[gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[gottlieb]

I use lvm and use it for /var.
In fstab I have
  /dev/vg/var  /mnt/var  ext4  defaults  0 2
I also have
  lrwxrwxrwx 1 root root 7 Aug 31 16:13 /var -> mnt/var

(Similar setup for /tmp and /opt)

This has worked ok but revdep-rebuild is not happy

root@E6510 cache # revdep-rebuild
 * Configuring search environment for revdep-rebuild
 * Working directory expected to be /var/cache/revdep-rebuild, but it is /mnt/var/cache/revdep-rebuild
root@E6510 cache #

I don't intend to fight revdep-rebuild so will change and mount directly
onto /var, but I wonder what is the concern.

Should I also mount directly onto /tmp and /opt?

thanks,
allan

Re: [gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[Canek Peláez Valdés]

On Mon, Sep 9, 2013 at 1:51 PM,  <gottlieb@nyu.edu> wrote:
> I use lvm and use it for /var.
> In fstab I have
>   /dev/vg/var  /mnt/var  ext4  defaults  0 2
> I also have
>   lrwxrwxrwx 1 root root 7 Aug 31 16:13 /var -> mnt/var
>
> (Similar setup for /tmp and /opt)
>
> This has worked ok but revdep-rebuild is not happy
>
> root@E6510 cache # revdep-rebuild
>  * Configuring search environment for revdep-rebuild
>  * Working directory expected to be /var/cache/revdep-rebuild, but it is /mnt/var/cache/revdep-rebuild
> root@E6510 cache #
>
> I don't intend to fight revdep-rebuild so will change and mount directly
> onto /var, but I wonder what is the concern.

I think it's the symlink the thing that is making revdep-rebuild
unhappy. Have you tried to bind mount /mnt/var into /var?

mount -o bind /mnt/var /var

Perhaps that will appease revdep-rebuild.

> Should I also mount directly onto /tmp and /opt?

I don't think so, although /tmp is preferred to be a tmpfs now, I
believe (in both systemd and OpenRC, if I'm not mistaken).

Regards.
-- 
Canek Peláez Valdés
Posgrado en Ciencia e Ingeniería de la Computación
Universidad Nacional Autónoma de México

Re: [gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[gottlieb]

On Mon, Sep 09 2013, Canek Peláez Valdés wrote:

> On Mon, Sep 9, 2013 at 1:51 PM,  <gottlieb@nyu.edu> wrote:
>> In fstab I have
>>   /dev/vg/var  /mnt/var  ext4  defaults  0 2
>> I also have
>>   lrwxrwxrwx 1 root root 7 Aug 31 16:13 /var -> mnt/var
>>
>> This has worked ok but revdep-rebuild is not happy
>
> I think it's the symlink the thing that is making revdep-rebuild
> unhappy. Have you tried to bind mount /mnt/var into /var?
>
> mount -o bind /mnt/var /var

Works great.  Thanks.  To make it permanent I put
    /mnt/var     /var      ext4     bind       0 0
right under
    /dev/vg/var  /mnt/var  ext4     defaults   0 2
in /etc/fstab

>> Should I also mount directly onto /tmp and /opt?
>
> I don't think so, although /tmp is preferred to be a tmpfs now, I
> believe (in both systemd and OpenRC, if I'm not mistaken).

To use tmpfs I will first have to teach myself not to put things in /tmp
that I expect to need for only a few days (I have wipe_tmp="NO"; and use
30 days for tmpwatch).

thanks again,
allan

Re: [gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[Alan McKinnon]

