9 commands to check hard disk partitions and disk space on Linux

http://www.binarytides.com/linux-command-check-disk-partitions

In this post we are taking a look at some commands that can be used to check up the partitions on your system. The commands would check what partitions there are on each disk and other details like the total size, used up space and file system etc.

Commands like fdisk, sfdisk and cfdisk are general partitioning tools that can not only display the partition information, but also modify them.

1. fdisk

Fdisk is the most commonly used command to check the partitions on a disk. The fdisk command can display the partitions and details like file system type. However it does not report the size of each partitions.

$ sudo fdisk -l

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x30093008

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *          63   146801969    73400953+   7  HPFS/NTFS/exFAT
/dev/sda2       146802031   976771071   414984520+   f  W95 Ext'd (LBA)
/dev/sda5       146802033   351614654   102406311    7  HPFS/NTFS/exFAT
/dev/sda6       351614718   556427339   102406311   83  Linux
/dev/sda7       556429312   560427007     1998848   82  Linux swap / Solaris
/dev/sda8       560429056   976771071   208171008   83  Linux

Disk /dev/sdb: 4048 MB, 4048551936 bytes
54 heads, 9 sectors/track, 16270 cylinders, total 7907328 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0001135d

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *        2048     7907327     3952640    b  W95 FAT32

Each device is reported separately with details about size, seconds, id and individual partitions.

2. sfdisk

Sfdisk is another utility with a purpose similar to fdisk, but with more features. It can display the size of each partition in MB.

$ sudo sfdisk -l -uM

Disk /dev/sda: 60801 cylinders, 255 heads, 63 sectors/track
Warning: extended partition does not start at a cylinder boundary.
DOS and Linux will interpret the contents differently.
Units = mebibytes of 1048576 bytes, blocks of 1024 bytes, counting from 0

   Device Boot Start   End    MiB    #blocks   Id  System
/dev/sda1   *     0+ 71680- 71681-  73400953+   7  HPFS/NTFS/exFAT
/dev/sda2     71680+ 476938  405259- 414984520+   f  W95 Ext'd (LBA)
/dev/sda3         0      -      0          0    0  Empty
/dev/sda4         0      -      0          0    0  Empty
/dev/sda5     71680+ 171686- 100007- 102406311    7  HPFS/NTFS/exFAT
/dev/sda6     171686+ 271693- 100007- 102406311   83  Linux
/dev/sda7     271694  273645   1952    1998848   82  Linux swap / Solaris
/dev/sda8     273647  476938  203292  208171008   83  Linux

Disk /dev/sdb: 1020 cylinders, 125 heads, 62 sectors/track
Warning: The partition table looks like it was made
  for C/H/S=*/54/9 (instead of 1020/125/62).
For this listing I'll assume that geometry.
Units = mebibytes of 1048576 bytes, blocks of 1024 bytes, counting from 0

   Device Boot Start   End    MiB    #blocks   Id  System
/dev/sdb1   *     1   3860   3860    3952640    b  W95 FAT32
                start: (c,h,s) expected (4,11,6) found (0,32,33)
                end: (c,h,s) expected (1023,53,9) found (492,53,9)
/dev/sdb2         0      -      0          0    0  Empty
/dev/sdb3         0      -      0          0    0  Empty
/dev/sdb4         0      -      0          0    0  Empty

3. cfdisk

Cfdisk is a linux partition editor with an interactive user interface based on ncurses. It can be used to list out the existing partitions as well as create or modify them.
Here is an example of how to use cfdisk to list the partitions.

Cfdisk works with one partition at a time. So if you need to see the details of a particular disk, then pass the device name to cfdisk.

$ sudo cfdisk /dev/sdb

4. parted

Parted is yet another command line utility to list out partitions and modify them if needed.
Here is an example that lists out the partition details.

