How to change mount points

Question

I'm not very deep into this mounting/unmouting think on Linux, so here goes my question:

With df -h I get the following overview:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             323M  306M     0 100% /
tmpfs                 502M     0  502M   0% /lib/init/rw
udev                  497M  116K  497M   1% /dev
tmpfs                 502M     0  502M   0% /dev/shm
/dev/sda9              47G  181M   44G   1% /home
/dev/sda8             368M   12M  338M   4% /tmp
/dev/sda5             8,3G  1,1G  6,8G  14% /usr
/dev/sda6             2,8G  433M  2,2G  17% /var

I'm using this machine as web server where all web related stuff resides under /srv/. As this is part of / I'm out of disk space here. I saw /home having 44G available web space, which is pure nonsense in my case. So I want to have /home not as own partition (rather part of /), but /srv as own partition, grabbing the space consumed by /home. So after that df -h should look like this (/home replaced by /srv):

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             323M  306M     0 100% /
tmpfs                 502M     0  502M   0% /lib/init/rw
udev                  497M  116K  497M   1% /dev
tmpfs                 502M     0  502M   0% /dev/shm
/dev/sda9              47G  181M   44G   1% /srv
/dev/sda8             368M   12M  338M   4% /tmp
/dev/sda5             8,3G  1,1G  6,8G  14% /usr
/dev/sda6             2,8G  433M  2,2G  17% /var

What have to do to get here?

Answer 1

Since you have plenty of room in /home, move all the stuff from /srv into /home, then (optionally) move the stuff that was in /home to the root partition.

The simplest solution, if you don't mind a few minutes' downtime, is to move /srv into the larger partition and symlink it:

mv /srv /home
ln -s /home/srv /

If you really want to move /home to the root partition, then it takes a few renames. I assume there's no directory called /home/srv or /srv/srv.

mv /srv home
mkdir /srv
mount --move /home /srv
mv /srv/acme … /home/
mv /srv/srv/* /srv
rmdir /srv/srv

Finally (if you're not using the symbolic link method) edit /etc/fstab to change the mount point: on the line that begins with /dev/sda9 /home, replace /home by /srv.

Answer 2

Before you do anything you're going to have to figure out a place to keep the 180 megabytes of data that /home is currently taking up. I'd recommend repartitioning the current /dev/sda9 into, say, two gigs for /home and 42 for /srv.

Next up you're going to have to be a little tricky. This is all best accomplished in single user mode so that only root is logged on and you don't run into trouble with someone trying to access /home while you're moving it around.

You've got a decent amount of room in /var, so we'll use that as a temporary holding space: mkdir /var/tmp/oldhome

cd /home

`tar -cvf - ./ | ( cd /var/tmp/oldhome && tar -xvf - )

Now we've got /home backed up to someplace while we repartition /dev/sda9 into 2 gigs for /dev/sda9 and 42 gigs for /dev/sda10

Once you've finished repartitioning and creating new filesystems (I'm going to assume you know how to do this) you'll need to edit /etc/fstab.

Somewhere in there you'll see a line saying something along the lines of

/dev/sda9 /home ext3 defaults 0 2

Assuming that you've made /dev/sda9 the smaller of the two partitions, you can leave that line unchanged; you'll just need to add

/dev/sda10 /srv ext3 defaults 0 2

directly underneath.

Once those lines have been added, simply enter

mount /home ; mount /srv

and check with df -h to make sure both partitions are mounted.

Then replace the data from /home:

cd /var/tmp/oldhome

tar -cvf - ./ | ( cd /home && tar -xvf - )

Reboot your system in multi-user mode and everything should work.

Answer 3

As a quick but not very beautiful solution, you could remount a directory on one of your less-used disk to some point under /srv and move something there to clear a bit of space on /srv proper.

Read about --bind in man mount. It boils down to something like mount --bind /some/spare/dir /busy/dir/mountpoint. It works on any modern Linux.

Suppose that you have /srv/some/stuff.

• mkdir /home/offload/some/stuff — this is on the 44G free space partition
• mv /srv/some/stuff /srv/some/previous-stuff — temporarily, free up the name
• mount --bind /home/offload/some/stuff /srv/some/stuff — now some/stuff is on another partition!
• mv /srv/some/previous-stuff/* /srv/some/stuff — put things back under the original name, free up the space on /srv.