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Old 09-22-2011, 01:38 PM
Camaleón
 
Default regards the /

On Thu, 22 Sep 2011 21:22:12 +0800, lina wrote:

> On Thu, Sep 22, 2011 at 9:13 PM, Camaleón <noelamac@gmail.com> wrote:

(...)

>> >> > after purging, only took
>> >> >
>> >> > # du -sh /lib
>> >> > 128M /lib
>> >> >
>> >> > Thanks for your help. It's done.
>> >>
>> >> Hum... I hope those files are not going to be used anymore by your
>> >> system. By the way, they're not kernels, but "kernel headers",
>> >> mainly
>> >>
>> >>
>> > Read this, I reboot the laptop to test. haha ... seems so far so
>> > good.
>>
>> (...)
>>
>> Good, but you should now what were those folders and what files were
>> storing, most surely kernel symbols but again, they're needed for
>> specific purposes and if you got them installed is because "you"
>> installed by yourself for "something" :-)
>>
>>
> Here is the
>
> :/lib/modules/3.0.0-mbp82-lina$ ls

(...)

But that's not the same as the other folders.

This one contains the modules for that kernel (3.0.0-mbp82-lina) but the
folders you "cleaned" were pointing to kernel headers which now are not
available anymore. I don't tend to compile programs or kernels unless I
have a special need for doing it, so I can't tell what are the drawbacks
the deletion of that folders may have.

Greetings,

--
Camaleón


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Old 09-22-2011, 02:06 PM
Stan Hoeppner
 
Default regards the /

On 9/21/2011 10:43 AM, Camaleón wrote:


...in my case, was
flooding the "/var/log/syslog" file. Then it's too late and your system
may become unstable and slow meaning that you are royaly hosed :-)


Which is why every old school Unix guru (and younger smart ones as well)
will tell you to put /var on a separate filesystem (partition), and
better yet on a separate physical device. The first protects against a
single full filesystem taking the system down. The second does the same
and also makes sure all log related disk bandwidth is on a separate
spindle, thus avoiding the performance degradation when a runaway
process spams the log file with dozens or hundreds of IOs per second.
Note that 7.2k SATA drives can only tackle about 150 IOPS. 5.2k laptop
drives about 100.


Even low end SSD can do 2500 IOPS, 15x that of a 7.2k drive. And most
SSDs are small. So if you have an SSD in this runaway logging scenario
you could potentially fill the log filesystem in a matter of minutes.


Moral of the story: Keep /var/log on a separate filesystem for laptops
and desktops. Keep it on a separate physical device on servers. With a
RAID setup, a separate partition on the LUN/virtual disk serves the same
purpose. Unrelated to this particular problem, but valuable knowledge
nonetheless, is to have a boot partition separate from the / partition
as well.


Ease of use and "Linux on every desktop" proponents evangelize using a
single partition/filesystem, which is the default Microsoft setup BTW,
so it's simpler for the non technical user, though inherently less safe.
Those who have used *nix for a while, especially server
administrators, who have seen problems like this first hand, evangelize
separate partitions/filesystems for reliability, resiliency, and recovery.


The former crowd goes for a "2 hour" afternoon hike in the desert and
takes no supplies, only a digital camera, an iPhone, and a small water
bottle. It's only a 2 hour hike right?


The latter takes a backpack containing a gallon of water, a first aid
kit including anti venom for treating rattlesnake bites, sun block, burn
spray, an MRE, 2 flashlights with spare batteries, a tool kit, a shovel,
a wind proof butane lighter, a pup tent, sleeping bag, blankets, cell
phone and CB radio with extra batteries, and a rain coat.


An hour into his hike, the former takes a rattler bite to the ankle,
falls 20 feet off the rock he's climbing and brakes his right femur.
This particular bite is not by itself life threatening. With no signal
on his iPhone he's unable to call or text for help. He's immobile and
can't walk out. He decides to lie and wait for the next hiker to come
by, not knowing when that will be. He drinks all his meager water
supply, baking in the afternoon sun. A storm rolls in just before night
fall, the temperature dropping to 40F, dropping a short but massive rain
fall. Huddled between the boulders he shivers all night from the wet
and cold, in shorts and a t-shirt. Before dawn he expires due to a
combination of venom, dehydration, hypothermia, and shock.