$ sudo parted -l
Model: ATA ST3500418AS (scsi)
Disk /dev/sda: 500GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type      File system     Flags
 1      32.3kB  75.2GB  75.2GB  primary   ntfs            boot
 2      75.2GB  500GB   425GB   extended                  lba
 5      75.2GB  180GB   105GB   logical   ntfs
 6      180GB   285GB   105GB   logical   ext4
 7      285GB   287GB   2047MB  logical   linux-swap(v1)
 8      287GB   500GB   213GB   logical   ext4


Model: Sony Storage Media (scsi)
Disk /dev/sdb: 4049MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  4049MB  4048MB  primary  fat32        boot

5. df

Df is not a partitioning utility, but prints out details about only mounted file systems. The list generated by df even includes file systems that are not real disk partitions.
Here is a simple example

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda6        97G   43G   49G  48% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
udev            3.9G  8.0K  3.9G   1% /dev
tmpfs           799M  1.7M  797M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            3.9G   12M  3.9G   1% /run/shm
none            100M   20K  100M   1% /run/user
/dev/sda8       196G  154G   33G  83% /media/13f35f59-f023-4d98-b06f-9dfaebefd6c1
/dev/sda5        98G   37G   62G  38% /media/4668484A68483B47

Only the file systems that start with a /dev are actual devices or partitions.
Use grep to filter out real hard disk partitions/file systems.

$ df -h | grep ^/dev
/dev/sda6        97G   43G   49G  48% /
/dev/sda8       196G  154G   33G  83% /media/13f35f59-f023-4d98-b06f-9dfaebefd6c1
/dev/sda5        98G   37G   62G  38% /media/4668484A68483B47

To display only real disk partitions along with partition type, use df like this

$ df -h --output=source,fstype,size,used,avail,pcent,target -x tmpfs -x devtmpfs
Filesystem     Type     Size  Used Avail Use% Mounted on
/dev/sda6      ext4      97G   43G   49G  48% /
/dev/sda8      ext4     196G  154G   33G  83% /media/13f35f59-f023-4d98-b06f-9dfaebefd6c1
/dev/sda5      fuseblk   98G   37G   62G  38% /media/4668484A68483B47

Note that df shows only the mounted file systems or partitions and not all.

6. pydf

Improved version of df, written in python. Prints out all the hard disk partitions in a easy to read manner.

$ pydf
Filesystem Size Used Avail Use%             Mounted on                                 
/dev/sda6   96G  43G   48G 44.7 [####.....] /                                          
/dev/sda8  195G 153G   32G 78.4 [#######..] /media/13f35f59-f023-4d98-b06f-9dfaebefd6c1
/dev/sda5   98G  36G   61G 37.1 [###......] /media/4668484A68483B47

Again, pydf is limited to showing only the mounted file systems.

7. lsblk

Lists out all the storage blocks, which includes disk partitions and optical drives. Details include the total size of the partition/block and the mount point if any.
Does not report the used/free disk space on the partitions.

$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 465.8G  0 disk 
├─sda1   8:1    0    70G  0 part 
├─sda2   8:2    0     1K  0 part 
├─sda5   8:5    0  97.7G  0 part /media/4668484A68483B47
├─sda6   8:6    0  97.7G  0 part /
├─sda7   8:7    0   1.9G  0 part [SWAP]
└─sda8   8:8    0 198.5G  0 part /media/13f35f59-f023-4d98-b06f-9dfaebefd6c1
sdb      8:16   1   3.8G  0 disk 
└─sdb1   8:17   1   3.8G  0 part 
sr0     11:0    1  1024M  0 rom

If there is no MOUNTPOINT, then it means that the file system is not yet mounted. For cd/dvd this means that there is no disk.
Lsblk is capbale of displaying more information about each device like the label and model. Check out the man page for more information

8. blkid

Prints the block device (partitions and storage media) attributes like uuid and file system type. Does not report the space on the partitions.

