Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 2 ■ CENTRALIZING YOUR NETWORK: KERBEROS, LDAP, AND NFSdn: cn=jkemp,ou=auto.home,dc=example,dc=comobjectClass: automountcn: jkempautomountInformation: -fstype=nfs,rw server1:/export/home/jkempautomountMapName: auto_homeAuthenticate as the LDAP admin user (kinit ldapadm if you’re using Kerberos), and add theseentries to the database:ldapadd < automount.ldifYou should now be able to automount /home/jkemp from your client. Repeat this for your otherusers.2-15. Connecting Macs to a <strong>Linux</strong> NFS ServerIf you have Macs on your network that want to be able to connect to an NFS server, you will run into theproblem that <strong>Linux</strong> NFS expects clients to use a privileged network port (less than 1024); while Mac (andother OpenBSD-based systems) use a port above 1024 for NFS requests.There are two ways of solving this. The first is to add the insecure parameter to the /etc/exports fileon the server:/local 10.1.0.*rw,insecureIf you prefer and you have only one or two Macs, you could do this for only them in particular:/local 10.1.0.17/local 10.1.0.*rw,insecurerwThe other option is to fix it at the client end. This is probably neater but may cause you moreproblems with users, depending on your setup. You need to add -P to the command line (one of the userproblems here is that you can’t do this from the Finder).mount -P server:/local /mnt2-16. Improving NFS PerformanceIf you’re experiencing performance problems, you can look at /proc/net/rpc/nfsd for some diagnosticinformation. For example, the th line in that file indicates the number of seconds during which thethread usage was at the maximum allowable. If this is a large number, you may want to increase thenumber of NFS instances available (that is, the number of servers running). The standard default is 8,but more heavily used servers may benefit from having more. This is specified with the RPCNFSDCOUNTvalue, which is given in the init script (/etc/init.d/nfs-kernel-server on Debian/Ubuntu).60Download at WoweBook.Com
CHAPTER 2 ■ CENTRALIZING YOUR NETWORK: KERBEROS, LDAP, AND NFS■ Note If you’re using a system on which the file /etc/default/nfs-kernel-server exists (for example,Debian/Ubuntu), then you’ll also need to set the new RPCNFSDCOUNT value in this file.If you’re experiencing load or performance issues, you can also increase the memory queue limits.These are frequently low by default, especially on 2.4 kernels, and because the memory queue is sharedbetween all the server instances, it’s probably a good idea to increase the memory queue if you increasethe number of servers. The limits are set using proc. Use /proc/sys/net/core/rmem_default and/proc/sys/net/core/rmem_max for the read limits, and use /proc/sys/net/core/wmem_default and/proc/sys/net/core/wmem_max for the read limits. Reset them to 256k as follows:# echo 262144 > /proc/sys/net/core/rmem_default# echo 262144 > /proc/sys/net/core/rmem_max# echo 262144 > /proc/sys/net/core/wmem_default# echo 262144 > /proc/sys/net/core/wmem_maxThen restart the NFS server with /etc/init.d/nfs-kernel-server.■ Note There are some reports of problems generated in other systems if these values are left unchanged forlong periods of time. You can reset them after you’ve restarted the NFS server (using the same lines as shownpreviously, but substitute 65536 for 262144). However, bear in mind that in this case, the new values will bediscarded the next time you have to restart NFS. Perhaps better is to watch for problems and reset the values ifthey arise.nfsstat -s (on the server) and nfsstat -c (on the client) may also be helpful. These both show NFSstatistics. In particular, if badcalls is greater than zero, you may have network problems, and if writes isgreater than 10 percent, it may be worth looking into write caching to speed up operation.nfsstat -m from the client provides server information from the client’s point of view. The srttgives a smoothed round-trip time value. If this is greater than 50ms, the mount point is slow. cur givesthe timeout value. If cur > 80ms for lookups, cur > 150ms for reads, and/or cur > 250ms for writes, thenthe requests are taking too long.61Download at WoweBook.Com
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Contents■About the Author .......
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■ CONTENTS3-7. Writing a Nagios P
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■ CONTENTS■Chapter 8: Using the
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■ CONTENTSAbout the Author■Juli
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■ CONTENTSAcknowledgmentsMany tha
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■ CONTENTSIntroductionThis book i
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■ INTRODUCTIONDownloading the Cod
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C H A P T E R 1■ ■ ■Saving Yo
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CHAPTER 1 ■ SAVING YOURSELF EFFOR
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Page 29 and 30: CHAPTER 1 ■ SAVING YOURSELF EFFOR
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CHAPTER 4 ■ TAKING BACKUPS AND MA
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C H A P T E R 5■ ■ ■Working w
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CHAPTER 5 ■ WORKING WITH FILESYST
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C H A P T E R 6■ ■ ■Securing
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CHAPTER 6 ■ SECURING YOUR SYSTEMS
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CHAPTER 7 ■ WORKING WITH APACHEOn
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CHAPTER 7 ■ WORKING WITH APACHEdi
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CHAPTER 7 ■ WORKING WITH APACHE4.
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CHAPTER 7 ■ WORKING WITH APACHE
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CHAPTER 7 ■ WORKING WITH APACHEAl
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CHAPTER 7 ■ WORKING WITH APACHE
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C H A P T E R 8■ ■ ■Making Be
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CHAPTER 8 ■ USING THE COMMAND LIN
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CHAPTER 9 ■ WORKING WITH TEXT IN
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C H A P T E R 10■ ■ ■Things G
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CHAPTER 10 ■ THINGS GO IN, THINGS
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C H A P T E R 11■ ■ ■Tracking
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CHAPTER 11 ■ TRACKING DOWN BUGSTh
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CHAPTER 11 ■ TRACKING DOWN BUGS01
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CHAPTER 11 ■ TRACKING DOWN BUGS
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CHAPTER 11 ■ TRACKING DOWN BUGSTh
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CHAPTER 11 ■ TRACKING DOWN BUGSAn
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CHAPTER 11 ■ TRACKING DOWN BUGS#
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C H A P T E R 12■ ■ ■Managing
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CHAPTER 12 ■ MANAGING TIME AND PE
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APPENDIX■ ■ ■Perl TipsSee rec
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APPENDIX ■ PERL TIPS• Date::Par
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APPENDIX ■ PERL TIPSPerl Syntax N
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■ ■ ■Index■Symbols$CDPATH,
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■ INDEXenscript option (printing)
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■ INDEX■NNagiosadding hosts to,
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■ INDEXsyslogcentralized logging
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Linux System Administration Recipes A Problem-Solution Approach

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