Hi ,

  We need to migrate one of the applications from FreeBSD to Linux .
But need some clarification before we go
  ahead with the migration.

 Under these FreeBSD hosts , the /tmp partition is created under /home
and a symbolic link is created to /tmp

-bash-3.2$ ls -ld /tmp
lrwxrwxrwx  1 root  root  8 Feb 24  2009 /tmp -> home/tmp

But our existing Linux hosts are having the following  layout for /
tmp .

df -lh /tmp/
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/sys-tmp   3.9G   46M  3.7G   2% /tmp

df -lh /tmp/
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             9.7G  2.2G  7.0G  25% /

Some of the linux hosts are having separate partition for /tmp and
some are under / .

Our applications are failing because of the different layout for /tmp
in Linux . One solution we have thought of moving the /tmp partition
to /home and then create a
symbolic link from /home/tmp to /tmp . The original /tmp which is a
separate partition will be renamed to some /temp.

grep tmp /etc/fstab

/dev/sys/tmp         /tmp                 ext3     defaults     0 0

will be changed to something like this.

/dev/sys/temp         /temp                 ext3     defaults     0 0

-bash-3.2$ ls -ld /tmp
lrwxrwxrwx  1 root  root  8 Feb 24  2009 /tmp -> home/tmp

Our worry is whether will there be any effect in the normal
functioning of the OS . Will there be any impact on the Linux
applications which are already running are using /tmp for some use.

Should not have any
effect as far as I understand as we are creating a symbolic link from /
home/tmp to /tmp. As it is Prod host , we want to be sure before going
ahead with the migration without having any impact on the host and
applications already running . Please give your views.

With Thanks in Advance
--Zaman

-bash-3.2$ ls -ld /tmp
lrwxrwxrwx 1 root root 8 Feb 24 2009 /tmp -> home/tmp

df -lh /tmp/
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/sys-tmp   3.9G   46M  3.7G   2% /tmp

We need to migrate one of the applications from FreeBSD to Linux .

But need some clarification before we go ahead with the migration.

Under these FreeBSD hosts , the /tmp partition is created under /home
and a symbolic link is created to /tmp

-bash-3.2$ ls -ld /tmp
lrwxrwxrwx 1 root root 8 Feb 24 2009 /tmp -> home/tmp

But our existing Linux hosts are having the following layout for /
tmp .

df -lh /tmp
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/sys-tmp 3.9G 46M 3.7G 2% /tmp

df -lh /tmp
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 9.7G 2.2G 7.0G 25% /

Some of the linux hosts are having separate partition for /tmp and
some are under / .

Our applications are failing because of the different layout for /tmp
in Linux .

One solution we have thought of moving the /tmp partition to /home and
then create a symbolic link from /home/tmp to /tmp . The original /tmp
which is a separate partition will be renamed to some /temp.

grep tmp /etc/fstab

/dev/sys/tmp /tmp ext3 defaults 0 0

will be changed to something like this.

/dev/sys/temp /temp ext3 defaults 0 0

-bash-3.2$ ls -ld /tmp
lrwxrwxrwx 1 root root 8 Feb 24 2009 /tmp -> home/tmp

Our worry is whether will there be any effect in the normal
functioning of the OS .

Will there be any impact on the Linux applications which are already
running are using /tmp for some use.

Should not have any effect as far as I understand as we are creating a
symbolic link from /home/tmp to /tmp.

As it is Prod host , we want to be sure before going ahead with the
migration without having any impact on the host and applications
already running . Please give your views.

On Tuesday 15 September 2009 09:22, someone identifying as *bzaman*
wrote in /comp.os.linux.setup:/

-bash-3.2$ ls -ld /tmp
lrwxrwxrwx 1 root root 8 Feb 24 2009 /tmp -> home/tmp

Like I said, this is the wrong way to do it. Whoever set up the
system like that is probably an ex-Windows user, and thus accustomed
to a single-user set up.

Our applications are failing because of the different layout
for /tmp in Linux.

On Sep 15, 3:22 am, bzaman <bzaman.las... at (no spam) gmail.com> wrote:

lrwxrwxrwx  1 root  root  8 Feb 24  2009 /tmp -> home/tmp

This sort of "hide the diskspace" game is common. I do hope that
your backup system knows to ignore /home/tmp? And that looks
broken: shouldn't the link be to /home/tmp?

Well, I know of some people who have */tmp* being a symlink
to */var/tmp,* yes - in a way, it makes sense,

On Tuesday 15 September 2009 09:22, someone identifying as *bzaman*
wrote in /comp.os.linux.setup:/

We need to migrate one of the applications from FreeBSD to Linux .

