RHEL6–36–AUTOFS-1

RHEL6–36–AUTOFS

WHAT IS AUTOFS?

Mounted partition is a dedicated resource in NFS whereas in autofs mount & unmount are not permanent. They automatically mounted whenever accessed and unmounted if not used for certain time.

WHY /WHEN /WHERE AUTOFS?

If we want to save precious bandwidth & system resources then we should opt for autofs.

Still not clear…?

Let’s have an example,

Suppose you have a suitcase filled with imp file and docs, which are mandatory for you to carry all the times and you are a frequent traveller also and at after reaching at each destination you are supposed to edit some of your imp docs/files.

Hence my native place is A, and I need to frequently go to B…C…D…E…F…G. At all destinations you have a room booked on your name. Reached the room at “B”, open the suitcase, do your task edit and save the docs, pack the suitcase and move to “C” do the same and move on….

THAT’s It…!!!

Easy naa… what is the big deal in this…?

We all are doing same. Great… you caught it. We all are doing same,

Now let’s make it little technical.

Consider your native place “A” and all the rooms at destinations “B…C…D…E…F…G” as servers.

Your “Suitcase” as “HOME” directory on each servers.

The entire imp Files & Docs are saved at the home dir of your native place “A”.

Again … That’s it!!!

Now please show me how you will move with your suitcase from “A” to all the destinations and edit/save your imp docs.

Confused… LL

Here comes the “AUTOFS”

Actually what autofs will do is, it will mount your native home dir to all destinations wherever you go. Not only for “HOME” dirs, we can use it with any “NFS” mount. But this is most useful in case of “home” directories.

[root@rhel6-test1 ~]# rpm -qa |grep -i autofs

[root@rhel6-test1 ~]# yum install -y autofs*

Main config file is, /etc/auto.master è Here we specify the directories to be automounted and are monitored by “automount”.

To control global behavior of autofs, /etc/sysconfig/autofs

/etc/auto.master is default map. The auto_master map associates a directory with a map. It is a master list specifying all the maps that autofs should check.

Example,

+auto_master

/net            -hosts       è Special Map 

/home           auto_home    è Indirect Map   

/-              auto_direct  è Direct Map

SYNTAX: mount-point map-name [ mount-options ]

mount-point:

mount-point is the full (absolute) path name of a directory. If the directory does not exist, autofs creates it if possible. If the directory exists and is not empty, mounting on it hides its contents. In this case, autofs issues a warning.

The notation /- as a mount point indicates that the map in question is a direct map, and no particular mount point is associated with the map as a whole.

map-name:

map-name is the map autofs uses to find directions to locations, or mount information. If the name is preceded by a slash (/), autofs interprets the name as a local file. Otherwise, autofs searches for the mount information using the search specified in the name service switch configuration file (/etc/nsswitch.conf). Special maps are also used for /net

mount-options:

mount-options is an optional, comma-separated list of options that apply to the mounting of the entries specified in map-name, unless the entries in map-name list other options.

/net            -hosts       è Special Map 

Autofs mounts under the directory /net all the entries in the special map       -hosts. This is a built-in map that uses only the /etc/hosts database.

/home           auto_home    è Indirect Map   

An indirect map uses a substitution value of a key to establish the association between a mount point on the client and a directory on the server. Indirect maps are useful for accessing specific file systems, like home directories.

SYNTAX: key [ mount-options ] location

Key:

Key is a simple name (no slashes) in an indirect map.

Mount-options:

Mount-options is the options you want to apply to this particular mount. They are required only if they differ from the map default. Options for each specific type of file system are listed in the mount man page for that file system.

Location:

Location is the location of the file system, specified (one or more) as server:pathname.

/-              auto_direct  è Direct Map

The notation /- as a mount point indicates that the map in question is a direct map, and no particular mount point is associated with the map as a whole.

A direct map is an automount point. With a direct map, there is a direct association between a mount point on the client and a directory on the server. Direct maps have a full path name and indicate the relationship explicitly.

SYNTAX: key [ mount-options ] location

key:

key is the path name of the mount point in a direct map.

mount-options:

mount-options is the options you want to apply to this particular mount. They are required only if they differ from the map default.

location:

location is the location of the file system, specified (one or more) as server:pathname for NFS file systems or :devicename for High Sierra file systems (HSFS).

There is one very interesting share specified at “/etc/auto.master”.

SPECIAL MAP:

/net    -hosts

This share is always ready, provided both/several machines have entry in their “/etc/hosts” file.

I have 2 machines right now, “rhel6-server” & “rhel6-test1”, both have entries of each other in their /etc/hosts.