$ sudo blkid
/dev/sda1: UUID="5E38BE8B38BE6227" TYPE="ntfs" 
/dev/sda5: UUID="4668484A68483B47" TYPE="ntfs" 
/dev/sda6: UUID="6fa5a72a-ba26-4588-a103-74bb6b33a763" TYPE="ext4" 
/dev/sda7: UUID="94443023-34a1-4428-8f65-2fb02e571dae" TYPE="swap" 
/dev/sda8: UUID="13f35f59-f023-4d98-b06f-9dfaebefd6c1" TYPE="ext4" 
/dev/sdb1: UUID="08D1-8024" TYPE="vfat"

9. hwinfo

The hwinfo is a general purpose hardware information tool and can be used to print out the disk and partition list. The output however does not print details about each partition like the above commands.

$ hwinfo --block --short
disk:                                                           
  /dev/sda             ST3500418AS
  /dev/sdb             Sony Storage Media
partition:
  /dev/sda1            Partition
  /dev/sda2            Partition
  /dev/sda5            Partition
  /dev/sda6            Partition
  /dev/sda7            Partition
  /dev/sda8            Partition
  /dev/sdb1            Partition
cdrom:
  /dev/sr0             SONY DVD RW DRU-190A

Summary

The output of parted is concise and complete to get an overview of different partitions, file system on them and the total space. Pydf and df are limited to showing only mounted file systems and the same on them.
Fdisk and Sfdisk show a whole lot of information that can take sometime to interpret whereas, Cfdisk is an interactive partitioning tool that display a single device at a time.
So try them out, and do not forget to comment below.

10 Tips to Push Your Git Skills to the Next Level

http://www.sitepoint.com/10-tips-git-next-level

Recently we published a couple of tutorials to get you familiar with Git basics and using Git in a team environment. The commands that we discussed were about enough to help a developer survive in the Git world. In this post, we will try to explore how to manage your time effectively and make full use of the features that Git provides.
Note: Some commands in this article include part of the command in square brackets (e.g. git add -p [file_name]). In those examples, you would insert the necessary number, identifier, etc. without the square brackets.

1. Git Auto Completion

If you run Git commands through the command line, it’s a tiresome task to type in the commands manually every single time. To help with this, you can enable auto completion of Git commands within a few minutes.
To get the script, run the following in a Unix system:

1 2	cd ~ curl https://raw.github.com/git/git/master/contrib/completion/git-completion.bash -o ~/.git-completion.bash

Next, add the following lines to your ~/.bash_profile file:

1 2 3

if [ -f ~/.git-completion.bash ]; then     . ~/.git-completion.bash fi

Although I have mentioned this earlier, I can not stress it enough: If you want to use the features of Git fully, you should definitely shift to the command line interface!

2. Ignoring Files in Git

Are you tired of compiled files (like .pyc) appearing in your Git repository? Or are you so fed up that you have added them to Git? Look no further, there is a way through which you can tell Git to ignore certain files and directories altogether. Simply create a file with the name .gitignore and list the files and directories that you don’t want Git to track. You can make exceptions using the exclamation mark(!).

1 2 3 4 5

*.pyc *.exe my_db_config/   !main.pyc

3. Who Messed With My Code?

It’s the natural instinct of human beings to blame others when something goes wrong. If your production server is broke, it’s very easy to find out the culprit — just do a git blame. This command shows you the author of every line in a file, the commit that saw the last change in that line, and the timestamp of the commit.

1	git blame [file_name]

And in the screenshot below, you can see how this command would look on a bigger repository:

4. Review History of the Repository

We had a look at the use of git log in a previous tutorial, however, there are three options that you should know about.

• --oneline – Compresses the information shown beside each commit to a reduced commit hash and the commit message, all shown in a single line.
• --graph – This option draws a text-based graphical representation of the history on the left hand side of the output. It’s of no use if you are viewing the history for a single branch.
• --all – Shows the history of all branches.

