NFS root unexpectedly squashed

While experimenting with setting up ltsp on Fedora 18, I came across a strange NFS behaviour which took quite some time to iron out.

I was already exporting /opt as a read only file system; however, with root squashed. LTSP added another export for /opt/ltsp with no_root_squash option. 

/opt *(ro,sync,no_subtree_check)
# export for LTSP version 5
/opt/ltsp   *(ro,no_root_squash,async,no_subtree_check)

Everything seemed to be sort of working with a few strange effects, e.g. I could not use passwords and some ltsp scripts were failing.
The problem was that root seemed to be still squashed:

[anil@localhost ~]$ sudo mount amd:/opt/ltsp/x86_64 /mnt
[anil@localhost ~]$ cd /mnt/home
[anil@localhost home]$ ls -l
total 8
drwxrwx--- 2 anil  anil  4096 Apr  6 13:04 anil
drwx------ 2 guest guest 4096 Apr 10 12:35 guest
[anil@localhost home]$ sudo su
[root@localhost home]# cd anil
bash: cd: anil: Permission denied

A workaround was to use fsid=0 although whatever documentation I came across seemed to suggest that it was no longer needed:

/opt/ltsp   *(ro,fsid=0,no_root_squash,sync,no_subtree_check)

Unfortunately, I had forgotten that /opt was also being exported and noticed it only after finding the work-around and getting ltsp to work on Fedora 18.

Booting Porteus over the LAN from Fedora 18 server

Continuing my experiments with diskless options, I was going through RAM resident distributions on Wikipedia. Porteus appealed to me as it was able to run KDE desktop from RAM. The newly released version is packaged to boot off the network from a Porteus system with no additional effort.

I wanted to boot from my existing Fedora 18 system and I wanted to avoid using tftp. The recipe I used is as follows:

In order to make sure that both tftp and html could be used:

$ sudo ln -s /var/lib/tftpboot /var/www/html/tftpboot

Obviously, httpd and dhcpd are enabled. There is no need to enable tftp in /etc/xinetd.d/tftp. The following steps were needed in the tftpboot directory:

$ sudo mount -o loop Downloads/Porteus-v2.0-x86_64.iso /mnt
$ sudo mkdir /var/lib/tftpboot/porteus
$ sudo cp -r /mnt/boot/syslinux/* /var/lib/tftpboot/porteus

Now, we need to edit /etc/dhcp/dhcpd.conf. It's content (for my network) will be:

# dhcpd.conf
#
# configuration for pxe from http://docs.fedoraproject.org/en-US/Fedora/17/html/Installation_Guide/s1-netboot-pxe-config.html
#
  option space pxelinux;
  option domain-name-servers 192.168.1.1, 8.8.8.8;
  option pxelinux.magic code 208 = string;
  option pxelinux.configfile code 209 = text;
  option pxelinux.pathprefix code 210  = text;
  option pxelinux.reboottime code 211 = unsigned integer 32;

  subnet 192.168.2.0 netmask 255.255.255.0 {
          option routers 192.168.2.1;
          range 192.168.2.200 192.168.2.210;

          class "pxeclients" {
                  match if substring (option vendor-class-identifier, 0, 9) = "PXEClient";
                  next-server 192.168.2.1;
                  option pxelinux.pathprefix "http://192.168.2.1/tftpboot/porteus/";
                  filename "http://192.168.2.1/tftpboot/porteus/pxelinux.0";
          }
  }

 Finally, we need to copy the base os files into the http root, i.e.

$ sudo cp /mnt/porteus/base/* /var/www/html

We need to disable the welcome screen for Porteus to successfully boot from the apache server. So, comment all lines in
/etc/httpd/conf.d/welcome.conf.

Now, restart the httpd and dhcpd servers.

On the client machine, I am using grub2. The client is configured as follows:

1. Download ipxe.iso
2. Extract ipxe.krn from the iso and copy it in /boot of the client.
3. Edit /etc/grub.d/40_custom and add the following lines:
   menuentry "ipxe"{
         linux16 /boot/ipxe.krn
   }
4. Create a new grub.cfg
   Fedora:  /boot/grub2/grub.cfg using grub2-mkconfig
   Ubuntu: /boot/grub/grub.cfg using grub-mkconfig

Reboot the client. Choosing the ipxe option should bring up the Porteus boot menu and it should boot into kde or lxde depending upon the option selected.