[LONG] Maintaining several identical installations of (B)LFS

Alexander E. Patrakov semzx at newmail.ru
Wed Jul 30 06:58:17 PDT 2003


Hi all,
the problem is as follows. In the classroom, we have 15 computers which must 
have both Windows 2000 (maybe we'll move to XP) and Linux (of course, from 
scratch). While maintaining Windows installation is not among my duties, I 
have to ensure that the installations of Linux are good and as identical as 
possible (there are some hardware differences).

In the previous year, this problem was addressed by using a NFS-root 
installation of LFS. We used modified Etherboot as a bootloader, so there was 
even no need for non-NTFS partitions on workstations. All per-machine 
configuration was handled by a special script that mounted (--bind) 
machine-specific directories under /etc/local, /var and /tmp. DHCP was 
configured in such a way that n-th machine from the door always gets the 
address 192.168.1.(n+20), so these per-machine directories are always the 
same. I will mail the script upon request.

That approach made the administration extremely simple (much simpler than in 
Windows with Norton Ghost): do something on one computer, and others will 
benefit from it immediately. But it had a drawback: either the network speed 
or the speed of the hard drive on the NFS server is an important limiting 
factor, which manifests itself starting with 7-10 clients. The NFS server is 
a rather old Pentium and it does not run LFS. I am not sure that I will be 
allowed to move the NFS server onto a new LFS box, which is currently acting 
as a web and mail server.

Hdparm reports that the disk has speed 20 MB/s on the old server. Since we use 
Promise ATA RAID (mirroring) on the new server, hdparm cannot be used as a 
benchmark. It is known that a single drive of the same model gives 38 MB/s. I 
think that those figures say nothing: seeks are probably the real bottleneck.

Also, we are probably unable to use the full speed of our network. The HUB 
(sorry, nobody is going to buy a switch) indicates the network utilization of 
30% (i.e. 30 Mbit/s) dufing dd if=/dev/zero of=/some/file/on/nfs (other 
clients are typing something in OpenOffice). The old server and 50% of the 
clients has 3c905 as a network card. Other 50% of the clients and a new 
server have Intel EtherExpress 100 and complain about downgrading to 
half-duplex. During the high load, there are occasional messages of duplex 
mismatch also from 3c905 driver.

While I have some time, I want to investigate some alternatives to our 
NFS-root installation. It is probably possible to add another Pentium 2 400 
as a second NFS server, and maybe a Pentium 4 2.4 (the current web server) 
may also do something if my boss will allow that. Variants involving load 
balancing between two NFS servers will be considered if there are means of 
easy software updates without the risk of ending up with different contents 
of two servers. Non-NFS-root variants allowing easy updates will also be 
considered.

So I would like to know what is used by you for similar tasks (keeping several 
installations of BLFS identical).

Also: do we need to continuously mount home directories from an NFS server in 
the case of a non-NFS-root installation? Windows admins tell me (without 
meaningful explanation) to find a way to copy a use's home directory onto a 
hard disk entirely upon login and copy it back upon logout.

-- 
Alexander E. Patrakov




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