[lug] mke2fs

[Nate Duehr]

On Fri, 2002-11-22 at 06:50, Hugh Brown wrote:
> On Thu, 2002-11-21 at 23:10, Prafulla Harpanhalli wrote:
> > depends on how we, as a sysadd, take it. in many cases
> > df -h shows 100% disk utilization on the drive where /
> > is mounted. but, some services, like xfs, run as root
> > & needs some space on the partition.
> > 
> > there are many other similar intricacies involved, i
> > mentioned just one. i had a similar problem which said
> > "could'nt start x font server" & my x used to crash.
> > it took a bit of time to make out the problem. so its
> > better if we leave it the default value.
> > 
> 
> Interesting point.  When mke2fs creates a partition for use, it doesn't
> use all of the available blocks.  e.g.
> 
> Filesystem   1k-blocks    Used   Available Use% Mounted on
> /dev/hdc1    76920416  39533536  35823920  52% /mnt/new
> 
> Usually people discover this by noticing that 1k-blocks - (Used +
> Available) > 0
> 
> 76920416 - (39533536 + 35823920) = 1562960 which is 1.5 gig.
> 
> If I accept the default, the Used + Available is 95% of the 1k-blocks
> and I have 3gigs that root can still use to write to the partition when
> non-root users are told the device is full.
> 
> This is moot since it is not going to be a / partition, but I'm not
> aware of any root process that requires 3gig free in order to start
> (e.g. xfs, and others).  Also, if my / is showing 100%, I have either
> been careless to let if fill up gradually, or there is a runaway process
> that has filled it up and probably filled up the entire partition not
> just the user available portion.
> 
> Hugh
> 
> 
> 
> 
> 
> 
> > HTH
> > 
> > --- "D. Stimits" <stimits at attbi.com> wrote:
> > > Hugh Brown wrote:
> > > 
> > > > I have an 80 gig disk and cringe a little that
> > > 3gig is being reserved
> > > > for use by the super user.
> > > >
> > > > Is there a problem if instead of 5% I set it to
> > > 2%?
> > > >
> > > > What's the downside, if any, of doing this?
> > > >
> > > > Hugh
> > > >
> > > >
> > > I don't personally know of a downside for
> > > that...doesn't mean there 
> > > isn't one...but on a drive that large I suspect 2%
> > > is enough.
> > > 
> > > D. Stimits, stimits AT attbi.com

You could lower the number of blocks reserved for root by using the -m
switch option on mke2fs.  

       −m reserved‐blocks‐percentage
		Specify the percentage of the filesystem blocks
		reserved for the super‐user.  This value defaults to 5%.

There's also -O sparse_super ...

              The following filesystem options are supported:

                   sparse_super
                        Create a filesystem  with  fewer  superblock
			backup copies (saves space on large
			filesystems).


-- 
Nate Duehr, WY0X  (AIM: BigNateCO)
nate at natetech.com