How do I limit I/O usage for a user/process? A user broke my system

Steve O'Hara-Smith steve at
Fri Aug 19 09:57:37 UTC 2016

On Fri, 19 Aug 2016 09:23:16 +0000
Magnus Ahriman <magnus.ahriman at> wrote:

> Hi,
> Today I had a user who decided to open a very large text file in pico. The
> result was a complete denial of service of the system and everything
> stalled/was working veeeeery slowly.

	How much memory have you got on that box, and how much is in use
normally ? It sounds like the system got pushed into swapping by opening
that file.

> Even after the user had killed the process it took quite some while for
> the system to recover and I seemed to notice improvements of certain
> services after having restarted them.
> What are my options to limit resource usage for users? I tried renicing

	Take a look at login.conf it lets you define many limits by login
class - you can assign users to classes using vipw or chpass and of course
with adduser when adding new users.

> the user's process but to no help and the problem was most certainly with
> disk I/O. I don't want a normal user being able to lock up my entire
> system just by viewing text files. So any ideas?

	Very likely the problem was due to memory use and you are tight on
memory for your normal load.

Steve O'Hara-Smith <steve at>

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