There are 2 shared directories on “rhel6-server”

[root@rhel6-server ~]# exportfs -v

/testnfs        <world>(rw,wdelay,root_squash,no_subtree_check)

/nfstest1       <world>(rw,wdelay,no_root_squash,no_subtree_check)  

These are not mounted anywhere, let’s check.

[root@rhel6-test1 /]# df -kh

Filesystem            Size  Used Avail Use% Mounted on

/dev/sda3              16G  6.3G  8.5G  43% /

tmpfs                 370M   76K  370M   1% /dev/shm

/dev/sda1             291M   37M  240M  14% /boot

/dev/sdb1             2.0G   85M  1.8G   5% /home

.host:/               108G   99G  8.5G  93% /mnt/hgfs

/dev/sr0              3.5G  3.5G     0 100% /media/RHEL_6.4 x86_64 Disc 1

And I want to access these directories from “rhel6-test1” without being mounted.

[root@rhel6-test1 net]# cd /net/rhel6-server

-bash: cd: /net/rhel6-server: No such file or directory

I am unable to access, Why…??

The directories are well shared by “rhel6-server”,

Service “nfs” is started on both servers. Let’s check for service “autofs”

[root@rhel6-server ~]# service autofs status

automount (pid  2778) is running...

[root@rhel6-test1 net]# service autofs status

automount is stopped

This was the problem, let’s start the service.

[root@rhel6-test1 net]# service autofs start

Loading autofs4:                                           [  OK  ]

Starting automount:                                        [  OK  ]

Now, check it again.

[root@rhel6-test1 net]# cd /net/rhel6-server

[root@rhel6-test1 rhel6-server]# ls -l

total 0

drwxr-xr-x. 2 root root 0 Jul 27 14:04 nfstest1

drwxr-xr-x. 2 root root 0 Jul 27 14:04 testnfs

[root@rhel6-test1 rhel6-server]# cd nfstest1

[root@rhel6-test1 nfstest1]# ls -ltr

total 0

-rw-r--r--. 1 root  root  0 May 22 17:20 f1

-rw-rw-r--. 1 raman raman 0 May 22 18:23 f2

-rw-r--r--. 1 root  root  0 May 23 18:33 f3

[root@rhel6-test1 nfstest1]# cd ../testnfs

[root@rhel6-test1 testnfs]# ls -l

total 8

-rw-r--r--. 1 nfsnobody nfsnobody    0 Apr 15 17:04 f2

-rw-rw-r--. 1 nfsnobody nfsnobody    0 Apr 15 16:55 r1

-rw-r--r--. 1 root      root         0 Apr 15 11:36 test1

drwxr-xr-x. 2 nfsnobody nfsnobody 4096 Apr 15 16:54 testdir

drwxr-xr-x. 2 nfsnobody nfsnobody 4096 Apr 15 17:01 testdir2

[root@rhel6-test1 testnfs]# touch testfile

[root@rhel6-test1 testnfs]# ls -l

total 8

-rw-r--r--. 1 nfsnobody nfsnobody    0 Apr 15 17:04 f2

-rw-rw-r--. 1 nfsnobody nfsnobody    0 Apr 15 16:55 r1

-rw-r--r--. 1 root      root         0 Apr 15 11:36 test1

drwxr-xr-x. 2 nfsnobody nfsnobody 4096 Apr 15 16:54 testdir

drwxr-xr-x. 2 nfsnobody nfsnobody 4096 Apr 15 17:01 testdir2

-rw-r--r--. 1 nfsnobody nfsnobody    0 Jul 27 14:12 testfile

[root@rhel6-test1 testnfs]# cd

[root@rhel6-test1 ~]# df -kh

Filesystem            Size  Used Avail Use% Mounted on

/dev/sda3              16G  6.3G  8.5G  43% /

tmpfs                 370M   76K  370M   1% /dev/shm

/dev/sda1             291M   37M  240M  14% /boot

/dev/sdb1             2.0G   85M  1.8G   5% /home

.host:/               108G   99G  8.5G  93% /mnt/hgfs

/dev/sr0              3.5G  3.5G     0 100% /media/RHEL_6.4 x86_64 Disc 1

192.168.234.206:/nfstest1

                       16G  2.9G   12G  20% /net/rhel6-server/nfstest1

192.168.234.205:/testnfs

                       16G  2.9G   12G  20% /net/rhel6-server/testnfs

Now, we can access all shared directories, shared at “rhel6-server”.

These directories are automatically mounted at “rhel6-test1”, just by providing

/net/<hostname>. Now I am out of these directories but still it is showing in o/p of “df –kh”.

Why…………??

There is idle timeout of 300 seconds/5M, after that it will be automatically unmount.

