Can rootfs and /proc be readonly?

coffeecoffee · 09-26-2009, 09:43 PM

Hi

I'm trying to get my Debian system readonly (few reasons for this, but mainly it runs on compact flash and suits the system purpose).

In /etc/fstab I have all the necessary things either readonly or mounted as TMPFS. And / certainly behaves readonly in that I cannot write to it (obviously), and as you can see when I run the mount command:

Code:

/dev/hda2 on / type ext3 (ro,errors=remount-ro,data=ordered)

However when I run the mount command, I get three extra lines that concern me:

Code:

rootfs on / type rootfs (rw)
none on /sys type sysfs (rw,nosuid,nodev,noexec)
none on /proc type proc (rw,nosuid,nodev,noexec)

How can I get these to be read-only as well without breaking the system?

Any help appreciated, thanks.

syg00 · 09-26-2009, 10:00 PM

/proc and /sys are pseudo filesystems. They don't exist outside the kernel structures that describe them - whether "files" within them are "writeable" is determined by the (kernel/module) code that creates them.
For rootfs, see ../Documentation/filesystems/ramfs-rootfs-initramfs.txt in your source tree.

Short answer, none is a concern re your goals.

coffeecoffee · 09-27-2009, 12:30 AM

Quote:

Originally Posted by syg00

/proc and /sys are pseudo filesystems. They don't exist outside the kernel structures that describe them - whether "files" within them are "writeable" is determined by the (kernel/module) code that creates them.
For rootfs, see ../Documentation/filesystems/ramfs-rootfs-initramfs.txt in your source tree.

Short answer, none is a concern re your goals.

Thanks for the link. Just so I am 100% sure I am correct here, you are saying that since my / is readonly, /proc and /sys are readonly too?

And rootfs is essentially a RAM disk, therefore no disk writes occur when accessing it?

syg00 · 09-27-2009, 04:11 AM

Quote:

Originally Posted by coffeecoffee

... you are saying that since my / is readonly, /proc and /sys are readonly too?

I didn't say anything of the sort. For the purposes of this discussion, /proc and /sys don't exist. Period.
And if you have anything mounted at / (as you almost certainly will), the same applies to rootfs.