Linux - Bag of Tricks
Introduction
This document has many useful command.
Change Files and Folder Permissions
To change the permissions of files to 655 and subfolders to 755 (which is the common practice for directories to allow execution for navigating into them) within a specified directory and its subdirectories, you can use the find command with chmod.
Explanation of permissions:
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655 for files:
- Owner: Read (4) + Write (2) = 6
- Group: Read (4) + Execute (1) = 5
- Others: Read (4) + Execute (1) = 5
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755 for directories:
- Owner: Read (4) + Write (2) + Execute (1) = 7
- Group: Read (4) + Execute (1) = 5
- Others: Read (4) + Execute (1) = 5
Command
find /path/to/directory -type f -exec chmod 655 {} +
find /path/to/directory -type d -exec chmod 755 {} +
find /path/to/directory \( -type d -exec chmod 755 {} + \) -o \( -type f -exec chmod 644 {} + \)
chmod -R u+rwX,go+rX,go-w /path/to/directory
find /path/to/directory -type d -print0 | xargs -0 chmod 755
find /path/to/directory -type f -print0 | xargs -0 chmod 644
find /path/to/directory -print0 \
\( -type d -exec chmod 755 {} + \) \
-o \( -type f -exec chmod 644 {} + \)Linux Set Time Examples
You can also simplify format using following syntax:
date +%Y%m%d -s "20081128"To set time use the following syntax:
date +%T -s "10:13:13"Use the following syntax to set new data and time:
date --set="STRING"For example, set new data to 2 Oct 2006 18:00:00, type the following command as root user:
date -s "2 OCT 2006 18:00:00"OR
date --set="2 OCT 2006 18:00:00"Rclone Copy Examples
Click here for the page HERE
Rsync Copy Examples
This is to move files from one server to another
Ending the folder WITHOUT a “/” slash means copy that folder everything in that folder
Ending the folder WITH a “/” slash means copy everything within that folder
Example for “remote to local” location
rsync -chavzP --stats --progress -e ssh user@remote_host:/remote_folder/dir1/ /local_folder/dir1/Example for “local to remote” location
rsync -chavzP --stats --progress -e ssh /local_folder/dir1/ user@remote_host:/remote_folder/dir1/Rsync Auto Login while sending
Example to add a Rsync key on the remote server
On the local server simply login as a given user ex: ROOT or USER
ssh-keygen -t rsaIf it already exists simply hit "n"
| Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): /root/.ssh/id_rsa already exists. Overwrite (y/n)? |
If not then simply hit enter through all options
Example: of using ROOT
| Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /root/.ssh/id_rsa Your public key has been saved in /root/.ssh/id_rsa.pub The key fingerprint is: SHA256:JoMN/cxvsqZWBHws4eyrU5Q0F0qRe//44qdrrjiQmbU root@client01 The key's randomart image is: +---[RSA 3072]----+ | .+=.. | | =B.+ | | ..=O | | ==+o | | = E=... | | o... oo | | ..o..++ o | | .oo+o==*. | +----[SHA256]-----+ You have mail in /var/spool/mail/root |
Run the following to add the key to the remote server, you can also use IP instead of host name
ssh-copy-id -i ~/.ssh/id_rsa.pub remuser@server01Example of using a USER you will have to enter yes and the USER password
|
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub" Number of key(s) added: 1 Now try logging into the machine, with: "ssh 'remuser@server02'" |
Optional: If the command cannot be run above you can copy the key to the remote server manually into the “authorized_keys” file
cd
cd .ssh
vi authrized_keysOptional: Change the permissions on the local server
chmod 600 ~/.ssh/*
chmod 711 ~/.ssh
chmod 711 ~Synology Rsync
rsync -aXHmS --syno-acl /volum1/[xxx] /volume2/[xxx]-a, --archive archive mode; equals -rlptgoD (no -H,-A,-X)
-p, --perms preserve permissions
-X, --xattrs preserve extended attributes
-o, --owner preserve owner (super-user only)
-g, --group preserve group
--syno-acl copy Synology ACL data
I use the following options myself:
rsync -avhxWog --stats --backup --suffix $OLDSUFFIX --exclude-from=$RSYEXCL --syno-pseudo-root
No idea why I list options "og" since they're implied by -a, but it works...
Regards, Arild
PS: "rsync --help" lists all available options for rsync
Find and Replace String with sed
There are several versions of sed, with some functional differences between them. macOS uses the BSD version, while most Linux distributions come with GNU sed pre-installed by default. We’ll use the GNU version.
The general form of searching and replacing text using sed takes the following form:
sed -i 's/SEARCH_REGEX/REPLACEMENT/g' INPUTFILECop
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-i - By default, sed writes its output to the standard output. This option tells sed to edit files in place. If an extension is supplied (ex -i.bak), a backup of the original file is created.
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s - The substitute command, probably the most used command in sed.
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/ / / - Delimiter character. It can be any character but usually the slash (/) character is used.
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SEARCH_REGEX - Normal string or a regular expression to search for.
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REPLACEMENT - The replacement string.
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g - Global replacement flag. By default, sed reads the file line by line and changes only the first occurrence of the SEARCH_REGEX on a line. When the replacement flag is provided, all occurrences are replaced.
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INPUTFILE - The name of the file on which you want to run the command.
Find and Replace String with sed within vi
This is to search and replace a file globally withing vi
:%s/search_string/replacement_string/gKill Users in Linux
This is to be used when trying to kill users using the connection, replace the ? with the number of the session.
pkill -KILL -t pts/?Continued in Linux - Bag of Tricks (Part 2): Certificates, Databases, Disks & Boot.