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: 

 

 

 

 

 

 655 for files: 

 

 

 Owner: Read (4) + Write (2) = 6 

 Group: Read (4) + Execute (1) = 5 

 Others: Read (4) + Execute (1) = 5 

 

 

 

 

 

 

 

 

 

 

 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 rsa 

 If 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@server01 

 Example 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" The authenticity of host 'server02 (192.168.x.x)' can't be established. ED25519 key fingerprint is SHA256:oZnvrgY+2Xpd2/huaffvzLMBAgI52AMPUmq/LPLIXbE. This key is not known by any other names Are you sure you want to continue connecting (yes/no/[fingerprint])? yes /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys r emuser@server02's password:  tput: No value for $TERM and no -T specified tput: No value for $TERM and no -T specified tput: No value for $TERM and no -T specified tput: No value for $TERM and no -T specified tput: No value for $TERM and no -T specified tput: No value for $TERM and no -T specified tput: No value for $TERM and no -T specified 

 Number of key(s) added: 1 

 Now try logging into the machine, with:   "ssh 'remuser@server02'" and check to make sure that only the key(s) you wanted were added. 

 

 

 

 

 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_keys 

 Optional: 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' INPUTFILE 

 Cop 

 

 

 -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. 

 

 

 s - The substitute command, probably the most used command in sed. 

 

 

 / / / - Delimiter character. It can be any character but usually the slash ( / ) character is used. 

 

 

 SEARCH_REGEX - Normal string or a regular expression to search for. 

 

 

 REPLACEMENT - The replacement string. 

 

 

 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. 

 

 

 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/g 

 

 Kill 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 .