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Q: What does chmod 755 mean?

755 grants the owner read, write and execute (7), and the group and others read and execute (5). It is the standard permission for web directories and executable scripts.

Q: What is the difference between 644 and 755?

644 (rw-r--r--) is for regular files — owner can edit, everyone else can only read. 755 (rwxr-xr-x) adds the execute bit, needed for directories and runnable scripts.

Q: What chmod should I use for an SSH private key?

Use 600 (rw-------). SSH refuses keys that are readable by group or others.

Convert Linux file permissions between symbolic, octal, and binary instantly. Click any permission below to get started.

Octal notation

Symbolic (rwx)

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# Common permissions
chmod 755 web-file # rwxr-xr-x
chmod 644 document # rw-r--r--
chmod 600 id_rsa # rw-------
chmod 700 script.sh # rwx------

# Recursive
chmod -R 755 ./public

Frequently Asked Questions

What does chmod 755 mean?

755 grants the owner read, write and execute (7), and the group and others read and execute (5). It is the standard permission for web directories and executable scripts.

What is the difference between 644 and 755?

644 (rw-r--r--) is for regular files — owner can edit, everyone else can only read. 755 (rwxr-xr-x) adds the execute bit, needed for directories and runnable scripts.

How is the octal permission number calculated?

Each digit is the sum of read (4), write (2) and execute (1) for owner, group and other. So rwx = 4+2+1 = 7, r-x = 4+1 = 5.

What chmod should I use for an SSH private key?

Use 600 (rw-------). SSH refuses keys that are readable by group or others.