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daniels
Asked: 2015-10-31 05:37:23 +0800 CST

How to make /mnt/resource readable/writable but other users in Azure Linux VM?

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Right now /mnt/resource is owned by root and only root can read/write. How can I make this readable/writable by other users on the system?

And this should be persistent (i.e. after system restart it should still work)

linux

3 Answers

  1. How to make /mnt/resource readable/writable but other users in Azure Linux VM?

    To do this you need to use a command similar to the following:

    chown other_user /mnt/resource

    And this should be persistent (i.e. after system restart it should still work)

    Based on this documentation, the Azure Linux Agent (/usr/sbin/waagent) does the following:

    • Manages the resource disk

    • Formats and mounts the resource disk

    Upon provisioning an instance (starting/restarting) the device /dev/sdb1 will be mounted by waagent upon boot based on the setting ResourceDisk.MountPoint= in /etc/waagent.conf, defaulting to /mnt/resource. You can verify this by typing the command cat /var/log/waagent.log | grep sdb1 after stopping and starting an instance should show something like this:

    2016/06/17 09:06:42 Resource disk (/dev/sdb1) is mounted at /mnt/resource with fstype ext4

    Because waagent creates the mount some time after the boot, setting permissions immediately upon boot will not work. (I've experienced a race condition where I created a directory in /mnt/resource only to have it deleted when the mount occurs.)

    You can create a service which will wait until /dev/sdb1 is mounted to /mnt/resource/ then change permissions as needed.

    One way would be to have a script similar to the following run as an init script:

    #!/bin/sh

LOG=/tmp/startup.log
while [ `mount | grep /mnt/resource | wc -l` -lt 1 ];
do
    echo "Waiting for mount to be created by waagent..." >> ${LOG}
    sleep 5
done
echo "Changing /mnt/resource permissions..." >> ${LOG}
chown other_user /mnt/resource
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  2. Chown and Chmod are the commands to achieve this.

    Probably easier just to read this https://en.wikipedia.org/wiki/Chmod

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  3. /mnt/resource WILL NOT PERSIST no matter what you do with it Documentation

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