Date: Sat, 4 Apr 2009 12:52:14 -0700 (PDT) From: Travis Daygale <anti_spamsys@yahoo.com> To: freebsd-hackers@freebsd.org Subject: compiling root filesystem into kernel (preferably tmpfs root filesystem) Message-ID: <313500.27821.qm@web37106.mail.mud.yahoo.com>
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In both the loader and kernel compiling doc, I see snippets of information = like this: #Make space in the kernel for a root filesystem on a md device.options MD_R= OOT_SIZE=3D10 boot_dfltrootInstructs the kernel to mount the statically compiled-in root = file system. My question is, how does one compile a root filesystem into the FreeBSD ker= nel? =A0When mounted, I want this root filesystem to run entirely in memory= with no other backing store (not even a readonly flash disc nor other back= ing media such as DVD/CD). The standard FreeBSD DVD install disc uses just such a root? =A0(Though see= ms to rely heavily on the rescue binaries being on a read only filesystem b= acked by the install DVD?) I'm still trying to reverse engineer how that wa= s done, without much luck. =A0 Is there a place/documentation I should be finding? =A0PicoBSD, NanoBSD, NF= S root diskless systems... all tantalizing close, but not the same thing (r= ead only roots backed by media other than memory). The root filesystem I'm wanting would presumably be in some conceptual sens= e similar to initramfs in Linux land, if that helps explain what I'm trying= to achieve. =A0In fact I have a Linux distribution which consists of a sin= gle giant kernel image and when boot, runs entirely in memory, the kernel i= n fact can't read filesystems other than tmpfs because no filesystems are c= ompiled in. =A0It appears all of this won't be possible in FreeBSD (looks l= ike ufs is required) but it appears I can get close to this. Indeed, I'd love a way for the root filesystem in FreeBSD to be of type tmp= fs, again similar to what is possible on the Linux side, though I'm much le= ss concerned with the type of filesystem (it just needs to be compiled into= the FreeBSD kernel and needs to be a memory backed filesystem when it moun= ts, no other backing store). Thanks in advance! Trever =0A=0A=0A
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