Hi LeVA, > I have two disk drives, and each of them has a swap partition. I would > like to swap to both of them, but firstly to the "other" disk, which is > not used during the running of the system, thus making the swapping > less painful (the drives are on separate ide channels/cables). > > The swap partition which is on the disk which has the root partition > gets always priority 0, so I thought that I should add this to my > fstab: > > /dev/wd1b none swap sw,priority=0 0 0 > /dev/wd0b none swap sw,priority=1 0 0 > > But after reboot, both of the swap partitions gets priority 0. > I can change the wd0b's priority to 1 after the boot, but is this the > proper way of doing this, and one can not define the main swap > partition's priority in fstab?
On bootup, swap configuration using fstab(5) is done by swapctl(8) from rc(8). But, as far as i have seen on 3.9-stable and earlier systems, the GENERIC kernel adds the "b" partition of the root disk as a swap partition even before spawning init(8), i.e. long before /sbin/init can invoke /etc/rc, at least if that partition looks like a swap partition. Thus, when /etc/rc gets to the line `swapctl -A -t blk`, the swap partition is already active. You can verify this assertion by commenting out *all* swap lines from /etc/fstab, rebooting and typing [EMAIL PROTECTED] $ swapctl -l Device 512-blocks Used Avail Capacity Priority swap_device 524160 241544 282616 46% 0 (Er, well, i *really* ought to get more RAM for idefix, it is not that expensive any more.) You see that the swap device is quoted as "swap_device". As far as i understand, that's what the kernel will call it if it was activated during kernel booting, before spawning /sbin/init. Now, if a swap device is already active, `swapctl -a -p` does not change its priority, only `swapctl -a -c` does so: [EMAIL PROTECTED] # swapctl -l Device 512-blocks Used Avail Capacity Priority swap_device 524160 246088 278072 47% 0 [EMAIL PROTECTED] # swapctl -a -p 1 /dev/wd0b [EMAIL PROTECTED] # swapctl -l Device 512-blocks Used Avail Capacity Priority swap_device 524160 246088 278072 47% 0 [EMAIL PROTECTED] # swapctl -c -p 1 /dev/wd0b [EMAIL PROTECTED] # swapctl -l Device 512-blocks Used Avail Capacity Priority swap_device 524160 246088 278072 47% 1 This is perhaps not perfectly documented in the man pages - one might add "If _arg_ is already enabled, nothing is changed, in particular not the priority" after "If cmd is SWAP_ON, the arg parameter is used as a pathname of a file to enable swapping to. The misc parameter is used to set the priority of this swap device" in swapctl(2) and "If the device is already contained in the list, nothing is changed, in particular not its priority" after "The -a option requires that a path also be in the argument list. The path is added to the kernel's list of swap devices using the swapctl(2) system call" in swapctl(8). Jason? =;-) In any case, that's how it works. The kernel adds your wd0b before rc(8), rc(8) only does `swapctl -a`, not `swapctl -c`, so your nice entry in /etc/fstab gets ignored. My suggestion would be to add `swapctl -c -p 1 /dev/wd0b` to rc.local(8). But don't forget about it when reconfiguring your disks, or document it at the proper place in case of multiple admins. I do *not* suggest to compile a custom kernel containing something like "config bsd root on wd0a swap on wd1b" in its configuration file. In case you forget *that* and change your disk setup, you will be quite surprised. On top of that, if you encounter problems with a custom kernel, most people won't even try to help you because they assume you have just broken your kernel. As far as i understand config(8) and boot_config(8), you cannot modify the swap device used by an existing kernel after typing 'boot -c' at the boot prompt or `config -e -o /bsd.new /bsd` from the running system. Yours, Ingo -- Ingo Schwarze <[EMAIL PROTECTED]>