Here’s what a combination of the options looks like:

5. Never Lose Track of a Commit

Let’s say you committed something you didn’t want to and ended up doing a hard reset to come back to your previous state. Later, you realize you lost some other information in the process and want to get it back, or at least view it. This is where git reflog can help.
A simple git log shows you the latest commit, its parent, its parent’s parent, and so on. However, git reflog is a list of commits that the head was pointed to. Remember that it’s local to your system; it’s not a part of your repository and not included in pushes or merges.
If I run git log, I get the commits that are a part of my repository:

However, a git reflog shows a commit (b1b0ee9 – HEAD@{4}) that was lost when I did a hard reset:

6. Staging Parts of a Changed File for a Commit

It is generally a good practice to make feature-based commits, that is, each commit must represent a feature or a bug fix. Consider what would happen if you fixed two bugs, or added multiple features without committing the changes. In such a situation situation, you could put the changes in a single commit. But there is a better way: Stage the files individually and commit them separately.
Let’s say you’ve made multiple changes to a single file and want them to appear in separate commits. In that case, we add files by prefixing -p to our add commands.

1	git add -p [file_name]

Let’s try to demonstrate the same. I have added three new lines to file_name and I want only the first and third lines to appear in my commit. Let’s see what a git diff shows us.

And let’s see what happes when we prefix a -p to our add command.

It seems that Git assumed that all the changes were a part of the same idea, thereby grouping it into a single hunk. You have the following options:

• Enter y to stage that hunk
• Enter n to not stage that hunk
• Enter e to manually edit the hunk
• Enter d to exit or go to the next file.
• Enter s to split the hunk.

In our case, we definitely want to split it into smaller parts to selectively add some and ignore the rest.

As you can see, we have added the first and third lines and ignored the second. You can then view the status of the repository and make a commit.

7. Squash Multiple Commits

When you submit your code for review and create a pull request (which happens often in open source projects), you might be asked to make a change to your code before it’s accepted. You make the change, only to be asked to change it yet again in the next review. Before you know it, you have a few extra commits. Ideally, you could squash them into one using the rebase command.

1	git rebase -i HEAD~[number_of_commits]

If you want to squash the last two commits, the command that you run is the following.

1	git rebase -i HEAD~2

On running this command, you are taken to an interactive interface listing the commits and asking you which ones to squash. Ideally, you pick the latest commit and squash the old ones.

You are then asked to provide a commit message to the new commit. This process essentially re-writes your commit history.

8. Stash Uncommitted Changes

Let’s say you are working on a certain bug or a feature, and you are suddenly asked to demonstrate your work. Your current work is not complete enough to be committed, and you can’t give a demonstration at this stage (without reverting the changes). In such a situation, git stash comes to the rescue. Stash essentially takes all your changes and stores them for further use. To stash your changes, you simply run the following-

1

git stash

To check the list of stashes, you can run the following:

1	git stash list

If you want to un-stash and recover the uncommitted changes, you apply the stash:

1	git stash apply

In the last screenshot, you can see that each stash has an indentifier, a unique number (although we have only one stash in this case). In case you want to apply only selective stashes, you add the specific identifier to the apply command:

1	git stash apply stash@{2}

9. Check for Lost Commits

Although reflog is one way of checking for lost commits, it’s not feasible in large repositories. That is when the fsck (file system check) command comes into play.

1	git fsck --lost-found

Here you can see a lost commit. You can check the changes in the commit by running git show [commit_hash] or recover it by running git merge [commit_hash].
git fsck has an advantage over reflog. Let’s say you deleted a remote branch and then cloned the repository. With fsck you can search for and recover the deleted remote branch.

10. Cherry Pick

I have saved the most elegant Git command for the last. The cherry-pick command is by far my favorite Git command, because of its literal meaning as well as its utility!
In the simplest of terms, cherry-pick is picking a single commit from a different branch and merging it with your current one. If you are working in a parallel fashion on two or more branches, you might notice a bug that is present in all branches. If you solve it in one, you can cherry pick the commit into the other branches, without messing with other files or commits.
Let’s consider a scenario where we can apply this. I have two branches and I want to cherry-pick the commit b20fd14: Cleaned junk into another one.

