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Autofs – автомонтирование

Autofs

Autofs - это программа, позволяющая монтировать внешние устройства по требованию. Другие способы монтирования могут быть выполнены с помощью ручной команды для временного монтирования или с помощью файла /etc/fstab, если Вы хотите монтировать устройство постоянно.

Autofs можно использовать для монтирования:

USB-flash-дисков
внешних жестких дисков
сетевых устройств хранения данных
CD-ROM / DVD / BlueRay и так далее.

Autofs монтирует эти устройства в локальные каталоги. Когда Вы захотите, или программа, которую Вы используете, захочет прочитать с устройства или записать на него, autofs сделает это из этих локальных каталогов. Если Вы много работаете с монтированными системами - Вам определенно понравится данный механизм.

Некоторые люди считают, что поскольку autofs не поддерживается на должном уровне - он не будет существовать долго, но подумайте об этом: зачем поддерживать программу, которая уже делает то, что должна делать?

Другой способ монтирования "на лету" описан на этой странице вики: Fstab - использование автомонтирования SystemD

Установка

На момент написания статьи номер версии autofs был 5.1.3-1. Он может быть установлен из стандартных репозиториев Manjaro с помощью Octopi, Pamac или Pacman. Если Вы хотите использовать autofs с nfs, то Вам понадобится дополнительный пакет - nfs-utils. Поэтому установите и его. В описании он называется: Support programs for Network File Systems

Тестирование монтирования

Перед установкой и настройкой autofs неплохо бы проверить можете ли Вы подключить устройство, которое хотите смонтировать.

Давайте сначала выясним, что Вы хотите монтировать. В пакете nfs-utils есть хорошая команда для этого: showmount:

showmount -e 192.168.1.9

Когда устройство включено - в выводе будет что-то вроде:

Export list for 192.168.1.9: /HDD1 *

There is a disk called HDD1 in the device on address 192.168.1.9.

Remark: You do need to know the IP-address of the device to use showmount.

Now let’s mount it to our local folder /mnt:

‘’’sudo mount -t nfs 192.168.1.9:/HDD1 /mnt’’’

Type ‘ls /mnt’ to find out what is on the disk you just mounted. When you see contents the mount has succeeded and we can now continue with the configuration of autofs.

Terminal commands

Commands you can use are:

sudo systemctl enable autofs Command to enable autofs so it can be started either manually or at next boot

sudo systemctl start autofs Command to manually start autofs

sudo systemctl restart autofs Command to manually restart autofs

sudo systemctl stop autofs Command to manually stop autofs

sudo systemctl status autofs Command to read the status of autofs

When autofs is running this is the output of the status command:

sudo systemctl status autofs

 ● autofs.service - Automounts filesystems on demand
    Loaded: loaded (/usr/lib/systemd/system/autofs.service; enabled; vendor preset: disabled)
    Active: active (running) since Sat 2017-12-02 07:13:22 CET; 1h 9min ago
   Process: 1069 ExecStart=/usr/bin/automount $OPTIONS --pid-file /run/autofs.pid (code=exited, status=0/SUCCESS)
  Main PID: 1089 (automount)
     Tasks: 5 (limit: 4915)
    CGroup: /system.slice/autofs.service
            └─1089 /usr/bin/automount --pid-file /run/autofs.pid
 Dec 02 07:13:22 Desktop-Jan systemd[1]: Starting Automounts filesystems on demand...
 Dec 02 07:13:22 Desktop-Jan automount[1089]: -
 Dec 02 07:13:22 Desktop-Jan systemd[1]: Started Automounts filesystems on demand.

After a stop it looks like this:

sudo systemctl status autofs

 ● autofs.service - Automounts filesystems on demand
    Loaded: loaded (/usr/lib/systemd/system/autofs.service; enabled; vendor preset: disabled)
    Active: inactive (dead) since Sat 2017-12-02 08:27:27 CET; 1s ago
   Process: 1069 ExecStart=/usr/bin/automount $OPTIONS --pid-file /run/autofs.pid (code=exited, status=0/SUCCESS)
  Main PID: 1089 (code=exited, status=0/SUCCESS)
 Dec 02 07:13:22 Desktop-Jan systemd[1]: Starting Automounts filesystems on demand...
 Dec 02 07:13:22 Desktop-Jan automount[1089]: -
 Dec 02 07:13:22 Desktop-Jan systemd[1]: Started Automounts filesystems on demand.
 Dec 02 08:27:26 Desktop-Jan systemd[1]: Stopping Automounts filesystems on demand...
 Dec 02 08:27:27 Desktop-Jan systemd[1]: Stopped Automounts filesystems on demand.

Configuration

After installation we need to configure a few files specific to what we need and want. These files are placed in the folder: /etc/autofs. In fact there are 2 files needed: auto.master and auto.<any name you like>. Since /etc/autofs is a folder owned by root you need root privileges to write and/or edit them.

