#nfs4

it felt pretty nice to do

It was bound to happen eventually, I had to dive into how NFS4 really works, not just rely on miracles.

In NFSv4 client and server exchange user names and group names in textual form not UID/GID numbers. So they must share some database about how to map users/groups to UID/GID (this database is called /etc/passwd and /etc/group). And also they must share the nfs domain. If you run a mostly homogeneous server environment, chances are things just work.

Now in a proper setup, you’d choose NIS for this task, a network server that provides mapping to clients and servers. I did not want to introduce another moving part, so the other option are “local files” on the Data Movers.

There’s very little documentation about how to actually do this. Or shall we say, there’s so much documentation that it’s hard to find what you need to do.

I did not find a way to do this in EMC Unisphere interface. So ssh to your control station and first set the nfs domain:

$ server_param server_2 -facility nfsv4 -list

Set the domain. I just kept using “localdomain” because all servers already have this one setup and it’s now likely I’ll move to NIS.

$ server_param server_2 -facility nfsv4 -modify domain -value localdomain

No reboot required. (Nice)

Note: You can actually change the domain variable in Unisphere, but’s ridiculously hidden.

Second task is to create the needed users and groups. Remember, you need user and group entries of all used names. So if you want to use this NFS share as a backup location where you rsync things, you’re probably better off using NFSv3.

I found ways to add users, only one way to add groups. So to add a user you can do this:

server_user server_2 -list

server_user server_2 -add www-data

User ID: 33 Group ID: 33 Comment: Home directory: Shell:

server_user server_2 -list

The second way is to “download” the password and group files from DM servers, change them and put them back:

server_file server_2 -get passwd passwd

server_file server_2 -get group group

If you edit (vi) you passwd file, you’ll see something like this:

www-data:!!:33:33:::

Edit your group file to add the needed group lines:

www-data:x:33:

Now send the files back up to your DM:

server_file server_2 -put passwd passwd

server_file server_2 -put group group

There, chwon start to work instantly.

Resolved: Secure Network Filesystems for Linux: What are people doing? #development #fix #it

Secure Network Filesystems for Linux: What are people doing?

NFSv3 is widespread, but the default security model is… quaint. CIFS can use Kerberos authentication, but without POSIX semantics it’s a non-starter. AFS never did encrypt traffic on the wire and is krb4 — and basically a dead project. Fancy new experimental filesystems either never materialize or are focused on speed (and if you’re…

Resolved: Understanding NFS4 (Linux server) #programming #computers #dev

Understanding NFS4 (Linux server)

I’ve been a bit bothered by NFS4 on Linux. Some information ‘out there’ seems to conflict with other information, and other information appears hard to find. So here are a couple of things that caught my attention, hopefully someone out there can shed some light on this.

This question focuses exclusively on NFS4 without Kerberos etc.

1. Exports

There is…

How to: NFS v3 versus v4 #programming #solution #dev

NFS v3 versus v4

I am wondering why NFS v4 would be so much faster than NFS v3 and if there are any parameters on v3 that could be tweaked.

I mount a file system

sudo mount -o 'rw,bg,hard,nointr,rsize=1048576,wsize=1048576,vers=4' toto:/test /test

and then run

dd if=/test/file of=/dev/null bs=1024k

I can read 200-400MB/s but when I change version to vers=3, remount and rerun the dd I only get