NFSv4 README Last updated: 17 May 2012 0. Contents: ----------- 1. Overview. \___ 1.1 Purpose of this document 2. Quick start 3. Idmapd Configuration on both NFS server and client 4. Setting up NFSv4 server and client \___ 4.1 Configuring Server | \___ 4.1.1 /etc/exports | \___ 4.1.2 Coexisting NFSv4 and NFSv3 | \___ 4.1.3 /etc/sysconfig/nfs \___ 4.2 Starting services on server and client \___ 4.3 Mounting the remote exported directories from client 5.Setting up kerberized NFSv4 server and client \___ 5.1 Prerequisites \___ 5.2 Configuring kerberized NFS server and client | \___ 5.2.1 Configuring kerberos | \___ 5.2.2 Create machine credentials | \___ 5.2.3 Configure /etc/gssapi_mech.conf | \___ 5.2.4 /etc/exports entries for kerberised server. \___ 5.3 Starting services on server and client \___ 5.4 Mounting the remote exported directories \___ 5.5 A known issue using NFSv4 with kerberos 6.Troubleshooting \___ 6.1 Checklist to ensure NFSv4 is up and running \___ 6.2 Checklist to ensure NFSv4 Kerberos is working properly 1. Overview: ------------ The Network File System Version 4 (NFSv4) is a distributed file system similar to previous versions of NFS in its straightforward design, and independence of transport protocols and operating systems for file access in a heterogeneous network. Unlike earlier versions of NFS, the new protocol integrates file locking, strong security, Compound RPCs (combining relevant operations), and delegation capabilities to enhance client performance for narrow data sharing applications on high-bandwidth networks. NFSv4 implementations are backward compatible with NFSv2 and NFSv3. Note: NFSv4 ACLs and krb5p (Kerberos Privacy) are currently not supported 1.1 The Purpose of this document ________________________________ This document is intended as a step-by-step guide to setup NFSv4 on openSUSE 12. It discusses NFSv4 server and client configuration. 2. Quickstart ------------- For NFSv4 server: 1) /etc/exports does not require any special entries to work with NFSv4. Earlier SUSE releases required 'fsid=0' on precisely one entry, and 'bind=' annotations on others. This is no longer required and should be removed. It is still supported, so there is no need to change /etc/exports when upgrading to openSUSE 12. 2) Edit /etc/idmapd.conf to modify the default "Domain" to contain your DNS domain name. 3) Execute the following commands to start idmapd and nfsserver #/etc/init.d/idmapd start #/etc/init.d/nfsserver start For NFSv4 client: 1) Edit /etc/idmapd.conf to modify the default "Domain" to contain your DNS domain name. 2) Execute the following command to start idmapd. #/etc/init.d/idmapd start 3) Mount the exported file system using the following command: #mount -t nfs4 :/ Observe that only "/" is given instead of the actual exported path name. 3. Idmapd Configuration on client and server -------------------------------------------- idmapd.conf - configuration file for idmapd (idmapping daemon), which does NFSV4<=>name mapping. Here dns domain (Domain) name has to be configured in both client and server. Sample Configuration file: ========================================================================== [General] Verbosity = 0 Pipefs-Directory = /var/lib/nfs/rpc_pipefs Domain = mydomain.com [Mapping] Nobody-User = nobody Nobody-Group = nobody ========================================================================== 4. Setting up NFSv4 server and client ------------------------------------- 4.1 Configuring Server ___________________________ There are three main configuration files you will need to edit to set up an NFSv4 server: /etc/sysconfig/nfs and /etc/idmapd.conf. we will describe the first here as idmapd.conf is done in previous section. 4.1.1 /etc/sysconfig/nfs ========================= /etc/sysconfig/nfs is another NFS server configuration file. Here the number of kernel threads, NFSv4 support and GSS security (kerberos) for NFS can be configured (kerberos set up is explained in Section 5.) 4.2 Starting services on server and client __________________________________________ We need to start idmapd and nfsserver on the NFSv4 server. #/etc/init.d/idmapd start #/etc/init.d/nfsserver start and start idmapd alone on the client. If the machines that are being used as client and server are just meant for that, the daemons can be enabled during bootup as shown below. Use insserv to do this #insserv -d idmapd #insserv -d nfsserver and idmapd alone on the client. 4.3 Mounting remote exported directories ________________________________________ One main difference between previous versions of NFS and NFSv4 is the way in which mount is invoked. With regard to the pseudofilesystem concept sketched above, mount is done as follows: #mount -t nfs4 :/ Observe that only '/' is given after the servername. 5. Setting up kerberized NFSv4 server and client ------------------------------------------------ 5.1 Prerequisites _________________ o Key Distribution Center (KDC) must already be set up on the network. o krb5-1.4.x must be installed on both NFS server and NFS client. o krb5-client-1.4.x must be installed on both NFS server and NFS client. o NFS server, client and the KDC server must have their time synchronized. o NFS_SECURITY_GSS has to be set to "yes" in /etc/sysconfig/nfs in both server and client. 5.2 Configuring Kerberized NFSv4 server and client __________________________________________________ All the following configuration steps except 5.2.4 are for both NFSv4 client and server. 