System-auth and password-auth must be updated when --passalgo is set, so that is not a bug.

Please attach /etc/nsswitch.conf and /etc/sysconfig/authconfig files before and after the 'authconfig --passalgo=sha512 --update' call.

Hello, 
I'm attaching the files as well. Following are results of testing.

[root@rhel7-ipa-2 ~]# egrep -v '#' /etc/nsswitch.conf|awk NF
passwd:     files sss vas4
shadow:     files sss vas4
group:      files sss vas4
hosts:      files dns
bootparams: nisplus [NOTFOUND=return] files
ethers:     files
netmasks:   files
networks:   files
protocols:  files
rpc:        files
services:   files sss
netgroup:   files sss
publickey:  nisplus
automount:  files sss
aliases:    files nisplus
sudoers: files sss vas4


[root@rhel7-ipa-2 ~]# cat /etc/sysconfig/authconfig 
IPADOMAINJOINED=no
USEMKHOMEDIR=no
USEPAMACCESS=no
CACHECREDENTIALS=yes
USESSSDAUTH=yes
USESHADOW=yes
USEWINBIND=no
PASSWDALGORITHM=sha256
FORCELEGACY=no
USEFPRINTD=no
USEHESIOD=no
FORCESMARTCARD=no
USEDB=no
USELDAPAUTH=no
IPAV2NONTP=no
WINBINDKRB5=no
USELOCAUTHORIZE=yes
USEECRYPTFS=no
USEIPAV2=no
USEWINBINDAUTH=no
USESMARTCARD=no
USELDAP=no
USENIS=no
USEKERBEROS=no
USESYSNETAUTH=no
USESSSD=yes
USEPWQUALITY=yes
USEPASSWDQC=no



After:
[root@rhel7-ipa-2 ~]# egrep -v '#' /etc/nsswitch.conf|awk NF
passwd:     files sss
shadow:     files sss
group:      files sss
hosts:      files dns
bootparams: nisplus [NOTFOUND=return] files
ethers:     files
netmasks:   files
networks:   files
protocols:  files
rpc:        files
services:   files sss
netgroup:   files sss
publickey:  nisplus
automount:  files sss
aliases:    files nisplus
sudoers: files sss vas4



[root@rhel7-ipa-2 ~]# cat /etc/sysconfig/authconfig 
IPADOMAINJOINED=no
USEMKHOMEDIR=no
USEPAMACCESS=no
CACHECREDENTIALS=yes
USESSSDAUTH=yes
USESHADOW=yes
USEWINBIND=no
USESSSD=yes
USEDB=no
FORCELEGACY=no
USEFPRINTD=no
FORCESMARTCARD=no
USELDAPAUTH=no
USEPASSWDQC=no
IPAV2NONTP=no
WINBINDKRB5=no
USELDAP=no
USEECRYPTFS=no
USEIPAV2=no
USEWINBINDAUTH=no
USESMARTCARD=no
USELOCAUTHORIZE=yes
USENIS=no
USEKERBEROS=no
USESYSNETAUTH=no
PASSWDALGORITHM=sha512
USEPWQUALITY=yes
USEHESIOD=no

OK, I can reproduce the problem with these settings - particularly the USESSSD=yes causes the issue. If the authconfig sets up the SSSD in the 'managed' mode - i.e. USEKERBEROS and USELDAP is set to yes and USESSSD is set to no, then this problem does not happen. However if the SSSD is not managed by authconfig and thus USESSSD is set to yes, the file will get overwritten.

I can try to work on patch but I cannot guarantee it will get into RHEL-7.3 as this area of the authconfig code is very brittle and I do not want to cause a regression for other customers.

I am setting tentatively a devel_ack.

Just note that the fix for this bug will make authconfig to not touch nsswitch.conf if it thinks it does not need update. For example if I remove sss from some of the nsswitch.conf entries but not from the 'passwd:' entry and I issue authconfig --enablesssd --update, it will not update nsswitch.conf. The reader for the nsswitch.conf in authconfig is simple and cannot recognize all the various configurations or misconfigurations that someone can invent.

In general if there is known-inconsistent state of the authentication and identity configuration and it is needed to make it consistent, it is better to call authconfig --updateall.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2462.html