How to purge sssd cache

[Varun Mittal3]

Hi

We are using sssd available on RHEL 7 and have a query on purging sssd
cache incase domain goes offline.
We are using just the UID/GID and group membership for users. And netgroups
(both LDAP and NIS proxy) in some cases

As I understand, sss_cache utility only invalidates the records, which
marks them expired. Whenever the domain is online, these will be refreshed.
But if the domain is offline, those expired records will still be returned
as valid.

- Please reconfirm if this understanding is correct
- And if this is correct, then is there a way to purge the records to
return users/group queries invalid if domain is offline

Thanx & Regards,
Varun Mittal

[Lukas Slebodnik]

On (07/03/15 18:56), Varun Mittal3 wrote:
> Hi
>
> We are using sssd available on RHEL 7 and have a query on purging sssd
> cache incase domain goes offline.
> We are using just the UID/GID and group membership for users. And netgroups
> (both LDAP and NIS proxy) in some cases
>
> As I understand, sss_cache utility only invalidates the records, which
> marks them expired. Whenever the domain is online, these will be refreshed.
> But if the domain is offline, those expired records will still be returned
> as valid.

SSSD periodically removed cached expired objects. By default periodic clean-up
task is executed every 3 hours.
    Details: man sssd-ldap -> ldap_purge_cache_timeout

Entries will not removed from sssd cache if user successfuly authenticate
and option "cache_credentials" is enabled.
    Details: man sssd.conf -> cache_credentials
                           -> offline_credentials_expiration
                           -> offline_failed_login_attempts

The last configuration option you should look at is
entry_cache_timeout. The value of this option tells how long
is cached entry valid.
    Details: man sssd.conf -> entry_cache_timeout

BTW. There is a still chance that entry can be returned even thought
it was removed from sssd cache. The reason is that sssd uses the fast memory
cache on client side and value are cached by default for 300 seconds.
    Details: man sssd.conf -> memcache_timeout

Could you describe your use case for purging sssd cache
or could you explain why do you need it.

LS

[Varun Mittal3]

> From: Lukas Slebodnik 
> To: End-user discussions about the System Security Services Daemon
>
> Date: 03/07/2015 07:14 PM
> Subject: Re: [SSSD-users] How to purge sssd cache
> Sent by: [e-mail]
>
> On (07/03/15 18:56), Varun Mittal3 wrote:
> > Hi
> >
> > We are using sssd available on RHEL 7 and have a query on purging sssd
> > cache incase domain goes offline.
> > We are using just the UID/GID and group membership for users. And

netgroups
> > (both LDAP and NIS proxy) in some cases
> >
> > As I understand, sss_cache utility only invalidates the records, which
> > marks them expired. Whenever the domain is online, these will be

refreshed.
> > But if the domain is offline, those expired records will still be

returned
> > as valid.
>
> SSSD periodically removed cached expired objects. By default periodic

clean-up
> task is executed every 3 hours.
>     Details: man sssd-ldap -> ldap_purge_cache_timeout
>
> Entries will not removed from sssd cache if user successfuly authenticate
> and option "cache_credentials" is enabled.
>     Details: man sssd.conf -> cache_credentials
>                            -> offline_credentials_expiration
>                            -> offline_failed_login_attempts

We are not using sssd for authentication. Just UID/GID, group
memberships,
    names and netgroups lookup for NFS use cases
> The last configuration option you should look at is
> entry_cache_timeout. The value of this option tells how long
> is cached entry valid.
>     Details: man sssd.conf -> entry_cache_timeout
>
> BTW. There is a still chance that entry can be returned even thought
> it was removed from sssd cache. The reason is that sssd uses the fast

memory
> cache on client side and value are cached by default for 300 seconds.
>     Details: man sssd.conf -> memcache_timeout
>
> Could you describe your use case for purging sssd cache
> or could you explain why do you need it.
>
> LS

Ours is mostly NFS use case where the NFS server will need to resolve
names,
    group members, netgroup etc. And the admin may want to purge some
    specific entry in case that is modified/removed from the directory
server.
    So the NFS server must immediately delete that entry even if the
domain is
    offline to avoid security issues.

[Ashish Yadav]

Hi,

On 7 Mar 2015 18:56, "Varun Mittal3"  wrote:
> Hi
>
> We are using sssd available on RHEL 7 and have a query on purging sssd

cache incase domain goes offline.
> We are using just the UID/GID and group membership for users. And

netgroups(both LDAP and NIS proxy) in some cases
> As I understand, sss_cache utility only invalidates the records, which

marks them expired. Whenever the domain is online, these will be refreshed.
But if the domain is offline, those expired records will still be returned
as valid.
> Please reconfirm if this understanding is correct
> And if this is correct, then is there a way to purge the records to

return users/group queries invalid if domain is offline
>

I haven't tried on CentOS 7 but it should be done by doing below given
steps as far as sssd is concerned. This is a manual procedure, if you want
automatic procedure then look into cache_timeout option in sssd.

