): mounted filesystem with ordered data mode. Opts: (null)
EXT4-fs (sda8): mounted filesystem with ordered data mode. Opts: (null)
EXT4-fs (sda9): mounted filesystem with ordered data mode. Opts: (null)
EXT4-fs (sda7): re-mounted. Opts: commit=0
EXT4-fs (sda6): re-mounted. Opts: commit=0
EXT4-fs (sda8): re-mounted. Opts: commit=0
EXT4-fs (sda9): re-mounted. Opts: commit=0
EXT4-fs (sda7): re-mounted. Opts: commit=0
EXT4-fs (sda6): re-mounted. Opts: commit=0
EXT4-fs (sda8): re-mounted. Opts: commit=0
EXT4-fs (sda9): re-mounted. Opts: commit=0
============================================

What is the meaning of Opts: (null) ?

All ext4 partitions were created with a number of options; e.g.

Filesystem features:      has_journal ext_attr resize_inode dir_index filetype 
needs_recovery extent flex_bg sparse_super large_file uninit_bg dir_nlink 
extra_isize

but default mount options are shown as:

Default mount options:    (none)

Should I be defining something in fstab?  (currently I only have noatime).
-- 
Regards,
Mick

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Re: [gentoo-user] Options null for ext4 as root fs

[Paul Hartman]

On Tue, Dec 28, 2010 at 7:50 AM, Mick <michaelkintzios@gmail.com> wrote:
> What is the meaning of Opts: (null) ?

My guess is that it is showing the default mount options as stored in
the partition's superblock (set by tune2fs -o xxxxx). You can view the
current default mount options by using "tune2fs -l /dev/sda1" (or
whatever your partition is). Options given on mount commandline (or in
fstab) should override the superblock mount options.

My dmesg shows (null) as yours does, and tune2fs shows me:
Default mount options:    (none)

> All ext4 partitions were created with a number of options; e.g.
>
> Filesystem features:      has_journal ext_attr resize_inode dir_index filetype
> needs_recovery extent flex_bg sparse_super large_file uninit_bg dir_nlink
> extra_isize

Those are characteristics of your filesystem but I don't think they
are considered mount options in this context.

> but default mount options are shown as:
>
> Default mount options:    (none)
>
> Should I be defining something in fstab?  (currently I only have noatime).

You can view the actual mount options currently in use by doing  "cat
/proc/mounts"

In my fstab I have "defaults,noatime" for my rootfs and in
/proc/mounts it shows as:

/dev/root / ext4 rw,noatime,barrier=1,data=ordered 0 0

which looks correct to me.

Re: [gentoo-user] Options null for ext4 as root fs

[Mick]

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On Tuesday 28 December 2010 17:23:22 Paul Hartman wrote:
> On Tue, Dec 28, 2010 at 7:50 AM, Mick <michaelkintzios@gmail.com> wrote:
> > What is the meaning of Opts: (null) ?
> 
> My guess is that it is showing the default mount options as stored in
> the partition's superblock (set by tune2fs -o xxxxx). You can view the
> current default mount options by using "tune2fs -l /dev/sda1" (or
> whatever your partition is). Options given on mount commandline (or in
> fstab) should override the superblock mount options.
> 
> My dmesg shows (null) as yours does, and tune2fs shows me:
> Default mount options:    (none)

OK, same as mine.


> > All ext4 partitions were created with a number of options; e.g.
> > 
> > Filesystem features:      has_journal ext_attr resize_inode dir_index
> > filetype needs_recovery extent flex_bg sparse_super large_file uninit_bg
> > dir_nlink extra_isize
> 
> Those are characteristics of your filesystem but I don't think they
> are considered mount options in this context.

Yes, that's right, but they affect some mount options if the latter are 
explicitly set at fstab.


> You can view the actual mount options currently in use by doing  "cat
> /proc/mounts"
> 
> In my fstab I have "defaults,noatime" for my rootfs and in
> /proc/mounts it shows as:
> 
> /dev/root / ext4 rw,noatime,barrier=1,data=ordered 0 0
> 
> which looks correct to me.


Same here:

/dev/root / ext4 rw,noatime,barrier=1,data=ordered 0 0

Is that all that is required for ext4?  Do we need to define anything else to 
take advantage of the various ext4 options (see below)?

http://www.mjmwired.net/kernel/Documentation/filesystems/ext4.txt#125
-- 
Regards,
Mick

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