From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthias Kaehlcke Subject: Re: mount ramdisk rootfs /etc directory to jffs2 filesystem. Date: Wed, 20 Jan 2010 08:12:39 +0100 Message-ID: <20100120071239.GR16182@darwin> References: <20100119095024.GD16182@darwin> <20100119102026.GF16182@darwin> <20100119140600.GH16182@darwin> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-embedded-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="iso-8859-1" To: Johnny Hung Cc: Ricard Wanderlof , kernelnewbies , "linux-mtd@lists.infradead.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-embedded@vger.kernel.org" El Wed, Jan 20, 2010 at 10:32:15AM +0800 Johnny Hung ha dit: > 2010/1/19 Matthias Kaehlcke : > > El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit: > > > >> On Tue, 19 Jan 2010, Johnny Hung wrote: > >> > >>> Okay, I think the steps is below if my rootfs is ramdisk and conf= igure > >>> files in jffs2, > >>> > >>> 1. cp /etc/* /mnt/mtd/etc/ =A0 =A0(/mnt/mtd is my jffs2 fs) > >>> 2. rm -rf /etc/* > >>> 3. make symbolic links from all /etc/xx to /mnt/mtd/etc/xxx > >>> 4. remake ramdisk rootfs > >>> > >>> It seems all files in ramdisk rootfs /etc all links to /mnt/mtd/e= tc/ > >>> and try to modify these files is effective after reboot. > >>> But is this a common way in embedded linux ? > >> >=20 > Thanks, I understand. >=20 > >> In principle, but it is easier (and cleaner) to make a symbolic li= nk from > >> (say) /etc -> /mnt/mtd/etc without linking every individual file a= nd > >> directory. > > > > i totally agree with ricard when you want to move the entire direct= ory > > to jffs2 and not only some selected files > > > >> You could also use a jffs2 file system in flash for your rootfs, t= hat way > >> you wouldn't need a ramdisk at all. > > > > i'd also recommend you to consider if you really need the > > ramdisk. when using a ram disk its entire content is loaded to the = RAM > > occupying space, even if you don't use certain files (or part of > > them). other filesystems are more efficient in this aspect. > > if the main purpose is to have a read only rootfs, i'd suggest a lo= ok > > at squashfs. >=20 > I consider to use ramdisk as rootfs because worry about wrong > operation in rootfs (is use jffs2 rootfs) and it will cause system > boot up failed. you could set up a rootfs partition with a read-only file system (squashfs, jffs2 mounted ro) and a second partition that's writable. > Another query, does the syslogd/klogd log files also store in jffs2 > rootfs? Write to jffs2 frequently will reduce flash life cycle. by default the log files will be written to /var/log, if this directory happens to be on a jffs2 partition writes will go there and produce wear out. to avoid this you could set up a small tmpfs (in RAM) and mount it on /var --=20 Matthias Kaehlcke Embedded Linux Developer Barcelona We can't solve problems by using the same kind of thinking we used when we created them (Albert Einstein) .''`. using free software / Debian GNU/Linux | http://debian.org : :' : `. `'` gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `-