Commands for Troubleshooting NFS Problems
These commands can be useful when troubleshooting NFS problems.
You can use this command to gather statistical information about NFS and RPC connections. The syntax of the command is as follows:
nfsstat [ -cmnrsz ]
If no options are supplied on the command line, the -cnrs options are used.
Gathering server-side statistics can be important for debugging problems when new software or new hardware is added to the computing environment. Running this command a minimum of once a week, and storing the numbers, provides a good history of previous performance.
Refer to the following example:
# nfsstat -s Server rpc: Connection oriented: calls badcalls nullrecv badlen xdrcall dupchecks dupreqs 719949194 0 0 0 0 58478624 33 Connectionless: calls badcalls nullrecv badlen xdrcall dupchecks dupreqs 73753609 0 0 0 0 987278 7254 Server nfs: calls badcalls 787783794 3516 Version 2: (746607 calls) null getattr setattr root lookup readlink read 883 0% 60 0% 45 0% 0 0% 177446 23% 1489 0% 537366 71% wrcache write create remove rename link symlink 0 0% 1105 0% 47 0% 59 0% 28 0% 10 0% 9 0% mkdir rmdir readdir statfs 26 0% 0 0% 27926 3% 108 0% Version 3: (728863853 calls) null getattr setattr lookup access 1365467 0% 496667075 68% 8864191 1% 66510206 9% 19131659 2% readlink read write create mkdir 414705 0% 80123469 10% 18740690 2% 4135195 0% 327059 0% symlink mknod remove rmdir rename 101415 0% 9605 0% 6533288 0% 111810 0% 366267 0% link readdir readdirplus fsstat fsinfo 2572965 0% 519346 0% 2726631 0% 13320640 1% 60161 0% pathconf commit 13181 0% 6248828 0% Version 4: (54871870 calls) null compound 266963 0% 54604907 99% Version 4: (167573814 operations) reserved access close commit 0 0% 2663957 1% 2692328 1% 1166001 0% create delegpurge delegreturn getattr 167423 0% 0 0% 1802019 1% 26405254 15% getfh link lock lockt 11534581 6% 113212 0% 207723 0% 265 0% locku lookup lookupp nverify 230430 0% 11059722 6% 423514 0% 21386866 12% open openattr open_confirm open_downgrade 2835459 1% 4138 0% 18959 0% 3106 0% putfh putpubfh putrootfh read 52606920 31% 0 0% 35776 0% 4325432 2% readdir readlink remove rename 606651 0% 38043 0% 560797 0% 248990 0% renew restorefh savefh secinfo 2330092 1% 8711358 5% 11639329 6% 19384 0% setattr setclientid setclientid_confirm verify 453126 0% 16349 0% 16356 0% 2484 0% write release_lockowner illegal 3247770 1% 0 0% 0 0% Server nfs_acl: Version 2: (694979 calls) null getacl setacl getattr access getxattrdir 0 0% 42358 6% 0 0% 584553 84% 68068 9% 0 0% Version 3: (2465011 calls) null getacl setacl getxattrdir 0 0% 1293312 52% 1131 0% 1170568 47%
The previous listing is an example of NFS server statistics. The first five lines relate to RPC and the remaining lines report NFS activities. In both sets of statistics, knowing the average number of badcalls or calls and the number of calls per week can help identify a problem. The badcalls value reports the number of bad messages from a client. This value can indicate network hardware problems.
Some of the connections generate write activity on the disks. A sudden increase in these statistics could indicate trouble and should be investigated. For NFS version 2 statistics, the connections to note are setattr, write, create, remove, rename, link, symlink, mkdir, and rmdir. For NFS version 3 and version 4 statistics, the value to watch is commit. If the commit level is high in one NFS server, compared to another almost identical server, check that the NFS clients have enough memory. The number of commit operations on the server grows when clients do not have available resources.
This command displays a stack trace for each process. The pstack command must be run by the owner of the process or by root. You can use pstack to determine where a process is hung. The only option that is allowed with this command is the PID of the process that you want to check. See the proc(1) man page.
The following example is checking the nfsd process that is running.
# /usr/bin/pgrep nfsd 243 # /usr/bin/pstack 243 243: /usr/lib/nfs/nfsd -a 16 ef675c04 poll (24d50, 2, ffffffff) 000115dc ???????? (24000, 132c4, 276d8, 1329c, 276d8, 0) 00011390 main (3, efffff14, 0, 0, ffffffff, 400) + 3c8 00010fb0 _start (0, 0, 0, 0, 0, 0) + 5c
The example shows that the process is waiting for a new connection request, which is a normal response. If the stack shows that the process is still in poll after a request is made, the process might be hung. Follow the instructions in How to Restart NFS Services to fix this problem. Review the instructions in NFS Troubleshooting Procedures to fully verify that your problem is a hung program.