On 10/09/2013 00:26, gottlieb@nyu.edu wrote:
> On Mon, Sep 09 2013, Canek Peláez Valdés wrote:
> 
>> On Mon, Sep 9, 2013 at 1:51 PM,  <gottlieb@nyu.edu> wrote:
>>> In fstab I have
>>>   /dev/vg/var  /mnt/var  ext4  defaults  0 2
>>> I also have
>>>   lrwxrwxrwx 1 root root 7 Aug 31 16:13 /var -> mnt/var
>>>
>>> This has worked ok but revdep-rebuild is not happy
>>
>> I think it's the symlink the thing that is making revdep-rebuild
>> unhappy. Have you tried to bind mount /mnt/var into /var?
>>
>> mount -o bind /mnt/var /var
> 
> Works great.  Thanks.  To make it permanent I put
>     /mnt/var     /var      ext4     bind       0 0
> right under
>     /dev/vg/var  /mnt/var  ext4     defaults   0 2
> in /etc/fstab

I'm curious as to why you do that, I can't see any benefit at all.

The "var" filesystem is an LV and is only useful if it is mounted at
/var where packages expect it to be. Why add the extra complexity  of
mounting it somewhere else and then bind mounting it to the pnly place
it can be useful?

If you really want a bind mount (to for example work with only that
filesystem's objects and not have to deal with submounts below /var),
why not just mount the LV directly at /var and bind mount it to /mnt/var?

I'm assuming you do this for backup purposes or similar - some really
dumb backup software out there can't detect when it crosses a mount
point (I know this because I've had to deal with idiots who purchase
such software and have the power to insist I use it...)

If so, why not have your backup script mount the fs in /mnt, and umount
it when done?

> 
>>> Should I also mount directly onto /tmp and /opt?
>>
>> I don't think so, although /tmp is preferred to be a tmpfs now, I
>> believe (in both systemd and OpenRC, if I'm not mistaken).
> 
> To use tmpfs I will first have to teach myself not to put things in /tmp
> that I expect to need for only a few days (I have wipe_tmp="NO"; and use
> 30 days for tmpwatch).

There's rules of thumb about this that will always work:

No object in /tmp can be expected to survive successive invocations of
the program that created the object, and never survive a reboot;
No object in /var/tmp can be expected to survive a reboot

The best place for temp files, ironically, is ~



-- 
Alan McKinnon
alan.mckinnon@gmail.com

Re: [gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[gottlieb]

On Mon, Sep 09 2013, Alan McKinnon wrote:

> On 10/09/2013 00:26, gottlieb@nyu.edu wrote:
>> On Mon, Sep 09 2013, Canek Peláez Valdés wrote:
>> 
>>> On Mon, Sep 9, 2013 at 1:51 PM,  <gottlieb@nyu.edu> wrote:
>>>> In fstab I have
>>>>   /dev/vg/var  /mnt/var  ext4  defaults  0 2
>>>> I also have
>>>>   lrwxrwxrwx 1 root root 7 Aug 31 16:13 /var -> mnt/var
>>>>
>>>> This has worked ok but revdep-rebuild is not happy
>>>
>>> I think it's the symlink the thing that is making revdep-rebuild
>>> unhappy. Have you tried to bind mount /mnt/var into /var?
>>>
>>> mount -o bind /mnt/var /var
>> 
>> Works great.  Thanks.  To make it permanent I put
>>     /mnt/var     /var      ext4     bind       0 0
>> right under
>>     /dev/vg/var  /mnt/var  ext4     defaults   0 2
>> in /etc/fstab
>
> I'm curious as to why you do that, I can't see any benefit at all.
>
> The "var" filesystem is an LV and is only useful if it is mounted at
> /var where packages expect it to be. Why add the extra complexity  of
> mounting it somewhere else and then bind mounting it to the pnly place
> it can be useful?

An old habit/belief that mounts go in /mnt.  Since both revdep-rebuild
and you believe this is a bad habit, I now mount directly on /var /opt.

> There's rules of thumb about this that will always work:
>
> No object in /tmp can be expected to survive successive invocations of
> the program that created the object, and never survive a reboot;
> No object in /var/tmp can be expected to survive a reboot
>
> The best place for temp files, ironically, is ~

I set tmpwatch and wipe_tmp so that files survive in /tmp and /var/tmp
for a month.