A month later the latter hikes out and back without issue, in two hours.
Had the former packed and prepared like the latter, he'd be alive
today, at worst maybe with a slight limp.


--
Stan


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Old 09-22-2011, 02:28 PM
Tom H
 
Default regards the /

On Thu, Sep 22, 2011 at 10:06 AM, Stan Hoeppner <stan@hardwarefreak.com> wrote:
>
> Which is why every old school Unix guru (and younger smart ones as well)
> will tell you to put /var on a separate filesystem (partition), and better
> yet on a separate physical device.

To illustrate this point: we have a few boxes (AFAIK, about two dozen)
where, in order to save money, we have "/var" as a directory on "/"
and we regularly have "/" on these boxes filling up because of some
runaway logging to "/var/log"...


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Old 09-22-2011, 02:55 PM
Camaleón
 
Default regards the /

On Thu, 22 Sep 2011 09:06:07 -0500, Stan Hoeppner wrote:

> On 9/21/2011 10:43 AM, Camaleón wrote:
>
>> ...in my case, was
>> flooding the "/var/log/syslog" file. Then it's too late and your system
>> may become unstable and slow meaning that you are royaly hosed :-)
>
> Which is why every old school Unix guru (and younger smart ones as well)
> will tell you to put /var on a separate filesystem (partition), and
> better yet on a separate physical device.

Fair enough with some "buts".

> The first protects against a single full filesystem taking the system
> down.

When you have a hard disk of 8 GiB (and you have installed a full DE plus
1GiB for swap) you have not much room to make such experiments. When disk
space is a constraint, your "/var" partition, whatever it is located, can
be easily flooded in the same way.

The above experience I posted it happened on a VM I have to run testing
for well... "testing" purposes. I wanted to try something (don't remember
exactly what, either "hibernation" or "suspension") and something went
wrong so one of the logs was being flooded with errors. The experiment
(suspension or hibernation) did not succeed and after a hard reset, once
a I logged I received a message popup stating that fact, then issued "df -
h" to check, went to /var/log and saw the big file. I deleted and all
were happy again.

> The second does the same and also makes sure all log related
> disk bandwidth is on a separate spindle, thus avoiding the performance
> degradation when a runaway process spams the log file with dozens or
> hundreds of IOs per second. Note that 7.2k SATA drives can only tackle
> about 150 IOPS. 5.2k laptop drives about 100.

Can you imagine any real performance gain with that setup on a VM machine
that runs over an emulated Pentium M (486, no smp) with 1.5 GiB of RAM
and using a virtual hard disk controller?

That's true for certain environments but it can pass unnoticed on others.

> Even low end SSD can do 2500 IOPS, 15x that of a 7.2k drive. And most
> SSDs are small. So if you have an SSD in this runaway logging scenario
> you could potentially fill the log filesystem in a matter of minutes.
>
> Moral of the story: Keep /var/log on a separate filesystem for laptops
> and desktops. Keep it on a separate physical device on servers. With a
> RAID setup, a separate partition on the LUN/virtual disk serves the same
> purpose. Unrelated to this particular problem, but valuable knowledge
> nonetheless, is to have a boot partition separate from the / partition
> as well.

I'm afraid you ask for too much :-)

> Ease of use and "Linux on every desktop" proponents evangelize using a
> single partition/filesystem, which is the default Microsoft setup BTW,
> so it's simpler for the non technical user, though inherently less safe.

I see disk partitioning as a thing of the past. I would prefer using a
flexible volume manager (such LVM or volume "spanning") although I have
to add an additional layer of complexity. While I agree that 2 TiB for a
single partition is not desiderable for small amounts (<500 GiB) is not
that bad if you take additional precautions (backups, raid and secondary
disks you can use to quickly add more space if needed).

> Those who have used *nix for a while, especially server
> administrators, who have seen problems like this first hand, evangelize
> separate partitions/filesystems for reliability, resiliency, and
> recovery.

(...)

Yes, that's what I've heard and read everywhere (manuals, faqs, technical
books, speciallized sites...), and not only for linux based systems but
also for windows.

