sssd and ldap authentication cache

Question

On our box running OpenSUSE 12.2 we have installed OpenLDAP and sssd daemon. We are using these two services for user authentication. Recently we created a script which creates new web-users for our vhosts dynamically, but now we are dealing with a problem.

It seems that sssd uses some kind of cache and during getent passwd it returns users that have been deleted from LDAP. Sometimes it doesn't return recently created user immediately as it is necessary further in the script (for setting permissions with setfacl and chown).

Restarting LDAP, sssd or nscd doesn’t help, neither flushing cache with sss_cache -U. We tried lowering cache in config of sssd but it seems that it doesn’t affect anything.

We need to somehow explicitly refresh the cache after adding new user to LDAP or disable the cache at all.

Has anyone experienced similar issue?

Answer 1

Try sss_cache -E

or try stopping sssd, removing the files in /var/lib/sss/db/*, and restarting sssd

Answer 2

From the man page (sssd.conf):

NSS configuration options These options can be used to configure the Name Service Switch (NSS) service. enum_cache_timeout (integer) How many seconds should nss_sss cache enumerations (requests for info about all users) Default: 120 

I would insert something like:

[nss] enum_cache_timeout 10 

(adjust seconds as it seems fit)

Answer 3

I have expierenced similar issues

I noticed that getent passwd | grep <username> and getent passwd <username> will not return the same results,

Using strace I found that getent passwd <username> checks data in "/var/lib/sss/mc/passwd"

wheras getent passwd | grep <username> will connect to /var/lib/sss/pipes/nss and get it's data from there.

This is really confusing me, since both approaches seem to hit different caches. These caches seem to get updated when I run sudo su - <username> but seem to otherwise be valid for hours.

The result in practice is that e.g. ssh access won't work for a user a few minutes after it is removed from the ldap, but getent passwd will keep on showing it for hours, so it's hard for me to check if this users is in fact removed or not (without clearing some caches manually all the time)

Disabling caches is not an option in this case, having 2000+ users running jobs on 2000+ servers.

Answer 4

You could try to disable caching credentials by adding directive to /etc/sssd/sssd.conf:

[domain/default] cache_credentials = False 

You may then verify that sssd uses cache on credentials with console command:

# authconfig --test|grep credential credential caching in SSSD is disabled 

Answer 5

• You can't disable caching completely with sssd.

• You can disable sss as an authentication provider completely and just query LDAP directly if that's what you want.

For example, in /etc/nsswitch.conf, change lines like:

passwd: files sss 

to

passwd: files ldap 

• You can force cleaning of the cache by removing /var/lib/sss/db/*

Answer 6

Notice that having cache_credentials = True in Fedora 30/31 gives an error that makes impossible to login using LDAP users. I haven't found a documented bug related to this so I write it here.