Partitioning Drives in Linux
Recommended Partitions
- /boot needs to be on its own partition, preferably /dev/sda1. You should make this plenty bigger than you need. If you go with 1GB, that should be much more than enough. 10GB would be overkill. I used to run systems with as small as 200MB /boot partition, but Fedora's preupgrade needs to stick stuff there so the bigger the better.
- You should have plenty of swap space, preferably on all your drives. The swap space should roughly equal the amount of memory you have. In general, your system should never swap, but if it needs to, you'll need enough swap space that the system will run until you can fix it.
- For the rest of the space, I prefer using LVM to manage it all. LVM allows you a lot of flexibility.
- Allocate only enough space as you need it. 20G should be enough for a good root partition---just the static stuff. Mount the directories in /var where a lot of data is used in its own partitions. For instance, I stick /var/lib/pgsql, the PostgreSQL data directory, in its own partition.
- /home lives in its own partition. 20GB is more than enough. If I use a lot of data, then I may extend it, or I may make a partition for the data.
- For backups, I sometimes have a prep area in a partition I mount at /backup. However, I don't trust this for long-term backup. For that, you need an external drive or an external server to store your data.
On a modern system, you only really need about 50GB of space for all your computing needs. Of course, you can get much larger drives for less than $50, and the smaller drives are hardly worth it. But eventually, we'll see Solid-State Drives get into the affordable range at 50GB, so you can think about mounting your root and home directories on an SSD and have your long-term, slow storage on a connected hard drive.
fdisk
fdisk -l will give you a list of your partitions on a drive.
# fdisk -l /dev/sda Disk /dev/sda: 80.0 GB, 80000000000 bytes 255 heads, 63 sectors/track, 9726 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x41ab2316
Device Boot Start End Blocks Id System /dev/sda1 * 1 25 200781 83 Linux /dev/sda2 26 156 1052257+ 82 Linux swap / Solaris /dev/sda3 157 9726 76871025 8e Linux LVM
# fdisk -l /dev/sdb Disk /dev/sdb: 80.0 GB, 80000000000 bytes 255 heads, 63 sectors/track, 9726 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00000081 Device Boot Start End Blocks Id System /dev/sdb1 * 1 2550 20482843+ 83 Linux /dev/sdb2 2551 2681 1052257+ 82 Linux swap / Solaris /dev/sdb3 2682 9726 56588962+ 8e Linux LVM
Swap
Use swapon to list your swap partitions that are currently engaged.
swapon -s shows you what swap partitions you have activated.
# swapon -s Filename Type Size Used Priority /dev/sdb2 partition 1052248 7120 -1 /dev/sda2 partition 1052248 0 -2
swapoff will remove a partition from swap.
# swapoff /dev/sda2 # swapon -s Filename Type Size Used Priority /dev/sdb2 partition 1052248 7120 -1
swapon will put a partition in swap.
# swapon /dev/sda2 # swapon -s Filename Type Size Used Priority /dev/sdb2 partition 1052248 7120 -1 /dev/sda2 partition 1052248 0 -2
Note that the swap partition has to be prepared as swap. You need to have it marked as swap according to fdisk ("Linux swap / Solaris") and then run mkswap on the partition before adding it to swap.
Removing a partition
To remove a partition, use fdisk.
# fdisk /dev/sda The number of cylinders for this disk is set to 9726. There is nothing wrong with that, but this is larger than 1024, and could in certain setups cause problems with: 1) software that runs at boot time (e.g., old versions of LILO) 2) booting and partitioning software from other OSs (e.g., DOS FDISK, OS/2 FDISK)
We want to see the partition table before we manipulate it. Use p to show the table.
Command (m for help): p Disk /dev/sda: 80.0 GB, 80000000000 bytes 255 heads, 63 sectors/track, 9726 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x41ab2316 Device Boot Start End Blocks Id System /dev/sda1 * 1 25 200781 83 Linux /dev/sda2 26 156 1052257+ 82 Linux swap / Solaris /dev/sda3 157 9726 76871025 8e Linux LVM
To delete a partition, use d.
Command (m for help): d Partition number (1-4): 2
View the partition table to ensure you did it right with p.
Command (m for help): p Disk /dev/sda: 80.0 GB, 80000000000 bytes 255 heads, 63 sectors/track, 9726 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x41ab2316 Device Boot Start End Blocks Id System /dev/sda1 * 1 25 200781 83 Linux /dev/sda3 157 9726 76871025 8e Linux LVM
Finally, write the changes to the table with w. Note that in this case, the partition table isn't written yet because the kernel is still using the drive.
Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. WARNING: Re-reading the partition table failed with error 16: Device or resource busy. The kernel still uses the old table. The new table will be used at the next reboot. Syncing disks.
Extend a Partition
Let's say you want to extend a partition. You'll need space after the partition on your drive. This can take some shuffling.
First, backup the data in the partition if you are worried at all of losing it. Here, I'm going to extend the /boot partition.
# cd /backup # tar zcf boot.tar.gz /boot tar: Removing leading `/' from member names
Now, make sure you are extending the right partition.
# df -h /boot Filesystem Size Used Avail Use% Mounted on /dev/sda1 190M 156M 25M 87% /boot
Next, you need to remove that mount point.
# cd / # umount /boot
Now, you should delete the partition and remake a new one of the bigger size. Note that there must be room free after the partition.
Use fdisk /dev/sda. Use p to see the partitions. Use d to delete partition 1. Then use n to create a new partition starting where it used to start and ending where you'd like it to end. Then finally w to write the changes to disk.
If you're using any partitions on the disk, then you'll need to reboot. After the reboot, umount the partition and then run resize2fs on the partition. It may complain about having to run e2fsck first. After that, mount the partition again and you should be good to go. Bold text
