NFS

From regional-training

Sick of network mounts that fail and grip your VMs? Then you can follow these tips:

nfs-client or cif-client

Particularly useful for Remote filesystem or detachable drives, you really on want them mounted upon access, so what you want to do is use the noauto,x-systemd.automount parameters. In addition, you can use the x-systemd.mount-timeout= option to specify how long systemd should wait for the mount command to finish. Also, the _netdev option ensures systemd understands when that the mount is network dependent and order it after the network is online.

  • include these options instead of default on your /etc/fstab
noauto,x-systemd.automount,x-systemd.mount-timeout=30,_netdev
  • also include as appropriate
,rw,suid,dev,exec,nouser,async

now to stop your nfs-server crashing on a bad export

If you have an invalid line in /etc/exports then by default your nfs-server will not start 

# cat /etc/exports
/virtual/shared		192.168.122.0/24(rw,no_root_squash,subtree_check)
/mnt/SSD	        192.168.122.0/24(rw,no_root_squash,subtree_check)
/mnt/junk	        192.168.122.0/24(rw,no_root_squash,subtree_check)
  • so this will fail
systemctl restart nfs-server; systemctl status nfs-server

● nfs-server.service - NFS server and services
   Loaded: loaded (/lib/systemd/system/nfs-server.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Wed 2020-07-29 15:45:36 AEST; 1min 4s ago
  Process: 23060 ExecStartPre=/usr/sbin/exportfs -r (code=exited, status=1/FAILURE)
  Process: 23061 ExecStopPost=/usr/sbin/exportfs -au (code=exited, status=0/SUCCESS)
  Process: 23062 ExecStopPost=/usr/sbin/exportfs -f (code=exited, status=0/SUCCESS)

Jul 29 15:45:36 c3po2 systemd[1]: Starting NFS server and services...
Jul 29 15:45:36 c3po2 exportfs[23060]: exportfs: Failed to stat /mnt/junk: No such file or directory
Jul 29 15:45:36 c3po2 systemd[1]: nfs-server.service: Control process exited, code=exited, status=1/FAILURE
Jul 29 15:45:36 c3po2 systemd[1]: nfs-server.service: Failed with result 'exit-code'.
Jul 29 15:45:36 c3po2 systemd[1]: Stopped NFS server and services.

On Debian the nfs-server definition is deployed here: 

 /lib/systemd/system/nfs-server.service

Since systemd it is a simple matter of ignoring return codes from commands by prefixing the command with a - in the service definition: 

[Unit]
Description=NFS server and services
DefaultDependencies=no
Requires=network.target proc-fs-nfsd.mount
Requires=nfs-mountd.service
Wants=rpcbind.socket
Wants=nfs-idmapd.service

After=local-fs.target
After=network.target proc-fs-nfsd.mount rpcbind.socket nfs-mountd.service
After=nfs-idmapd.service rpc-statd.service
Before=rpc-statd-notify.service

# GSS services dependencies and ordering
Wants=auth-rpcgss-module.service
After=rpc-gssd.service gssproxy.service rpc-svcgssd.service

# start/stop server before/after client
Before=remote-fs-pre.target

Wants=nfs-config.service
After=nfs-config.service

[Service]
EnvironmentFile=-/run/sysconfig/nfs-utils

Type=oneshotq
RemainAfterExit=yes
ExecStartPre=/usr/sbin/exportfs -r
ExecStart=/usr/sbin/rpc.nfsd $RPCNFSDARGS
ExecStop=/usr/sbin/rpc.nfsd 0
ExecStopPost=/usr/sbin/exportfs -au
ExecStopPost=/usr/sbin/exportfs -f

ExecReload=/usr/sbin/exportfs -r

[Install]
WantedBy=multi-user.target
  • So I made the following changes and now my nfs-server survives a bad export definition in the /etc/exports file!
ExecStartPre=-/usr/sbin/exportfs -r
ExecStopPost=-/usr/sbin/exportfs -au
ExecStopPost=-/usr/sbin/exportfs -f
ExecReload=-/usr/sbin/exportfs -r
  • restart and view status
systemctl restart nfs-server; systemctl status nfs-server
  • and it no longer fails to start
sudo systemctl status nfs-server

● nfs-server.service - NFS server and services
   Loaded: loaded (/lib/systemd/system/nfs-server.service; enabled; vendor preset: enabled)
   Active: active (exited) since Wed 2020-07-29 15:47:15 AEST; 16min ago
  Process: 23252 ExecStartPre=/usr/sbin/exportfs -r (code=exited, status=1/FAILURE)
  Process: 23253 ExecStart=/usr/sbin/rpc.nfsd $RPCNFSDARGS (code=exited, status=0/SUCCESS)
 Main PID: 23253 (code=exited, status=0/SUCCESS)

Jul 29 15:47:15 c3po2 systemd[1]: Starting NFS server and services...
Jul 29 15:47:15 c3po2 exportfs[23252]: exportfs: Failed to stat /mnt/junk: No such file or directory
Jul 29 15:47:15 c3po2 systemd[1]: Started NFS server and services.

samba or cifs mounts

  • the package cifs-utils should be installed instead of smbfs.
apt install cifs-utils
  • mount via:
mount -t cifs //FILE-SERVER-IP-ADDRESS/public /local/mountpoint -o user=nobody

You will be asked for a password. Confirm the password by pressing the Enter key. The share should now be mounted and ready for reading and writing.

how to move a system mount or folder

So you have a /var mount and it is in a Logical Volume on some Volume Group and you want to move it into another location e.g. into another LVM or part of the file system, what do you do?


Visit existing filesystem if moving to an existing file system, else these other instruction you are dealing with moving to a new Logical Volume.

onto existing file system target

  • change to root
su -
  • make a folder on the target file system (which might be in a new Logical Volume see #moving to new LV)
mkdir /var.new
  • copy the old /var contents over to /newvar
cp -a /var/* /newvar/
  • rename the old /var
mv /var /var.old
  • rename the /var.new
mv /var.new /var
  • verify (there should only be /var/log changes, unless you have prior moved /var/log off via a mount or link)
diff -r /var.new /var
  • important fix the fstab
cp /etc/fstab /etc/fstab.date
  • now edit /etc/fstab and fix up your mount
vi /etc/fstab
  • check that you can mount it
umount /var
mount /var
ls -lrta /var
  • double check rest of fstab
mount -a
  • make sure you have no errors otherwise the OS will not reboot

You are done, you may reboot.

moving to new LV

You are here because you want to move /var from a VG Logical Volume to another.

  • change to root
su -
  • make a new Logical Volume for /var
lvcreate -L 2G -n var /dev/vg
  • place a file system on it
mkfs.ext4 /dev/vg/var
  • mount the new LV
mkdir /mnt/tmp
mount /dev/vg/var /mnt/tmp
  • copy the /var over to new LV /var directory
cp -a /var /mnt/tmp
  • rename the old /var
mv /var /var.old
  • umount the temporary acces
umount /mnt/tmp
rmdir /mnt/tmp
  • test mount the new LVM
mount /dev/vg/var /var
  • fix up fstab
vi /etc/fstab
  • test that you have no errors
mount -a
  • make sure you have no errors otherwise the OS will not reboot


You are done, you may reboot.

Refer to this https://snott.net/linux/how-to-move-a-system-folder-into-a-newly-created-lvm/

re-mount eject USB

  • eject
eject /dev/sdX
  • remount
eject -t /dev/sdX

hints

  • How to tell where something is mounted?
df <path>

categories

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