5.2.1 Configure kerberos ======================== Edit krb5.conf. Sample configuration ========================================================================== [libdefaults] default_realm = MYDOMAIN.COM dns_lookup_realm = true dns_lookup_kdc = true [realms] MYDOMAIN.COM = { kdc = kdcserver.mydomain.com admin_server = adminserver.mydomain.com default_domain = mydomain.com } [domain_realm] mydomain.com = MYDOMAIN.COM .mydomain.com = MYDOMAIN.COM [logging] kdc = FILE:/var/log/krb5kdc.log admin_server = FILE:/var/log/kadmin.log default = FILE:/var/log/krb5lib.log ========================================================================== Replace MYDOMAIN.COM with your REALM, kdcserver.mydomain.com with your KDC server, adminserver.mydomain.com with your Admin server & mydomain.com with your DNS domain name. 5.2.2 Create machine credentials ================================ This means creating a Kerberos V5 principal/instance name of the form nfs/@REALM, and either adding a key for this principal to an existing /etc/krb5.keytab or creating an /etc/krb5.keytab. Note: only the encryption type of des-cbc-crc is functional so far in the kernel, so add only this type of key. kadmin: addprinc -e des-cbc-crc:normal nfs/@REALM kadmin: ktadd -e des-cbc-crc:normal -k /etc/krb5.keytab nfs/@REALM 5.2.3 Configure /etc/gssapi_mech.conf ===================================== This configuration file determines which GSS-API mechanisms the gssd code should use. Usually no need to modify this file in 32 bit machines because the libraries are installed in /usr/lib. Note: In case of 64 bit machines this has to be modified to /usr/lib64. This is a workaround and will be fixed later. Sample configuration ========================================================================== # GSSAPI Mechanism Definitions # # This configuration file determines which GSS-API mechanisms # the gssd code should use # # NOTE: # The initialization function "mechglue_internal_krb5_init" # is used for the MIT krb5 gssapi mechanism. This special # function name indicates that an internal function should # be used to determine the entry points for the MIT gssapi # mechanism functions. # # library initialization function # ================================ ========================== # The MIT K5 gssapi library, use special function for initialization. /usr/lib/libgssapi_krb5.so mechglue_internal_krb5_init # # The SPKM3 gssapi library function. Use the function spkm3_gss_initialize. # /usr/local/gss_mechs/spkm/spkm3/libgssapi_spkm3.so spkm3_gss_initialize ========================================================================== 5.2.4 /etc/exports entries for a kerberized server ================================================== Typical entries for kerberos security mode looks like these: /export gss/krb5(rw,insecure,no_subtree_check,sync,no_root_squash) /export gss/krb5i(rw,insecure,no_subtree_check,sync,no_root_squash) Note: i) option 'insecure' - The insecure option in this entry also allows clients with NFS implementations that don't use a reserved port for NFS. So it is advisable *NOT* to use this option unless you have a kerberised set up or you know what you are doing. 5.3 Starting the services on server and client ______________________________________________ On NFSv4 server, svcgssd needs to be started too. So, #/etc/init.d/idmapd start #/etc/init.d/svcgssd start #/etc/init.d/nfsserver start On NFSv4 client, gssd needs to be started too. So, #/etc/init.d/idmapd start #/etc/init.d/gssd start Or To avoid starting manually, enable service during bootup using insserv as mentioned in 4.2 5.4 Mounting exported directories with kerberos _______________________________________________ To mount a filesystem using krb5, provide the "-osec=krb5" option to mount. #mount -tnfs4 -osec= nfsserver:/ /mntpoint can be krb5(Autentication) or krb5i (Integrity). 5.5 A known issue using NFSv4 with kerberos ___________________________________________ Even if "no_root_squash" option is used, while exporting a filesystem at the server, root on the client gets a "Permission denied" error when creating files on the mount point. This is because there is no proper mapping between root and the GSSAuthName. Note: Trying to set 777 permission is not correct as it is not secure. Also, any file created on the mountpoint will have "nobody" as owner. There is a work around for this if both NFS server and client use ldap_umich methods to authenticate. If the idmapd on both server and client is configured to use ldap_umich modules then having GSSAuthName () parameter map to root user, on the ldap server will solve this problem. A proper fix for this issue is being worked upon. 6. Troubleshooting ------------------- 6.1 Checklist to ensure NFSV4 is up and running _______________________________________________ 1. ps -ef | grep nfsd ps -ef | grep idmapd ps -ef | grep svcgssd to check server side daemons are up and running. 2. ps -ef | grep idmapd ps -ef | grep gssd to check client side daemons are up and running 3. rpcinfo -p to check all registered RPC programs (nfs, portmapper, mountd) & versions 4. Check firewall is enabled on server/client from YAST. Yast -> Security and Users -> Firewall. Make sure NFS service is enabled. 5. showmount -e to check mount information on NFS server 6. If users are not mapped properly check whether idmapd is running in both server & client and dns domain name is properly configured. 7. If you unable to mount, check for the correctness of the exports file entry. 6.2 Check list to ensure kerberos is working properly _____________________________________________________ There are many reasons this could be failing. 1. Verify that rpc.gssd is running on the client and rpc.svcgssd is running on the server. 2. Verify that your hostnames are correct. The hostname command should return a fully-qualified hostname that has a correct DNS reverse-mapping (either through DNS or the /etc/hosts file). 3. Verify there is a keytab entry for nfs/@REALM in your keytab file (/etc/krb5.keytab). 4. Verify your Kerberos configuration file has the proper mapping from the DNS hostname to the correct realm. The [domain_realm] section of the /etc/krb5.conf needs to have a mapping from the DNS domain to the correct REALM. For example, if your nfs server's hostname is 'foo.abc.org' and your Kerberos realm name is 'ALPHABET.ORG', then you need an entry like the following in /etc/krb5.conf on the nfs client machine: [domain_realm] .abc.org = ALPHABET.ORG 5. Verify whether your ticket is not expired or not on the client using klist. If it is expired renew using kinit. This must be checked when you find "I/O Error" or "Permission denied" while doing file operations.