Okay... :-)

But need some clarification before we go ahead with the migration.

Under these FreeBSD hosts , the /tmp partition is created under /home
and a symbolic link is created to /tmp

That's peculiar, because that would be the entirely opposite approach of
the multi-user philosophy.  Normally, */tmp* in the root directory -
note: I am not saying "in the root filesystem" but "in the root
directory" - would be the actual storage for temporary files such as
sockets and the likes, and the user's home directory would or could
then possibly contain a symlink to the /real/ */tmp.*

-bash-3.2$ ls -ld /tmp
lrwxrwxrwx  1 root  root  8 Feb 24  2009 /tmp -> home/tmp

Like I said, this is the wrong way to do it.  Whoever set up the system
like that is probably an ex-Windows user, and thus accustomed to a
single-user set up.

But our existing Linux hosts are having the following  layout for /
tmp .

df -lh /tmp
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/sys-tmp   3.9G   46M  3.7G   2% /tmp

(Note: trailing slash removed in the quoted command for newsreader text
formatting reasons.  Likewise for the following quoted command.)

Okay, so on this system */tmp* is on a logical volume.  Not my preferred
choice, but good enough.

df -lh /tmp
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             9.7G  2.2G  7.0G  25% /

Okay, this is already better than how it was done on the FreeBSD
machine, but not quite a professional approach either.  The idea is to
keep the root filesystem as static as possible, so you should
definitely split off the contents of */tmp* - and for that matter,
*/var* and */home* - from the root filesystem, especially for a server.

According to the File Hierarchy Standard (FHS) version 2.3, nothing
residing in */tmp* should be required to survive a reboot, and
therefore my favored and recommended approach is to have the contents
of */tmp* reside on a /tmpfs/ of limited size.

Some of the linux hosts are having separate partition for /tmp and
some are under / .

Uhuh, but see the last of the two above paragraphs. ;-)

Our applications are failing because of the different layout for /tmp
in Linux .

That is most likely due to a permissions problem.  The */tmp* directory
in the root directory must have 1777 permissions, i.e. read, write and
execute/traverse permission for everyone, and with the sticky bit set.
The permissions mask for */tmp* should be "trwxrwxrwx".

By making the */tmp* in the root directory a symlink to a user-owned
directory, you are effectively disabling the required permissions on
*/tmp* for stuff that is not explicitly started by root or by the user
in whose home directory the mountpoint to the actual temporary
filesystem resides.  Presumably, the person who set it up that way has
messed around with SUID bits and/or the permissions on the pertainining
user account's home directory.

One solution we have thought of moving the /tmp partition to /home and
then create a symbolic link from /home/tmp to /tmp . The original /tmp
which is a separate partition will be renamed to some /temp.

That is the totally wrong approach.  You would be duplicating the
FreeBSD set-up - of which I cannot imagine that FreeBSD itself would
actually force such a policy upon the user, since it is totally
perverse to the UNIX philosophy - but you would then only be treating
the symptoms, not the cause.

grep tmp /etc/fstab

/dev/sys/tmp         /tmp                 ext3     defaults     0 0

will be changed to something like this.

/dev/sys/temp         /temp                 ext3     defaults     0 0

No, definitely not the right approach.

-bash-3.2$ ls -ld /tmp
lrwxrwxrwx  1 root  root  8 Feb 24  2009 /tmp -> home/tmp

Absolutely the wrong way.

Our worry is whether will there be any effect in the normal
functioning of the OS .

Yes, because */home/tmp* - or */home/$LOGIN/tmp* for that matter - won't
be world-writeable or sticky.

Will there be any impact on the Linux applications which are already
running are using /tmp for some use.

I'm not sure /what/ the impact will be, considering that I have
insufficient information regarding what is being executed on the
machine and by whom - i.e. under which user accounts.  But yes, most
likely messing around with things like that would screw up the
functioning of the system.

Should not have any effect as far as I understand as we are creating a
symbolic link from /home/tmp to /tmp.

Of course it will have effects, because */tmp* requires special
permissions - see higher up - and you cannot give it those under
*/home* without compromising system integrity and security.

As it is Prod host , we want to be sure before going ahead with the
migration without having any impact on the host and applications
already running . Please give your views.

If this is a production machine - i.e. a server - then the whole precept
of using a temporary filesystem (or mountpoint) under */home* is
definitely wrong to begin with.

Hope this helps...

--
*Aragorn*
(registered GNU/Linux user #223157)