Maintenance of /etc/fstab in large network Crashed NFS server will make operation blocked

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Elwin Burke
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1 Automount NFS

2 Automatic mounting Problems of /etc/fstab Maintenance of /etc/fstab in large network Crashed NFS server will make operation blocked Only a relatively small number of remote filesystems (exports) will be active at any given time automount daemon Mount filesystems when they are referenced and unmount them when they are no longer needed Supply a list of replicated filesystems to replace important but crashed NFS servers Transparent to users Products automount (from SUN Micro), simple and concise amd (from Jan-Simon Pendry), complicated but more powerful 2

3 automount (1) Three kinds of configuration files (map) Direct map Indirect map Master map List which direct and indirect maps that automount should pay attention to Difference between direct and indirect Provide information about filesystems that are to be automounted All mount points in indirect map has common directory defined in master map 3

4 automount (2) Example of automount maps master indirect /net /etc/auto.net -rw, intr /- /etc/auto.direct -ro, intr WWW -rw,soft,nosuid,vers=2 vega:/home/www mail -rw,soft,nosuid,quota ccserv:/spool/mail ftp -ro,soft,nosuid ftp:/home/ftp direct /vlsi/vlsi1 -rw,soft,nosuid scorpio:/vlsi1 /vlsi/vlsi2 -rw,soft,nosuid scorpio:/vlsi2 4

5 automount (3) Master map /etc/auto.master (Linux) /etc/auto_master (Solaris) Restart automounter when you change the maps /etc/init.d/autofs {start stop} (Solairs) /etc/init.d/autofs {start stop reload status} (Linux) 5

6 automount (4) Replicated filesystem There are several identical NFS and I would like to mount anyone of them Constrain Read-only These replicated filesystem should be truly identical Automounter will choose a server based on its own idea of which one is the best /usr/man -ro chimchim:/usr/man band(1):/usr/man /www/data -ro ccbsd4,altair:/www/data 6

7 automount (5) Automatic automounts automount can query the mountd to find out what filesystems the server exports Using host as map name in the master map file /net -host -nosuid,soft -host does not enumerate all possible hosts It waits for individual subdirectory names to be referenced If chimchim exports /usr/share/man Automount at the path /net/chimchim/usr/share/man 7

8 Linux autofs autofs Format of the automounter maps /etc/auto.master man 5 autofs Indirect map kernel -ro,soft,intr ftp.kernel.org:/pub/linux boot -fstype=ext2 :/dev/hda1 windoze -fstype=smbfs ://windoze/c path host1(5),host2(6),host3(1):/path/path Direct map /nfs/apps/mozilla /nfs/data/budgets /tst/sbin bogus:/usr/local/moxill tiger:/usr/local/budgets bogus:/usr/sbin 8

9 amd (1) Advantages over automount Sends keep alive queries to remote servers at regular intervals and maintains a list of servers that are accessible Return an operation would block rather than hanging Not proprietary source code Offer another mount types that are not supported by automount union Map syntax is more generic Provide a query-and-manipulation tool, amq 9

10 amd (2) Flexible map syntax One map used by many machines Contain conditions that control which parts of map entry are activate Selector variable /defaults type:=nfs;fs:=${autodir}/${key};opts:=nfsv3,rw, \ grpid,quota,intr,soft,nodev,nosuid,resvport, \ timeo=10,retrans=5,nqnfs mail rhost:=ccserv;rfs:=/spool/mail ftp raid1 rhost:=ftp;rfs:=/home/ftp host==cchome;type:=ufs;dev:=/dev/da0s1e\ host!=cchome;type:=nfs;rhost:=cchome;rfs:=/${key};\ opts:=nfsv3,rw,soft,nosuid,resvport drongo host==magpie;type:=link;fs:=/${key} \ host!=magpie;type:=nfs;rhost:=magpie;rfs:=/${key} 10

11 amd (3) Selector arch autodir domain host key map os Description Architecture of the current machine Default directory under which to mount filesystems Local NIS domain name Local hostname Volume name being resolved Name of mount map being used Operating System 11 Option rhost rfs type fs opts remopts Description Remote host on which the volume lives Remote filesystem name Type of mount, nfs or ufs (local disk) Local mount point Mount options Options to use if server is nonlocal

12 amd (4) Starting amd % amd a /tmp_mnt l syslog x fatal, error, user /net /etc/amd.conf Stopping amd options % kill -15 <amd_pid> Description -x Sets run-time logging options, such as fatal, error, user, warn, info, -r Restart existing mounts -l Log file name or syslog -a Specify alternative location for mount points /net /etc/amd.conf The map files Sets the automount directory 12

13 amd (5) Remount without kill amd Unmount such mounted partition % umount /amd/magpie Delete such virtual /net/dir % rm /net/magpie cd /net/dir % cd /net/magpie amd in FreeBSD Edit rc.conf 13 amd_enable= YES amd_flags= -a /amd y sa.nis l /var/log/amd.log x all /net auto.home

14 amq amq Provides a simple way of determining the current state of the amd(8) program Amd implements an RPC interface which is used by the amq program bsd5[~] -chiahung- amq / root "root" /net toplvl amd.map /net /net/mail nfsl netapp:/vol/mail /amd/mail /net/cs nfsl netapp2:/vol/home/cs /amd/cs /net/dcs nfsl netapp2:/vol/home/dcs /amd/dcs /net/gcs nfsl netapp2:/vol/home/gcs /amd/gcs bsd5[~] -chiahung- amq -s requests stale mount mount unmount deferred fhandles ok failed failed

Network File System Andrew File System NetWare Core Protocol Server Message Block Common Internet File System

Network File System Andrew File System NetWare Core Protocol Server Message Block Common Internet File System Share filesystem to other hosts via network NFS History Introduced by Sun Microsystems in 1985