This command generates information about the RPC service that is running on a system. You can also use this command to change the RPC service. Many options are available with this command. See the rpcinfo(1M) man page. The following is a shortened synopsis for some of the options that you can use with the command.
rpcinfo [ -m | -s ] [ hostname ]
rpcinfo -T transport hostname [ progname ]
rpcinfo [ -t | -u ] [ hostname ] [ progname ]
If no value is given for hostname, the local host name is used. You can substitute the RPC program number for progname, but many users can remember the name and not the number. You can use the -p option in place of the -s option on those systems that do not run the NFS version 3 software.
The data that is generated by this command can include the following:
The following example gathers information about the RPC services that are running on a server. The text that is generated by the command is filtered by the sort command to make the output more readable. Several lines that list RPC services have been deleted from the example.
% rpcinfo -s bee |sort -n program version(s) netid(s) service owner 100000 2,3,4 udp6,tcp6,udp,tcp,ticlts,ticotsord,ticots rpcbind superuser 100001 4,3,2 ticlts,udp,udp6 rstatd superuser 100002 3,2 ticots,ticotsord,tcp,tcp6,ticlts,udp,udp6 rusersd superuser 100003 3,2 tcp,udp,tcp6,udp6 nfs superuser 100005 3,2,1 ticots,ticotsord,tcp,tcp6,ticlts,udp,udp6 mountd superuser 100007 1,2,3 ticots,ticotsord,ticlts,tcp,udp,tcp6,udp6 ypbind superuser 100008 1 ticlts,udp,udp6 walld superuser 100011 1 ticlts,udp,udp6 rquotad superuser 100012 1 ticlts,udp,udp6 sprayd superuser 100021 4,3,2,1 tcp,udp,tcp6,udp6 nlockmgr superuser 100024 1 ticots,ticotsord,ticlts,tcp,udp,tcp6,udp6 status superuser 100029 3,2,1 ticots,ticotsord,ticlts keyserv superuser 100068 5 tcp,udp cmsd superuser 100083 1 tcp,tcp6 ttdbserverd superuser 100099 3 ticotsord autofs superuser 100133 1 ticots,ticotsord,ticlts,tcp,udp,tcp6,udp6 - superuser 100134 1 ticotsord tokenring superuser 100155 1 ticots,ticotsord,tcp,tcp6 smserverd superuser 100221 1 tcp,tcp6 - superuser 100227 3,2 tcp,udp,tcp6,udp6 nfs_acl superuser 100229 1 tcp,tcp6 metad superuser 100230 1 tcp,tcp6 metamhd superuser 100231 1 ticots,ticotsord,ticlts - superuser 100234 1 ticotsord gssd superuser 100235 1 tcp,tcp6 - superuser 100242 1 tcp,tcp6 metamedd superuser 100249 1 ticots,ticotsord,ticlts,tcp,udp,tcp6,udp6 - superuser 300326 4 tcp,tcp6 - superuser 300598 1 ticots,ticotsord,ticlts,tcp,udp,tcp6,udp6 - superuser 390113 1 tcp - unknown 805306368 1 ticots,ticotsord,ticlts,tcp,udp,tcp6,udp6 - superuser 1289637086 1,5 tcp - 26069
The following two examples show how to gather information about a particular RPC service by selecting a particular transport on a server. The first example checks the mountd service that is running over TCP. The second example checks the NFS service that is running over UDP.
% rpcinfo -t bee mountd program 100005 version 1 ready and waiting program 100005 version 2 ready and waiting program 100005 version 3 ready and waiting % rpcinfo -u bee nfs program 100003 version 2 ready and waiting program 100003 version 3 ready and waiting
This command is often used to watch for packets on the network. The snoop command must be run as root. The use of this command is a good way to ensure that the network hardware is functioning on both the client and the server. Many options are available. See the snoop(1M) man page. A shortened synopsis of the command follows:
snoop [ -d device ] [ -o filename ] [ host hostname ]
The -d device option is useful on those servers that have multiple network interfaces. You can use many expressions other than setting the host. A combination of command expressions with grep can often generate data that is specific enough to be useful.
When troubleshooting, make sure that packets are going to and from the proper host. Also, look for error messages. Saving the packets to a file can simplify the review of the data.
You can use this command to check if a process is hung. The truss command must be run by the owner of the process or by root. You can use many options with this command. See the truss(1) man page. A shortened syntax of the command follows.
truss [ -t syscall ] -p pid
The syscall can be a comma-separated list of system calls to be traced. Also, starting syscall with an ! selects to exclude the listed system calls from the trace.
This example shows that the process is waiting for another connection request from a new client.
# /usr/bin/truss -p 243 poll(0x00024D50, 2, -1) (sleeping...)
The previous example shows a normal response. If the response does not change after a new connection request has been made, the process could be hung. Follow the instructions in How to Restart NFS Services to fix the hung program. Review the instructions in NFS Troubleshooting Procedures to fully verify that your problem is a hung program.