Dash
Dash is a minimalist POSIX-compliant shell. It can be much faster than Bash, and takes up less memory when in use. Most POSIX compliant scripts specify /bin/sh at the first line of the script, which means it will run /bin/sh as the shell, which by default in Arch is a symlink to /bin/bash.
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Installation
Install dash from the official repositories.
Use DASH as default shell
You can re-symlink /bin/sh to /bin/dash, which can improve system performance, but first you must verify that none of the scripts that aren't explicitly #!/bin/bash scripts are safely POSIX compliant and do not require any of Bash's features.
Identifying bashisms
Features of bash that aren't included in Dash ('bashisms') will not work without being explicitly pointed to /bin/bash. The following instructions will allow you to find any scripts that may need modification.
Install checkbashisms from the AUR.
Common places to check
- Installed scripts with a
#!/bin/shshebang:
$ find {,/usr}/bin -type f \
-exec grep -q -- '^#!/bin/sh' {} \; \
-exec checkbashisms -f -p {} +
- Package install scripts:
$ find /var/lib/pacman/local -mindepth 2 -type f -name install \
-exec checkbashisms -f -p {} + 2>&1 |\
grep -v -e '^you may get strange results' \
-e 'does not appear to have a #! interpreter line;$'
Relinking /bin/sh
Once you have verified that it won't break any functionality, it should be safe to relink /bin/sh. To do so use the following command:
# ln -sfT /bin/dash /bin/sh
Updates of Bash could overwrite /bin/sh. To prevent this, add the following line to the [option] section of /etc/pacman.conf:
NoExtract = bin/sh