Thanks for the explanation. I understood your point. > -----Original Message----- > From: Bernd Petrovitsch [mailto:be...@firmix.at] > Sent: 08 September 2009 16:38 > To: Vivek Subbarao > Cc: kernelnewbies@nl.linux.org > Subject: Re: Ip address assignment > > On Tue, 2009-09-08 at 01:10 -0700, Vivek Subbarao wrote: > [...] > > The ip address assigned through ifconfig is not persistent. Why is > the > > behaviour so? Instead of editing files to add persistent addresses > why > > not make ifconfig add persistent addresses? Is there a drawback to > > this? > - It's not the kernels job to persistently store this or that data > item. > Period. > IP addresses may be configured by hand (if you install a machine the > first time), statically but also come through BOOTP, DHCP (or > whatever > protocol or system in the future). > The above is decided by the admin and it's the most simple way to do > it there (and have in the kernel just some sys-calls to configure > that). > - Even if: consider the implications (or at least the first few that > come to my mind): > a) > * Kernel boots > * Kernel wants to load data from the persistent storage. > That implies that the persistent storage (e.g. file in local > filesystem on whatever hardware, file in remote filesystem, raw in > NVRAM or similar, over ethernet/USB/SATA/IDE/SCSI/SAS/...). > See the contents of /etc/rc.d on CentOS-5.3 for all of the script > logic which is used now to bring up your host. A good part of it (if > not all) should be copied into the kernel? > Basically you get a *lot* of code and complexity into the kernel > which > is already present (and must be also dealt with) in user-space > anyways > (usually by the SysV-Init and around provided by $distribution). > What to do in case of an error/problem (let alone development and > testing)? > - Boot without that data: That may work for IP addresses but not for > many other "persistent kernel data". > And where are we then? Just like today. > b) How do you backup and recover(!) that data seriously (and for lots > of machines)? > Add some special filesystem to export it as file(s)? > If yes: Where is the real difference to today? > c) And you actually want the possibility to try stuff without any > immediate persistent storage (e.g. configuring a firewall on the > other side of the planet over ssh. You schedule a reboot in 5-10 > minutes and load the new rule set. If the new rule set works, you > cancel the reboot and copy the new rule set over the really used > one. If it doesn't work - and you just cut the ssh connection -, > you just wait for the reboot to happen and fix it up). > So you need at least one additional flag everywhere for > "persistent > or not". > > Bernd > > PS: In case you didn't realize it: The "registry" in the Windows-NT-and > newer world was a nice try but doesn't solve more problems than it > adds. > -- > Firmix Software GmbH http://www.firmix.at/ > mobil: +43 664 4416156 fax: +43 1 7890849-55 > Embedded Linux Development and Services >
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