It's my understanding that this limit can be increased only when you format the partition (at least on ext2/3).
That's correct. The number of inodes is calculated automatically at format-time based off of the number of bytes/inode you specify when formatting (or the default size, of course). For example, mkfs.ext2 uses the [-i bytes-per-inode] option and allows you to specify the number of inodes with -N (but i've never seen -N actually used).
hmm, now it's clear to me. As I have some spare space, when I recreate the partition I will just make it bigger and let the bytes-per-inode default
To change the number of inodes, you need to reformat. (We won't consider LVM-like options here, since that apparently doesn't apply to you.)
you're right, it doesn't apply
You shouldn't have to touch the /proc/sys files. Those are generated by the kernel and its drivers. Any changes you make will be lost at reboot, anyway, because /proc is an in-memory filesystem.
I think that those numbers can be changed in sysctl.conf to change them permanently but I was wondering whether these numbers were some kind of hard limit (i.e I thought that you could have more inodes on one partition but it should be no more than the limit I saw in /proc ). From your answer I understand that it's not the case Kind of curiosity: do you know how these numbers are estimated? Because I had a look on both a virtual machine and physical machines, both with SuSE 9.3 (i.e same kernel) and the numbers (file-max and inode-nr) are really differents. Thank you for the answer, Kind regards, Gaël