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carpman
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PostPosted: Tue Feb 12, 2008 11:01 am    Post subject: sym linking /tmp Reply with quote

Hello, on new install was thinking of doing away with /tmp partition and just sym linking it to a /var/tmp partition are there are issues with doing this or can i just do and not worry?

cheers
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i92guboj
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PostPosted: Tue Feb 12, 2008 11:35 am    Post subject: Re: sym linking /tmp Reply with quote

carpman wrote:
Hello, on new install was thinking of doing away with /tmp partition and just sym linking it to a /var/tmp partition are there are issues with doing this or can i just do and not worry?

cheers


I usually do this on my desktop machine and haven't had any problem for years.
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schachti
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PostPosted: Tue Feb 12, 2008 5:08 pm    Post subject: Reply with quote

Instead of symlinking, you can do it using mount:

Code:
mount -bind /var/tmp /tmp

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i92guboj
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PostPosted: Tue Feb 12, 2008 5:23 pm    Post subject: Reply with quote

Actually, what I do is to just mount the same device at two points from fstab.

But any solution should work the same as far as I can tell.

Code:

$ grep tmp /etc/fstab
none /dev/shm   tmpfs nodev,nosuid,noexec 0 0
/dev/sdc9 /tmp ext2 noatime 0 1
/dev/sdc9 /var/tmp ext2 noatime 0 1
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nixnut
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PostPosted: Tue Feb 12, 2008 7:20 pm    Post subject: Reply with quote

Moved from Installing Gentoo to Other Things Gentoo.
Not about getting gentoo installed, so moved here,
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carpman
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PostPosted: Tue Feb 12, 2008 8:13 pm    Post subject: Reply with quote

i92guboj wrote:
Actually, what I do is to just mount the same device at two points from fstab.

But any solution should work the same as far as I can tell.

Code:

$ grep tmp /etc/fstab
none /dev/shm   tmpfs nodev,nosuid,noexec 0 0
/dev/sdc9 /tmp ext2 noatime 0 1
/dev/sdc9 /var/tmp ext2 noatime 0 1



did not know that was possible?
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i92guboj
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PostPosted: Tue Feb 12, 2008 8:18 pm    Post subject: Reply with quote

carpman wrote:
i92guboj wrote:
Actually, what I do is to just mount the same device at two points from fstab.

But any solution should work the same as far as I can tell.

Code:

$ grep tmp /etc/fstab
none /dev/shm   tmpfs nodev,nosuid,noexec 0 0
/dev/sdc9 /tmp ext2 noatime 0 1
/dev/sdc9 /var/tmp ext2 noatime 0 1



did not know that was possible?


That's the way I do it, and it certainly worked for a few years now.

Code:

# mount | grep tmp
udev on /dev type tmpfs (rw,nosuid)
none on /dev/shm type tmpfs (rw,noexec,nosuid,nodev)
/dev/sdc9 on /tmp type ext2 (rw,noatime)
/dev/sdc9 on /var/tmp type ext2 (rw,noatime)
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mv
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PostPosted: Tue Feb 12, 2008 8:30 pm    Post subject: Reply with quote

i92guboj wrote:
Code:
/dev/sdc9 /tmp ext2 noatime 0 1
/dev/sdc9 /var/tmp ext2 noatime 0 1

I don't remember where I read it, but this was explicitly discouraged in some official document, because you have no guarantee that the kernel recognizes that this is the same filesystem just mounted twice. It is more secure to tell him explicitly, using --bind:
Code:
/dev/sdc9 /tmp ext2 noatime 0 1
/tmp /var/tmp none bind 0 0
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i92guboj
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PostPosted: Tue Feb 12, 2008 8:38 pm    Post subject: Reply with quote

mv wrote:
i92guboj wrote:
Code:
/dev/sdc9 /tmp ext2 noatime 0 1
/dev/sdc9 /var/tmp ext2 noatime 0 1

I don't remember where I read it, but this was explicitly discouraged in some official document, because you have no guarantee that the kernel recognizes that this is the same filesystem just mounted twice. It is more secure to tell him explicitly, using --bind:
Code:
/dev/sdc9 /tmp ext2 noatime 0 1
/tmp /var/tmp none bind 0 0


It worked here for many years, but that doesn't mean it is correct.

Do you remember something more or can you give me any clue on what to search for so I can research a bit more on this?
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mv
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PostPosted: Tue Feb 12, 2008 10:27 pm    Post subject: Reply with quote

i92guboj wrote:
Do you remember something more

No, sorry. It was many years ago that I read this. Maybe for current kernels it is not even true anymore.
On the other hand, it might happen that you have no problems for a long time but there can be race conditions anyway: It is not hard to imagine problematic situations which might happen if one of the mounts has just cached a block which the other changes...

Actually, I used to mount the same FAT partition twice with different options. But I would not dare to write on both simultaneously...
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i92guboj
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PostPosted: Tue Feb 12, 2008 10:42 pm    Post subject: Reply with quote

mv wrote:
i92guboj wrote:
Do you remember something more

No, sorry. It was many years ago that I read this. Maybe for current kernels it is not even true anymore.
On the other hand, it might happen that you have no problems for a long time but there can be race conditions anyway: It is not hard to imagine problematic situations which might happen if one of the mounts has just cached a block which the other changes...

Actually, I used to mount the same FAT partition twice with different options. But I would not dare to write on both simultaneously...


Yes, race conditions is what I had in mind. But the fact is that, well, both are tmp partitions. And in gentoo you can spend literally hours or days compiling and writing thousands or even hundreds of thousands of files into /var/tmp/portage, while you use /tmp (which is on the same partition) to store the users temporal stuff.

So, it would be the best environment to reproduce such a race condition, and for years and years of Gentoo, I haven't noticed any kind of corruption at all.

Anyway, there is nothing valuable on this partition, and the contents is erased on bootup anyway, so, that might be it as well...
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