I don't like ~ for temp files since on some, admittedly rare, occasions
I actually use the gnome gui file manager and don't want a huge ~.  I
have long ago created ~/tmp (also cleaned after a month by tmpwatch) so
the only problem is breaking the habit of placing short-term files in
/tmp instead of ~/tmp.

I realize that habit is bad for my (system's) health, but still find it
hard to break.  I shall try again. Perhaps this is very mild form of
what intelligent smokers feel :-).

allan

Re: [gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[Alan McKinnon]

On 10/09/2013 18:57, gottlieb@nyu.edu wrote:
>> I'm curious as to why you do that, I can't see any benefit at all.
>> >
>> > The "var" filesystem is an LV and is only useful if it is mounted at
>> > /var where packages expect it to be. Why add the extra complexity  of
>> > mounting it somewhere else and then bind mounting it to the pnly place
>> > it can be useful?
> An old habit/belief that mounts go in /mnt.  Since both revdep-rebuild
> and you believe this is a bad habit, I now mount directly on /var /opt.

Ah, OK.

Technically a mount can go anywhere. Permanent mounts just go where they
are supposed to go, and /mnt was a throwback to the bad old days where
everything else was mounted at /mnt/<something>, including cdroms,
filesystems you wanted to access quickly, windows partitions on a dual
boot machine etc etc. or the gentoo partition during install before your
chroot

Then removeable media started being mounted in /media where the GUI
could manage it and not have to deal with root-only permissions in /mnt

Nowadays media goes in /run/media....

All very confusing and hard to keep up with. It's like trying to figure
out what politicians and your boss happen to be talking about today :-)



> 
>> > There's rules of thumb about this that will always work:
>> >
>> > No object in /tmp can be expected to survive successive invocations of
>> > the program that created the object, and never survive a reboot;
>> > No object in /var/tmp can be expected to survive a reboot
>> >
>> > The best place for temp files, ironically, is ~
> I set tmpwatch and wipe_tmp so that files survive in /tmp and /var/tmp
> for a month.
> 
> I don't like ~ for temp files since on some, admittedly rare, occasions
> I actually use the gnome gui file manager and don't want a huge ~.  I
> have long ago created ~/tmp (also cleaned after a month by tmpwatch) so
> the only problem is breaking the habit of placing short-term files in
> /tmp instead of ~/tmp.

OK, I get it. I'd write all that temp stuff to /var/tmp so it doesn't
get nuked by something cleverly trying to manage /tmp.

I often feel the same way about ~/.xsession-errors.
I have to restrain myself from symlinking it to /dev/null :-)

> I realize that habit is bad for my (system's) health, but still find it
> hard to break.  I shall try again. Perhaps this is very mild form of
> what intelligent smokers feel :-).

There is no such thing as an intelligent smoker; there are only stupid
smokers :-)

I'm a two-packs-a-day man myself, I speak from many years experience!


-- 
Alan McKinnon
alan.mckinnon@gmail.com

Re: [gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[gottlieb]

On Tue, Sep 10 2013, Alan McKinnon wrote:

> On 10/09/2013 18:57, gottlieb@nyu.edu wrote:
>
>> Alan McKinnon wrote:

>>> > There's rules of thumb about this that will always work:
>>> >
>>> > No object in /tmp can be expected to survive successive invocations of
>>> > the program that created the object, and never survive a reboot;
>>> > No object in /var/tmp can be expected to survive a reboot
>>> >
>>> > The best place for temp files, ironically, is ~
>> I set tmpwatch and wipe_tmp so that files survive in /tmp and /var/tmp
>> for a month.
>> 
>> I don't like ~ for temp files since on some, admittedly rare, occasions
>> I actually use the gnome gui file manager and don't want a huge ~.  I
>> have long ago created ~/tmp (also cleaned after a month by tmpwatch) so
>> the only problem is breaking the habit of placing short-term files in
>> /tmp instead of ~/tmp.
>
> OK, I get it. I'd write all that temp stuff to /var/tmp so it doesn't
> get nuked by something cleverly trying to manage /tmp.

