I have to edit /etc/fstab to change mounting options for /dev/shm parameter.
source line is :
tmpfs /dev/shm tmpfs size=11g 0 0
I want to add noexec to the fourth field (mounting options) for the /dev/shm partition for many of servers.(with different size in mounting options)
So I tiried this code:
To obtain the value of mounting options. I used:
shmvar=`grep -E '\s/dev/shm\s' /etc/fstab | awk '{ print $4 }'`
the output is : size=11g
sed -i -e '/shm/s/$shmvar/$shmvar,noexec/' /etc/fstab
OR
sed -i -e '/shm/s/$shmvar/&,noexec/' /etc/fstab
but none of the sed commands worked.
while I use "size=11g" instead of "$shmvar" it works:
sed -i -e '/shm/s/size=11g/size=11g,noexec/' /etc/fstab
OR
sed -i -e '/shm/s/size=11g/&,noexec/' /etc/fstab
But because the "size" value is different in servers, I have to use variables
Would highly appreciate some quick help. Thanks
>Solution :
With GNU awk. If second field contains /dev/shm then append ,noexec to fourth field.
awk -i inplace 'BEGIN{ OFS="\t" } $2=="/dev/shm"{ $4=$4 ",noexec" } { print }' file
Output:
tmpfs /dev/shm tmpfs size=11g,noexec 0 0