Linux

Dovecot: imap Error: open (/var/mail/username) failed

Error

While configuring mail on a Ubuntu Linux server running the Postfix mail server and Dovecot IMAP server, the following errors were observed in the mail log files,

dovecot: imap(user1): Error: open(/var/mail/user1) failed: Permission denied (euid=1002(user1) egid=1002(user1) missing +w perm: /var/mail, we're not in group 8(mail), dir owned by 0:8 mode=0775)
dovecot: imap(user1): Error: Failed to autocreate mailbox INBOX: Internal error occurred.
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tmpfs in Linux

tmpfs

1.0 tmpfs

tmpfs is a filesystem that resides in the main memory of a Linux system. In the case of disk files, a file is first fetched into the kernel pagecache and the delivered to the requesting process. The fetch part is not there in the case of tmpfs as the files are created and updated directly in kernel caches.… Read more

POSIX Shared Memory in Linux


1.0 Shared Memory

Shared memory is the fastest method of interprocess communication (IPC) under Linux and other Unix-like systems. The system provides a shared memory segment which the calling process can map to its address space. After that, it behaves just like any other part of the process's address space.… Read more

Shared memory

System V Shared Memory in Linux


1.0 Shared Memory

Shared memory is one of the three interprocess communication (IPC) mechanisms available under Linux and other Unix-like systems. The other two IPC mechanisms are the message queues and semaphores. In case of shared memory, a shared memory segment is created by the kernel and mapped to the data segment of the address space of a requesting process.… Read more

POSIX message queues in Linux


1.0 POSIX Message queues

POSIX interprocess comunication (IPC) was introduced in the POSIX.1b standard (IEEE Std 1003.1b-1993) for real time extensions. POSIX message queues have been made available in Linux since the version 2.6.6 (May 2004). POSIX IPC calls are as per the standard but may not be available on older Unix-like systems.… Read more

Interprocess communication using fifo

FIFOs in Linux


1.0 FIFO

FIFOs are pipes with a name and are also commonly referred to as named pipes. Pipes are common on Linux command lines but do not have a system-wide name. So, any two processes that wish to communicate using a pipe need to be related, either parent and child or, sharing a common parent, who sets up the pipe and passes its file descriptors to individual processes.… Read more