In auto.master we write:

the base folder where mounts are connected to the local filesystem
the name of the file in which the mount can be configured
a timeout value (time after which the mount is automatically unmounted when not needed anymore)
ghost, an option which places empty folders in the base folder to make it possible, after the time-out, to mount the device again.

A typical line in the auto.master file can look like this:

/mnt /etc/autofs/auto.NAS1 --timeout=10 --ghost

When you have more than one external device you want to mount using autofs you can do 2 things:

write an extra line in the auto.master file for each device. For example:

/mnt /etc/autofs/auto.NAS1 --timeout=10 --ghost

/mnt /etc/autofs/auto.NAS2 --timeout=10 --ghost

and create extra config files for each device, or

use 1 line in the auto.master file using 1 config file for all devices and write more than 1 line in this config file. This is totally up to you.

I use this:

/etc/autofs/auto.master:

/mnt /etc/autofs/auto.shares --time-out=5 --ghost

/etc/autofs/auto.shares:

NAS-Seagate -fstype=nfs,rw,soft,retry=0 Seagate:/shares/Folder1

NAS-WD -fstype=nfs,rw,soft,retry=0 WD:/nfs/Public

This way I have one master file which, with one line, controls the base of the system and one file which controls all my shares. But again, this is totally up to you.

Explanation of auto.master

This file is created when you install the autofs package. You will need to edit it to make it work for you. The complete file looks like this when created:

key [ -mount-options-separated-by-comma ] location

 # For details of the format look at autofs(5).
 #
 #/misc	/etc/auto.misc
 #
 # NOTE: mounts done from a hosts map will be mounted with the
 #	"nosuid" and "nodev" options unless the "suid" and "dev"
 #	options are explicitly given.
 #
 #/net	-hosts
 #
 # Include central master map if it can be found using
 # nsswitch sources.
 #
 # Note that if there are entries for /net or /misc (as
 # above) in the included master map any keys that are the
 # same will not be seen as the first read key seen takes
 # precedence.
 #
 #/net        -hosts           -nosuid
 +auto.master

Add your line or lines just before the last visible line: +auto.master

After that line an empty line should exist or the configuration will not succeed, so place the cursor after +auto.master and click on ENTER.

Format of the line you add:

base-folder name_of_share_file options.

In my example this is:

/mnt /etc/autofs/auto.shares --time-out=5 --ghost

NOTE: Make sure the used filename in the auto.master file should be exactly the same as the name of the file you use, including the path.

The base folder can be /. In this case it is written as: /- You use direct addressing now. The address you write in the shares file (see next paragraph) becomes the complete address. When you write the name of a folder in the master file you use indirect addressing: the complete path is now the sum of the path in the master file + the one in the shares file.

Explanation of auto.shares

This file can have any extention name you like. Make it a descriptive one to easily find it, especially when you use more than one. The line or lines in this file are all built according to this template:

name_of_sub-folder options source

(separated with at least one space)

After mounting the external device can be found in the following directory structure:

/base-folder/sub-folder

You define the base folder in the auto.master file (first item in the line) and the sub-folder is defined in the auto.xxxx file (also first item on the line)

My shares are mounted at: /mnt/NAS-WD and /mnt/NAS-Seagate.

/mnt is the base-folder (from auto.master) and both NAS folders are written in the shares file.

Options you can use are plenty. See the man pages for autofs, automount and nfs. The ones I used here work for me. They take care of the following:

-fstype=nfs

The used filesystem is nfs (Network File System), a file-system used much in Linux environments.

rw

The mount is readable and writable. If you only need read access then use ro (read only)

soft

If the server fails an I/O error is given, but the file-manager keeps running. When you use hard instead of soft, it hangs till the connection has been re-established.

retry=0

This makes sure that mount stops immediately when the server is not reachable. If not, mount will keep trying for 2 minutes to reach the server and block the program which wants to reach the server.

Remarks

It is said that when you make a change in the shares file, the change will be active straight away. When changing the master file you need to restart the autofs.service like this:

sudo systemctl restart autofs It is advisable to also restart after changing the shares file, just to be sure.

The permissions of both the master and the share file(s) should be 644. That means Read/Write permission for user, Read for group and Read for others.

Test if the system works. First example is the result when nothing is mounted, in the second example you see the result when the NAS-WD is mounted:

$ /etc/autofs > sudo ps -A|grep "nfs\|rpc"

240 ? 00:00:00 rpcbind

 23222 ?       00:00:00 rpciod
 23227 ?       00:00:00 nfsiod

$ /etc/autofs > cd /mnt/NAS-WD Change directory to the mount

$ /mnt/NAS-WD > sudo ps -A|grep "nfs\|rpc"