[LONG] Maintaining several identical installations of (B)LFS
Alexander E. Patrakov
semzx at newmail.ru
Wed Jul 30 06:58:17 PDT 2003
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
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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