[root@rhel6-test1 ~]# df -kh

Filesystem            Size  Used Avail Use% Mounted on

/dev/sda3              16G  6.3G  8.5G  43% /

tmpfs                 370M   76K  370M   1% /dev/shm

/dev/sda1             291M   37M  240M  14% /boot

/dev/sdb1             2.0G   85M  1.8G   5% /home

.host:/               108G   99G  8.5G  93% /mnt/hgfs

/dev/sr0              3.5G  3.5G     0 100% /media/RHEL_6.4 x86_64 Disc 1

DIRECT MAP:

Let’s create a new share at “rhel6-server”.

[root@rhel6-server ~]# mkdir /autofs-test

[root@rhel6-server ~]# vi /etc/exports

#/testnfs *(rw,sync)

#/nfstest1 *(rw,sync,no_root_squash,no_all_squash)

/autofs-test *(rw,sync)

[root@rhel6-server ~]# export all

[root@rhel6-server ~]# exportfs -v

/testnfs        <world>(rw,wdelay,root_squash,no_subtree_check)

/nfstest1       <world>(rw,wdelay,no_root_squash,no_subtree_check)

[root@rhel6-server ~]# exportfs

/nfstest1       <world>

/testnfs        <world>

Still my new share is not showing,

[root@rhel6-server ~]# service nfs restart

[root@rhel6-server ~]# exportfs -v

/autofs-test    <world>(rw,wdelay,root_squash,no_subtree_check)

Now Good…

Let’s check this share at client server,

[root@rhel6-test1 ~]# showmount -e rhel6-server

Export list for rhel6-server:

/autofs-test *

Create a dir, on client to mount this shared dir.

AT AUTOMOUNT SERVER,

[root@rhel6-test1 ~]# mkdir /autofs-test-at_client

[root@rhel6-test1 ~]# chmod 777 /autofs-test-at_client

[root@rhel6-test1 ~]# mount -v rhel6-server:/autofs-test /autofs-test-at_client

mount: no type was given - I'll assume nfs because of the colon

mount.nfs: timeout set for Thu Jul 27 15:33:16 2017

mount.nfs: trying text-based options 'vers=4,addr=192.168.234.146,clientaddr=192.168.234.200'

rhel6-server:/autofs-test on /autofs-test-at_client type nfs (rw)

[root@rhel6-test1 ~]# df -kh

Filesystem            Size  Used Avail Use% Mounted on

/dev/sda3              16G  6.3G  8.5G  43% /

tmpfs                 370M   72K  370M   1% /dev/shm

/dev/sda1             291M   37M  240M  14% /boot

/dev/sdb1             2.0G   85M  1.8G   5% /home

.host:/               108G   99G  8.5G  93% /mnt/hgfs

rhel6-server:/autofs-test

                       16G  2.9G   12G  20% /autofs-test-at_client

Ok, now it is mounted. Let’s unmount it.

[root@rhel6-test1 ~]# umount /autofs-test-at_client

We have to do the same via “automount”.

Let’s start our “automount” configuration.

AT AUTOMOUNT CLIENT,

Here we are using “Direct Map” for the config,

[root@rhel6-test1 ~]# vi /etc/auto.master

/- /etc/auto.direct  ç added this line at end of file

[root@rhel6-test1 ~]# ls -l /etc/auto.direct

ls: cannot access /etc/auto.direct: No such file or directory

[root@rhel6-test1 ~]# vi /etc/auto.direct

/autofs-test-at_client  rhel6-server:/autofs-test ç added this entry

Here we can use, IP also instead of hostname.

[root@rhel6-test1 ~]# service autofs restart è Do this at Client & Server

Stopping automount:                                        [  OK  ]

Starting automount:                                        [  OK  ]

[root@rhel6-test1 /]# service autofs reload  è Do this at Client & Server

Reloading maps

[root@rhel6-test1 ~]# cd /autofs-test-at_client

[root@rhel6-test1 autofs-test-at_client]# ls -l

total 0

[root@rhel6-test1 autofs-test-at_client]# touch file1

[root@rhel6-test1 autofs-test-at_client]# ls -l

total 0

-rw-r--r--. 1 nfsnobody nfsnobody 0 Jul 27 16:23 file1

[root@rhel6-test1 autofs-test-at_client]# cd /

[root@rhel6-test1 /]# df -kh

Filesystem            Size  Used Avail Use% Mounted on

/dev/sda3              16G  6.3G  8.5G  43% /

tmpfs                 370M   72K  370M   1% /dev/shm

/dev/sda1             291M   37M  240M  14% /boot

/dev/sdb1             2.0G   85M  1.8G   5% /home

.host:/               108G   99G  8.5G  93% /mnt/hgfs

rhel6-server:/autofs-test

                       16G  2.9G   12G  20% /autofs-test-at_client

After 300S / 5M this will automatically unmount, we can control the umount time by editing “TIMEOUT=300” value at /etc/sysconfig/autofs.

Continued……