But A. McKinnon says (above) that an always valid rule of thumb is
"No object in /var/tmp can be expected to survive a reboot".

>> I realize that habit is bad for my (system's) health, but still find it
>> hard to break.  I shall try again. Perhaps this is very mild form of
>> what intelligent smokers feel :-).
>
> There is no such thing as an intelligent smoker; there are only stupid
> smokers :-)
>
> I'm a two-packs-a-day man myself, I speak from many years experience!

I promise not to mention it again, but you really should quit.

I consider one of my contributions to computer architecture is being at
least a little influential in getting Per Stenstrom to quit.  At the
time he was a rising star, who I felt would contribute greatly if he
didn't get sick from the cigs.  He did quit and has certainly
contributed.

allan

Re: [gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[Alan McKinnon]

On 11/09/2013 04:02, gottlieb@nyu.edu wrote:
> On Tue, Sep 10 2013, Alan McKinnon wrote:
> 
>> On 10/09/2013 18:57, gottlieb@nyu.edu wrote:
>>
>>> Alan McKinnon wrote:
> 
>>>>> There's rules of thumb about this that will always work:
>>>>>
>>>>> No object in /tmp can be expected to survive successive invocations of
>>>>> the program that created the object, and never survive a reboot;
>>>>> No object in /var/tmp can be expected to survive a reboot
>>>>>
>>>>> The best place for temp files, ironically, is ~
>>> I set tmpwatch and wipe_tmp so that files survive in /tmp and /var/tmp
>>> for a month.
>>>
>>> I don't like ~ for temp files since on some, admittedly rare, occasions
>>> I actually use the gnome gui file manager and don't want a huge ~.  I
>>> have long ago created ~/tmp (also cleaned after a month by tmpwatch) so
>>> the only problem is breaking the habit of placing short-term files in
>>> /tmp instead of ~/tmp.
>>
>> OK, I get it. I'd write all that temp stuff to /var/tmp so it doesn't
>> get nuked by something cleverly trying to manage /tmp.
> 
> But A. McKinnon says (above) that an always valid rule of thumb is
> "No object in /var/tmp can be expected to survive a reboot".


There's another rule of thumb that's even more applicable:

"We always do it this way, except when we don't"

I use this to great effect all the time, usually when I'm determined to
get my own way at work. I highly recommend this approach, when used with
a good healthy dose of intelligence you can get awesome things done :-)


> 
>>> I realize that habit is bad for my (system's) health, but still find it
>>> hard to break.  I shall try again. Perhaps this is very mild form of
>>> what intelligent smokers feel :-).
>>
>> There is no such thing as an intelligent smoker; there are only stupid
>> smokers :-)
>>
>> I'm a two-packs-a-day man myself, I speak from many years experience!
> 
> I promise not to mention it again, but you really should quit.
> 
> I consider one of my contributions to computer architecture is being at
> least a little influential in getting Per Stenstrom to quit.  At the
> time he was a rising star, who I felt would contribute greatly if he
> didn't get sick from the cigs.  He did quit and has certainly
> contributed.

You are correct of course, and I have no sensible answer for that :-)

The one answer I do have is "see earlier comment 8 paragraphs above"




-- 
Alan McKinnon
alan.mckinnon@gmail.com

Re: [gentoo-user] why does revdep-rebuild object to mounting /var on /mnt/var ?

[gottlieb]

On Wed, Sep 11 2013, Alan McKinnon wrote:

>>> OK, I get it. I'd write all that temp stuff to /var/tmp so it doesn't
>>> get nuked by something cleverly trying to manage /tmp.
>> 
>> But A. McKinnon says (above) that an always valid rule of thumb is
>> "No object in /var/tmp can be expected to survive a reboot".
>
> There's another rule of thumb that's even more applicable:
>
> "We always do it this way, except when we don't"
>
Now I understand.  Amazing what you learn from this group.
allan