On Mon, 19 Jun 2017 10:44:23 +0000 "Blair, Charles E III" <c-bl...@illinois.edu> wrote:
> I am an unsophisticated user who has finally gotten > around to upgrading a desktop from wheezy to jessie. I am > trying to follow the instructions in the "release notes," > but don't really know what I'm doing. > > My current question is to clarify the instructions about > mounting partitions at the beginning of section 4.4. I > think I am supposed to issue as superuser the commands > > mount -o remount,rw / > mount -o remount,rw /usr > > Are there any other mount commands to issue before > apt-get upgrade ? How do I find out? I don't think > it matters, but this is a dual-boot using grub with > windows as the other system. > As an aside, do you have a separate partition for /usr? Most previous Debian installers suggested doing so as an option, but jessie after upgrade will be based on systemd and really isn't happy about a separate /usr. /usr is really required for boot nowadays, certainly with systemd. If your /usr is a separate partition, you can rebuild the initrd file to include /usr mounting instructions. Alternatively, you can merge /usr into /, which may be difficult if you previously went with the suggested few hundred MB size for / where /usr, /var and /home are on separate partitions. The voice of experience... As to mounting, the original purpose of /usr was to hold application code, which was never written to except for upgrade, and was shared by all users. Under those circumstances, it could be mounted read-only during normal use, to prevent accidental damage to it, or one user modifying something without realising that other users would be affected. If you're an 'unsophisticated user', you are unlikely to have set up the system in that way. Also, / may be mounted read-only after a serious boot error, so this is a warning to anyone who has a dodgy or exotic system to make absolutely sure that both / and /usr are mounted with writing enabled. You do also need /var and /home mounted, if they are separate to /, but if they were not mounted properly you would know about it already. I would guess also that it is possible to try an upgrade of a dead system using chroot, and again, you should check to make sure you know what's going on. A chroot is a meld of two systems, and it is relatively easy to make changes to the wrong one. Any package upgrade will require read-write mounting, and any problem here will be obvious very quickly. If you're upgrading a working, running system, than you can safely assume that the right things are mounted already. It's not a big risk, because one of the upgrade preliminaries is to make sure that your existing system is fully upgraded before the version upgrade is attempted, and any mounting problems would show up at that stage, long before anything irrevocable has happened. I suspect this warning exists because someone once had a mounting problem, and the upgrade did not follow the expected path, and they complained that the release notes did not take account of this possibility. Now they do. -- Joe