Technology Errors

PostgreSQL: ERROR: role “user” cannot be dropped because some objects depend on it

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When attempting to remove a user role from PostgreSQL it is possible to get an error. This error will be received if the role attempting to be removed still has access privileges for instance SELECT privileges on specific tables. Below I describe the error as well as how to remove access privileges for each table as well as a link to a previous article we wrote that will loop through every table within a specified database and revoke privileges.

Technology Insights

How To Remove Role Privileges Created By The PostgreSQL GRANT Command, Shell Script To Remove PostgreSQL Access Privileges

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PostgreSQL isn’t the most friendly when it comes to creating access to various databases or tables within those databases however with a couple easy shell scripts it becomes much easier. I previously wrote this article regarding a shell script created to provide SELECT access, which is essentially read only access, to every table located within a specified database. The problem now might be if you want to remove a user from having access to that database you will be required to manually remove each access privilege for the role you created. Below is the reverse of the initial shell script which will remove SELECT access from each table within a specified database.

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Send Mail Attachments Using mail Command From A Linux Shell

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One thing that can be really helpful for Linux administrators is sending mail attachments via the Linux command line. It is fairly widely known that you can inject text files into email by piping the outputs of those files to the mail command however something that is less known is attaching files to an email sent via mail. The information below describes how to send mail from a Linux shell using the mail command.

Technology Errors

Cannot Update Mailbox /var/mail/root For User Root. Error Writing Message: File Too Large

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Earlier today while looking into an issue on a CentOS Linux server I noticed an error message in the maillog file. The mail server running on this Linux server is Postfix and it appeared to have been complaining of the size of root’s mailbox located at /var/mail/root. When I first started investigating I figured I was going to see root’s mailbox at a size of 1GB or 2GB but I was surprised when looking into the issue that root’s mailbox was only about 48MB in size so at first I thought there might be another problem. After some digging around in /etc/postfix I figured out that Postfix limits the size of local mailboxes to 51200000 bytes or 48.8MB. Below is information on how I discovered the issue as well as how to modify the size that Postfix limits local mailboxes to.

Technology Insights

PostgreSQL: Run A SELECT Statement From A Linux Shell Using PSQL

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Earlier today I was troubleshooting some resource issues on a PostgreSQL server and needed to test some various SELECT statements to see if any of them were causing problems. I also wanted to verify the amount of resources a SELECT statement made using PGAdmin versus the amount of resources the same SELECT statement used running it directly on the Postgres server itself. Below is information on how to run a SELECT statement from a Linux shell. In this example the server is running CentOS Linux and PostgreSQL 8.4.4.