1. service sssd stop
2. cd /var/lib/sss/db
3. rm -rf *
4. service sssd start

--Regards
Ashishkumar S. Yadav

[Varun Mittal3]

> From: Ashish Yadav 
> To: End-user discussions about the System Security Services Daemon
>
> Date: 03/08/2015 09:23 AM
> Subject: Re: [SSSD-users] How to purge sssd cache
> Sent by: [e-mail]
>
> Hi,
> On 7 Mar 2015 18:56, "Varun Mittal3"  wrote:
> > Hi
> >
> > We are using sssd available on RHEL 7 and have a query on purging
>
> sssd cache incase domain goes offline.
> > We are using just the UID/GID and group membership for users. And
>
> netgroups(both LDAP and NIS proxy) in some cases
> > As I understand, sss_cache utility only invalidates the records,
>
> which marks them expired. Whenever the domain is online, these will
> be refreshed. But if the domain is offline, those expired records
> will still be returned as valid.
> > Please reconfirm if this understanding is correct
> > And if this is correct, then is there a way to purge the records
>
> to return users/group queries invalid if domain is offline
> >
>
> I haven't tried on CentOS 7 but it should be done by doing below
> given steps as far as sssd is concerned. This is a manual procedure,
> if you want automatic procedure then look into cache_timeout option in

sssd.

Reading about cache_timeout from man page, that also looks like it
will
    only mark the records invalid not purge them
> service sssd stop
> cd /var/lib/sss/db
> rm -rf *
> service sssd start

Yeah, I tested this on RHEL. This seems to work but then it will
purge
    all the records for any domain. I wouldn't be able to purge a single
    record with this.

[Ashish Yadav]

Hi,

On Sun, Mar 8, 2015 at 10:16 AM, Varun Mittal3 
wrote:
> > From: Ashish Yadav 
> > To: End-user discussions about the System Security Services Daemon
> >
> > Date: 03/08/2015 09:23 AM
> > Subject: Re: [SSSD-users] How to purge sssd cache
> > Sent by: [e-mail]
> >
> > Hi,
> > On 7 Mar 2015 18:56, "Varun Mittal3"  wrote:
> > > Hi
> > >
> > > We are using sssd available on RHEL 7 and have a query on purging
> >
> > sssd cache incase domain goes offline.
> > > We are using just the UID/GID and group membership for users. And
> >
> > netgroups(both LDAP and NIS proxy) in some cases
> > > As I understand, sss_cache utility only invalidates the records,
> >
> > which marks them expired. Whenever the domain is online, these will
> > be refreshed. But if the domain is offline, those expired records
> > will still be returned as valid.
> > > Please reconfirm if this understanding is correct
> > > And if this is correct, then is there a way to purge the records
> >
> > to return users/group queries invalid if domain is offline
> > >
> >
> > I haven't tried on CentOS 7 but it should be done by doing below
> > given steps as far as sssd is concerned. This is a manual procedure,
> > if you want automatic procedure then look into cache_timeout option in
>
> sssd.
>
> Reading about cache_timeout from man page, that also looks like it will
>  only mark the records invalid not purge them
> > service sssd stop
> > cd /var/lib/sss/db
> > rm -rf *
> > service sssd start
>
> Yeah, I tested this on RHEL. This seems to work but then it will purge
>  all the records for any domain. I wouldn't be able to purge a single
>  record with this.

If you have multiple domain then delete the specific domain's file only.
All files should be consisting
domain name in their filename.

--Regards
Ashishkumar S. Yadav

[Jakub Hrozek]

On Sun, Mar 08, 2015 at 10:16:51AM +0530, Varun Mittal3 wrote:
> > service sssd stop
> > cd /var/lib/sss/db
> > rm -rf *
> > service sssd start
>
> Yeah, I tested this on RHEL. This seems to work but then it will
> purge
>    all the records for any domain. I wouldn't be able to purge a single
>    record with this.

This works, but:
    1) Since the cache also stores the password hashes, you lock
    yourself out of the client if you remove the cache while offline.
    You might consider just moving the cache instead.

2) As Lukas said, there is a second cache layer since 1.9 that
    is stored as /var/lib/sss/mc/