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NFSv4 mount incorrectly shows all files with ownership as nobody:nobody

2016-09-01 15:27 梁小白 阅读(...) 评论(...) 编辑 收藏
NFSv4 mount incorrectly shows all files with ownership as nobody:nobody
 
 SOLUTION VERIFIED - Updated February 18 2016 at 5:48 PM - 
Environment
  • Red Hat Enterprise Linux 5
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • NFSv4 share being exported from an NFSv4 capable NFS server
Issue
  • From the client, the mounted NFSv4 share has ownership for all files and directories listed as nobody:nobody instead of the actual user that owns them on the NFSv4 server, or who created the new file and directory.
  • Seeing nobody:nobody permissions on nfsv4 shares on the nfs client. Also seeing the following error in /var/log/messages:
nss_getpwnam: name 'root@example.com' does not map into domain 'localdomain' 
Resolution
  • Modify the /etc/idmapd.conf with the proper domain (FQDN), on both the client and server. In this example, the proper domain is "example.com" so the "Domain =" directive within /etc/idmapd.conf should be modified to read:
Domain = example.com
  • Note:
  • If using a NetApp Filer, the NFS.V4.ID.DOMAIN parameter must be set to match the "Domain =" parameter on the client.
  • If using a Solaris machine as the NFS server, the NFSMAPID_DOMAIN value in /etc/default/nfs must match the RHEL clients Domain.
  • To put the changes into effect restart the rpcidmapd service and remount the NFSv4 filesystem:
# service rpcidmapd restart
# mount -o remount /nfs/mnt/point
Note: It is only necessary to restart rpc.idmapd service on systems where rpc.idmapd is actually performing the id mapping. On RHEL 6.3 and newer NFS CLIENTS, the maps are stored in the kernel keyring and the id mapping itself is performed by the /sbin/nfsidmap program. On older NFS CLIENTS (RHEL 6.2 and older) as well as on all NFS SERVERS running RHEL, the id mapping is performed by rpc.idmapd.
  • Ensure the client and server have matching UID's and GID's. It is a common misconception that the UID's and GID's can differ when using NFSv4. The sole purpose of id mapping is to map an id to a name and vice-versa. ID mapping is not intended as some sort of replacement for managing id's.
  • On Red Hat Enterprise Linux 6, if the above settings have been applied and UID/GID's are matched on server and client and users are still being mapped to nobody:nobody than a clearing of the idmapd cache may be required:
 # nfsidmap -c 
Note: The above command is only necessary on systems that use the keyring-based id mapper, i.e. NFS CLIENTS running RHEL 6.3 and higher. On RHEL 6.2 and older NFS CLIENTS as well as all NFS SERVERS running RHEL, the cache should be cleared out when rpc.idmapd is restarted.
  • Another check, see if the passwd:, shadow: and group: settings are set correctly in the /etc/nsswitch.conf file on both Server and Client.
Disabling idmapping
  • By default, RHEL6.3 and newer NFS clients and servers disable idmapping when utilizing the AUTH_SYS/UNIX authentication flavor by enabling the following booleans:
NFS client 
 # echo 'Y' > /sys/module/nfs/parameters/nfs4_disable_idmapping 
 
NFS server
 # echo 'Y' > /sys/module/nfsd/parameters/nfs4_disable_idmapping 
  • If using a NetApp filer, the options nfs.v4.id.allow_numerics on command can be used to disable idmapping. More information can be foundhere.
  • With this boolean enabled, NFS clients will instead send numeric UID/GID numbers in outgoing attribute calls and NFS servers will send numeric UID/GID numbers in outgoing attribute replies.
  • If NFS clients sending numeric UID/GID values in a SETATTR call receive an NFS4ERR_BADOWNER reply from the NFS server clients will re-enable idmapping and send user@domain strings for that specific mount from that point forward.
Note: This option can only be used with AUTH_SYS/UNIX authentication flavors, if you wish to use something like Kerberos, idmapping must be used.
Root Cause
  • NFSv4 utilizes ID mapping to ensure permissions are set properly on exported shares, if the domains of the client and server do not match then the permissions are mapped to nobody:nobody.
Diagnostic Steps
  • Debugging/verbosity can be enabled by editing /etc/sysconfig/nfs:
RPCIDMAPDARGS="-vvv"
  • The following output is shown in /var/log/messages when the mount has been completed and the system shows nobody:nobody as user and group permissions on directories and files:
Jun  3 20:22:08 node1 rpc.idmapd[1874]: nss_getpwnam: name 'root@example.com' does not map into domain 'localdomain' 
Jun  3 20:25:44 node1 rpc.idmapd[1874]: nss_getpwnam: name 'root@example.com' does not map into domain 'localdomain'
  • Collect a tcpdump of the mount attempt:
# tcpdump -s0 -i {INTERFACE} host {NFS.SERVER.IP} -w /tmp/{casenumber}-$(hostname)-$(date +"%Y-%m-%d-%H-%M-%S").pcap & 
  • If a TCP packet capture has been obtained, check for a nfs.nfsstat4 packet that has returned a non-zero response equivalent to 10039 (NFSV4ERR_BADOWNER).
  • From the NFSv4 RFC:
  NFS4ERR_BADOWNER        = 10039,/* owner translation bad   */
 
  NFS4ERR_BADOWNER      An owner, owner_group, or ACL attribute value
                        can not be translated to local representation.
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