I switch to the branch into which I want to cherry-pick the commit, and run the following:

1	git cherry-pick [commit_hash]

Although we had a clean cherry-pick this time, you should know that this command can often lead to conflicts, so use it with care.

Conclusion

With this, we come to the end of our list of tips that I think can help you take your Git skills to a new level. Git is the best out there and it can accomplish anything you can imagine. Therefore, always try to challenge yourself with Git. Chances are, you will end up learning something new!

How to Rescue a Non-booting GRUB 2 on Linux

http://www.linux.com/learn/tutorials/776643-how-to-rescue-a-non-booting-grub-2-on-linux

Figure 1: GRUB 2 menu with cool Apollo 17 background.

Once upon a time we had legacy GRUB, the Grand Unified Linux Bootloader version 0.97. Legacy GRUB had many virtues, but it became old and its developers did yearn for more functionality, and thus did GRUB 2 come into the world. GRUB 2 is a major rewrite with several significant differences. It boots removable media, and can be configured with an option to enter your system BIOS. It's more complicated to configure with all kinds of scripts to wade through, and instead of having a nice fairly simple /boot/grub/menu.lst file with all configurations in one place, the default is /boot/grub/grub.cfg. Which you don't edit directly, oh no, for this is not for mere humans to touch, but only other scripts. We lowly humans may edit /etc/default/grub, which controls mainly the appearance of the GRUB menu. We may also edit the scripts in /etc/grub.d/. These are the scripts that boot your operating systems, control external applications such as memtest and os_prober, and theming./boot/grub/grub.cfg is built from /etc/default/grub and /etc/grub.d/* when you run the update-grub command, which you must run every time you make changes.
The good news is that the update-grub script is reliable for finding kernels, boot files, and adding all operating systems to your GRUB boot menu, so you don't have to do it manually.
We're going to learn how to fix two of the more common failures. When you boot up your system and it stops at the grub> prompt, that is the full GRUB 2 command shell. That means GRUB 2 started normally and loaded the normal.mod module (and other modules which are located in /boot/grub/[arch]/), but it didn't find your grub.cfg file. If you see grub rescue> that means it couldn't find normal.mod, so it probably couldn't find any of your boot files.
How does this happen? The kernel might have changed drive assignments or you moved your hard drives, you changed some partitions, or installed a new operating system and moved things around. In these scenarios your boot files are still there, but GRUB can't find them. So you can look for your boot files at the GRUB prompt, set their locations, and then boot your system and fix your GRUB configuration.

GRUB 2 Command Shell

The GRUB 2 command shell is just as powerful as the shell in legacy GRUB. You can use it to discover boot images, kernels, and root filesystems. In fact, it gives you complete access to all filesystems on the local machine regardless of permissions or other protections. Which some might consider a security hole, but you know the old Unix dictum: whoever has physical access to the machine owns it.
When you're at the grub> prompt, you have a lot of functionality similar to any command shell such as history and tab-completion. The grub rescue> mode is more limited, with no history and no tab-completion.
If you are practicing on a functioning system, press C when your GRUB boot menu appears to open the GRUB command shell. You can stop the bootup countdown by scrolling up and down your menu entries with the arrow keys. It is safe to experiment at the GRUB command line because nothing you do there is permanent. If you are already staring at the grub> or grub rescue>prompt then you're ready to rock.
The next few commands work with both grub> and grub rescue>. The first command you should run invokes the pager, for paging long command outputs:

grub> set pager=1

There must be no spaces on either side of the equals sign. Now let's do a little exploring. Type ls to list all partitions that GRUB sees:

grub> ls
(hd0) (hd0,msdos2) (hd0,msdos1)

