Dealing with “No space left on device” when partition is not full

When you get the “No space left on device” error on linux, first thing you do it to check your disk space usage.  Often times you notice you still have space, so what could be wrong?

Although your partition is not nearly full, most likely you have too many small or zero-sized files on your disk. So while you have enough disk space, all your available inodes have been exhausted. 

To check this run:

df -ih

If IUse percentage is at or near 100%, then huge number of small files is the reason for “No space left on device” errors.

To find out where inodes are being used run:

echo "Detailed Inode usage for: $(pwd)" ; for d in `find -maxdepth 1 -type d |cut -d\/ -f2 |grep -xv . |sort`; do c=$(find $d |wc -l) ; printf "$c\t\t- $d\n" ; done ; printf "Total: \t\t$(find $(pwd) | wc -l)\n"

After finding the directory with largest number of files, delete any unwanted files to free up some inodes. 

NOTE : If a process is using the files you are deleting, you will need a reboot to free the inodes used.

How to run a command on a filtered file list returned by grep

I often find myself passing a file list returned by some linux command to grep for filtering like below :

ls *.jar | grep test 

Sometimes i like to run a certain command on these filtered results. I achieve this by :

ls *.jar | grep test | while read line; do sha1sum "$line"; done

The generic form is :

<command generating a file list>   |   grep <filter keyword> | while read line; do <command> "$line"; done  

Best way to transfer large file or resume dropped ftp/scp file transfers

When transferring large files your first choice should be rsync, since it gives you the ability to resume unfinished/dropped transfers. However, if you started a large file transfer with ftp/sftp or scp and the connection was lost during the transfer, you don't need to start over again. Simply run rsync the following way and it will resume your transfer :

rsync --partial --progress --rsh=ssh <USER>@<HOST>:<REMOTE_FILE_PATH> <LOCAL_FILE_PATH> 

This command is what should be used for large file transfers.

How to find the 10 largest file or directories in Linux

This finds the largest 10 files :

find . -type f -print0 | xargs -0 du -s | sort -n | tail -10 | cut -f2 | xargs -I{} du -sh {}

This finds the largest 10 directories:

find . -type d -print0 | xargs -0 du -s | sort -n | tail -10 | cut -f2 | xargs -I{} du -sh {}

You can easily change -10 to -n where n is the number of files/directories you are trying to find.

How to receive or forward root emails in Linux

I find the following way the easiest way to manage who gets root's emails.

Open the file /etc/aliases for editing

vi /etc/aliases

Go to the bottom of the file where you see something similar to :

 # Person who should get root's mail
 #root:          marc

Change marc to the email address of the user who should get the email and finally uncomment the line. So for example your last two lines of /etc/aliases should look like:

# Person who should get root's mail
root:          you@yourcompany.com

Last step is to issue the following command ro reload /etc/aliases

newaliase