Greetings,

--
Camaleón


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Old 09-22-2011, 03:30 PM
lina
 
Default regards the /

On Thu, Sep 22, 2011 at 10:06 PM, Stan Hoeppner <stan@hardwarefreak.com> wrote:

On 9/21/2011 10:43 AM, Camaleón wrote:




...in my case, was

flooding the "/var/log/syslog" file. Then it's too late and your system

may become unstable and slow meaning that you are royaly hosed :-)




Which is why every old school Unix guru (and younger smart ones as well) will tell you to put /var on a separate filesystem (partition), and better yet on a separate physical device. *The first protects against a single full filesystem taking the system down. *The second does the same and also makes sure all log related disk bandwidth is on a separate spindle, thus avoiding the performance degradation when a runaway process spams the log file with dozens or hundreds of IOs per second. Note that 7.2k SATA drives can only tackle about 150 IOPS. *5.2k laptop drives about 100.


There was a geek in our lab long time ago, the partition was inherited from him.
Before I did not understand. Later gradually started to know something, but seems too late.*




Even low end SSD can do 2500 IOPS, 15x that of a 7.2k drive. *And most SSDs are small. *So if you have an SSD in this runaway logging scenario you could potentially fill the log filesystem in a matter of minutes.



Moral of the story: *Keep /var/log on a separate filesystem for laptops and desktops. *Keep it on a separate physical device on servers. *With a RAID setup, a separate partition on the LUN/virtual disk serves the same purpose. *Unrelated to this particular problem, but valuable knowledge nonetheless, is to have a boot partition separate from the / partition as well.

*What's the recommended reserved size for the /var/log partition. I can jotted down and take reference in future.




Ease of use and "Linux on every desktop" proponents evangelize using a single partition/filesystem, which is the default Microsoft setup BTW, so it's simpler for the non technical user, though inherently less safe. *Those who have used *nix for a while, especially server administrators, who have seen problems like this first hand, evangelize separate partitions/filesystems for reliability, resiliency, and recovery.




The former crowd goes for a "2 hour" afternoon hike in the desert and takes no supplies, only a digital camera, an iPhone, and a small water bottle. *It's only a 2 hour hike right?



The latter takes a backpack containing a gallon of water, a first aid kit including anti venom for treating rattlesnake bites, sun block, burn spray, an MRE, 2 flashlights with spare batteries, a tool kit, a shovel, a wind proof butane lighter, a pup tent, sleeping bag, blankets, cell phone and CB radio with extra batteries, and a rain coat.




An hour into his hike, the former takes a rattler bite to the ankle, falls 20 feet off the rock he's climbing and brakes his right femur. This particular bite is not by itself life threatening. *With no signal on his iPhone he's unable to call or text for help. *He's immobile and can't walk out. *He decides to lie and wait for the next hiker to come by, not knowing when that will be. *He drinks all his meager water supply, baking in the afternoon sun. *A storm rolls in just before night fall, the temperature dropping to 40F, dropping a short but massive rain fall. *Huddled between the boulders he shivers all night from the wet and cold, in shorts and a t-shirt. *Before dawn he expires due to a combination of venom, dehydration, hypothermia, and shock.




A month later the latter hikes out and back without issue, in two hours. *Had the former packed and prepared like the latter, he'd be alive today, at worst maybe with a slight limp.

Reading the above three sentences I needed look up dictionaries. Finally got, seems a story, or an analogue.*





--

Stan





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--
Best Regards,

lina
 
Old 09-22-2011, 03:35 PM
lina
 
Default regards the /

On Thu, Sep 22, 2011 at 9:38 PM, Camaleón <noelamac@gmail.com> wrote:

On Thu, 22 Sep 2011 21:22:12 +0800, lina wrote:



> On Thu, Sep 22, 2011 at 9:13 PM, Camaleón <noelamac@gmail.com> wrote:



(...)



>> >> > after purging, only took

>> >> >

>> >> > # du -sh /lib

>> >> > 128M * */lib

>> >> >

>> >> > Thanks for your help. It's done.