What's all this msdos stuff? That means this system has the old-style MS-DOS partition table, rather than the shiny new Globally Unique Identifiers partition table (GPT). (See Using the New GUID Partition Table in Linux (Goodbye Ancient MBR). If you're running GPT it will say (hd0,gpt1). Now let's snoop. Use the ls command to see what files are on your system:

grub> ls (hd0,1)/
lost+found/ bin/ boot/ cdrom/ dev/ etc/ home/  lib/
lib64/ media/ mnt/ opt/ proc/ root/ run/ sbin/ 
srv/ sys/ tmp/ usr/ var/ vmlinuz vmlinuz.old 
initrd.img initrd.img.old

Hurrah, we have found the root filesystem. You can omit the msdos and gpt labels. If you leave off the slash it will print information about the partition. You can read any file on the system with the cat command:

grub> cat (hd0,1)/etc/issue
Ubuntu 14.04 LTS \n \l

Reading /etc/issue could be useful on a multi-boot system for identifying your various Linuxes.

Booting From grub>

This is how to set the boot files and boot the system from the grub> prompt. We know from running the ls command that there is a Linux root filesystem on (hd0,1), and you can keep searching until you verify where /boot/grub is. Then run these commands, using your own root partition, kernel, and initrd image:

grub> set root=(hd0,1)
grub> linux /boot/vmlinuz-3.13.0-29-generic root=/dev/sda1
grub> initrd /boot/initrd.img-3.13.0-29-generic
grub> boot

The first line sets the partition that the root filesystem is on. The second line tells GRUB the location of the kernel you want to use. Start typing /boot/vmli, and then use tab-completion to fill in the rest. Type root=/dev/sdX to set the location of the root filesystem. Yes, this seems redundant, but if you leave this out you'll get a kernel panic. How do you know the correct partition? hd0,1 = /dev/sda1. hd1,1 = /dev/sdb1. hd3,2 = /dev/sdd2. I think you can extrapolate the rest.
The third line sets the initrd file, which must be the same version number as the kernel.
The fourth line boots your system.
On some Linux systems the current kernels and initrds are symlinked into the top level of the root filesystem:

$ ls -l /
vmlinuz -> boot/vmlinuz-3.13.0-29-generic
initrd.img -> boot/initrd.img-3.13.0-29-generic

So you could boot from grub> like this:

grub> set root=(hd0,1)
grub> linux /vmlinuz root=/dev/sda1
grub> initrd /initrd.img
grub> boot

Booting From grub-rescue>

If you're in the GRUB rescue shell the commands are different, and you have to load the normal.mod andlinux.mod modules:

grub rescue> set prefix=(hd0,1)/boot/grub
grub rescue> set root=(hd0,1)
grub rescue> insmod normal
grub rescue> normal
grub rescue> insmod linux
grub rescue> linux /boot/vmlinuz-3.13.0-29-generic root=/dev/sda1
grub rescue> initrd /boot/initrd.img-3.13.0-29-generic
grub rescue> boot

Tab-completion should start working after you load both modules.

Making Permanent Repairs

When you have successfully booted your system, run these commands to fix GRUB permanently:

# update-grub
Generating grub configuration file ...
Found background: /usr/share/images/grub/Apollo_17_The_Last_Moon_Shot_Edit1.tga
Found background image: /usr/share/images/grub/Apollo_17_The_Last_Moon_Shot_Edit1.tga
Found linux image: /boot/vmlinuz-3.13.0-29-generic
Found initrd image: /boot/initrd.img-3.13.0-29-generic
Found linux image: /boot/vmlinuz-3.13.0-27-generic
Found initrd image: /boot/initrd.img-3.13.0-27-generic
Found linux image: /boot/vmlinuz-3.13.0-24-generic
Found initrd image: /boot/initrd.img-3.13.0-24-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done
# grub-install /dev/sda
Installing for i386-pc platform.
Installation finished. No error reported.

When you run grub-install remember you're installing it to the boot sector of your hard drive and not to a partition, so do not use a partition number like /dev/sda1.

But It Still Doesn't Work

If your system is so messed up that none of this works, try the Super GRUB2 live rescue disk. The official GNU GRUB Manual 2.00 should also be helpful.