[lustre-discuss] [EXTERNAL] mdt and mgt are always in RO mode

[Andreas Dilger]

You need to mount a client in order to access the filesystem storage, either on the same node or on a different node.

The /mnt/mdt and /mnt/ost directories are only for running "df" and passing ioctl commands down to the underlying filesystem (fstrim and resize2fs).  You cannot access any files or data there.  Just like  you cannot create a file on /dev/sda1 when an ext4 filesystem is formatted there, you need to mount the filesystem and create the files/directories in the mountpoint.

Cheers, Andreas

On Aug 5, 2025, at 22:43, Ran Mo via lustre-discuss <lustre-discuss at lists.lustre.org> wrote:

Thanks Rick a lot. You save me from keeping reinstalling Lustre/troubleshooting why it is in RO. :)

Sorry, I am new to Lustre. I am trying to setup and test two functions below.
1) Use Lustre's identity feature to create users on the client side, and require user to be authenticated at Lustre server n before allowing them to access the file system.
2) Enable the nodemap feature to enforce user data isolation; Create Tenant A and Tenant B, and ensure that each tenant can only mount and see data within their respective subdirectories of the file system.

For test 1), per research , looks like there is a need to install Lustre_id at client side but I just cannot find it.
For test 2), per research , ChatGPT asked me to create two sub directories (for examples, mkdir /mnt/mdt/{tenantA,tenantB}) under mount point of MDT (/mnt/mdt) on MDS server but since it is RO mode, I am not allowed to do so. That's where I have been stuck for test 2). (:

Not sure if you can share your ideas on these.

Environment:
3 Rocky8.10 VMs (MDS+MGS on server1, the other two are OSS). Two Ubuntu VMs (22.04) as client. All is running Lustre 2.15.7.

Thanks again.
Ran

________________________________
From: Mohr, Rick <mohrrf at ornl.gov>
Sent: Wednesday, August 6, 2025 2:16 AM
To: Ran Mo <HenryMo2012 at outlook.com>; lustre-discuss at lists.lustre.org <lustre-discuss at lists.lustre.org>
Subject: Re: [EXTERNAL] [lustre-discuss] mdt and mgt are always in RO mode

Ran,

This is normal.  The MGTs/MDTs/OSTs will always show up as read-only in the output from the "mount" command, even when the lustre file system is writable.

--Rick



On 8/5/25, 1:15 PM, "lustre-discuss on behalf of Ran Mo via lustre-discuss" <lustre-discuss-bounces at lists.lustre.org <mailto:lustre-discuss-bounces at lists.lustre.org> on behalf of lustre-discuss at lists.lustre.org <mailto:lustre-discuss at lists.lustre.org>> wrote:


Greenings,

I tried installed Lustre many time (both 2.15.6 and 2.15.7) but mdt and mgt are always under read only mode.
=====
[root at mds_node ~]# mount | grep nvme
/dev/nvme0n1p1 on /boot type xfs (rw,relatime,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/nvme0n2 on /mnt/mgt type lustre (ro,svname=MGS,nosvc,mgs,osd=osd-ldiskfs,user_xattr,errors=remount-ro)
/dev/nvme0n3 on /mnt/mdt type lustre (ro,svname=lustrefs-MDT0000,mgsnode=192.168.31.20 at tcp0:192.168.31.20 at tcp,osd=osd-ldiskfs,user_xattr,errors=remount-ro,_netdev)
[root at mds_node ~]#

I tried umount and mount and other methods, but unfortunately, cannot get it into RW mode.

Can you give me a hint please? Thanks,

Ran



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Cheers, Andreas
—
Andreas Dilger
Lustre Principal Architect
Whamcloud/DDN




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