>> >>

>> >> Hum... I hope those files are not going to be used anymore by your

>> >> system. By the way, they're not kernels, but "kernel headers",

>> >> mainly

>> >>

>> >>

>> > Read this, I reboot the laptop to test. haha ... seems so far so

>> > good.

>>

>> (...)

>>

>> Good, but you should now what were those folders and what files were

>> storing, most surely kernel symbols but again, they're needed for

>> specific purposes and if you got them installed is because "you"

>> installed by yourself for "something" :-)

>>

>>

> Here is the

>

> :/lib/modules/3.0.0-mbp82-lina$ ls



(...)



But that's not the same as the other folders.



This one contains the modules for that kernel (3.0.0-mbp82-lina) but the

folders you "cleaned" were pointing to kernel headers which now are not

available anymore. I don't tend to compile programs or kernels unless I

have a special need for doing it, so I can't tell what are the drawbacks

the deletion of that folders may have.
Thanks, since there is a free space in /, I will keep it for safe.

.^_^.





Greetings,



--

Camaleón





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--
Best Regards,

lina
 
Old 09-22-2011, 03:45 PM
Tom Furie
 
Default regards the /

On Thu, Sep 22, 2011 at 11:30:05PM +0800, lina wrote:

> What's the recommended reserved size for the /var/log partition. I can
> jotted down and take reference in future.

As with most partitioning schemes, this very much depends on your
requirements. For a desktop/workstation type situation probably 200MB
would be plenty. For a general web/mail/ssh/etc. server as might be run
at home, maybe 500MB would be a better size. In a situation where you
have a central log store with several machines writing their logs there,
you'll need a lot more.

Cheers,
Tom

--
You need tender loving care once a week - so that I can slap you into shape.
-- Ellyn Mustard
 
Old 09-22-2011, 04:02 PM
Camaleón
 
Default regards the /

On Thu, 22 Sep 2011 23:35:44 +0800, lina wrote:

> On Thu, Sep 22, 2011 at 9:38 PM, Camaleón <noelamac@gmail.com> wrote:

(...)

>> >> Good, but you should now what were those folders and what files were
>> >> storing, most surely kernel symbols but again, they're needed for
>> >> specific purposes and if you got them installed is because "you"
>> >> installed by yourself for "something" :-)
>> >>
>> >>
>> > Here is the
>> >
>> > :/lib/modules/3.0.0-mbp82-lina$ ls
>>
>> (...)
>>
>> But that's not the same as the other folders.
>>
>> This one contains the modules for that kernel (3.0.0-mbp82-lina) but
>> the folders you "cleaned" were pointing to kernel headers which now are
>> not available anymore. I don't tend to compile programs or kernels
>> unless I have a special need for doing it, so I can't tell what are the
>> drawbacks the deletion of that folders may have.
>>
> Thanks, since there is a free space in /, I will keep it for safe.
>
> .^_^.

But of course! What I was trying to say is that you should not have
removed the other folders (linux-headers-*) so happily, let alone this
one ;-)

Greetings,

--
Camaleón


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Old 09-22-2011, 04:03 PM
lina
 
Default regards the /

On Thu, Sep 22, 2011 at 11:45 PM, Tom Furie <tom@furie.org.uk> wrote:

On Thu, Sep 22, 2011 at 11:30:05PM +0800, lina wrote:



> What's the recommended reserved size for the /var/log partition. I can

> jotted down and take reference in future.



As with most partitioning schemes, this very much depends on your

requirements. For a desktop/workstation type situation probably 200MB

would be plenty. For a general web/mail/ssh/etc. server as might be run

at home, maybe 500MB would be a better size. In a situation where you

have a central log store with several machines writing their logs there,

you'll need a lot more.

# du -sh /var/log
30M** */var/log

I will take 200MB in future. Thanks.





Cheers,

Tom



--

You need tender loving care once a week - so that I can slap you into shape.

* * * * * * * *-- Ellyn Mustard


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--
Best Regards,

lina
 
Old 09-22-2011, 06:51 PM
green
 
Default regards the /

Tom H wrote at 2011-09-22 09:28 -0500:
> and we regularly have "/" on these boxes filling up because of some
> runaway logging to "/var/log"...

Sounds like the logger (rsyslog?) needs an intelligence upgrade.
 

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