ACTUALIZAR A CONTINUACIÓN
Ejecuto Kubuntu 14.04 en una computadora portátil Asus Prime UX32A que tiene una unidad SSD de 24 GB además del disco duro en el que está instalado el sistema operativo.
Desde que cambié a Ubuntu nunca pude usar la suspensión, la sesión se reanudaba inmediatamente después de haber cerrado la sesión del usuario.
Después de la investigación, parece que es la unidad SSD la que no se puede suspender. A continuación se muestra un extracto de Dmesg:
[ 163.713133] PM: Syncing filesystems ... done.
[ 163.886898] PM: Preparing system for mem sleep
[ 163.887309] Freezing user space processes ... (elapsed 0.001 seconds) done.
[ 163.889158] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
[ 163.890324] PM: Entering mem sleep
[ 163.891015] Suspending console(s) (use no_console_suspend to debug)
[ 163.891187] wlan0: deauthenticating from c4:3d:xx:xx:xx:39 by local choice (reason=3)
[ 163.933244] cfg80211: Calling CRDA to update world regulatory domain
[ 163.933412] sd 1:0:0:0: [sdb] Synchronizing SCSI cache
[ 163.933425] sd 0:0:0:0: [sda] Synchronizing SCSI cache
[ 163.933497] ata2.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
[ 163.933499] ata2.00: irq_stat 0x40000001
[ 163.933502] ata2.00: failed command: FLUSH CACHE
[ 163.933510] ata2.00: cmd e7/00:00:00:00:00/00:00:00:00:00/a0 tag 8
[ 163.933510] res 51/04:00:00:00:00/00:00:00:00:00/a0 Emask 0x1 (device error)
[ 163.933513] ata2.00: status: { DRDY ERR }
[ 163.933515] ata2.00: error: { ABRT }
[ 163.933543] sd 0:0:0:0: [sda] Stopping disk
[ 163.934043] ata2.00: configured for UDMA/133
[ 163.934047] ata2.00: device reported invalid CHS sector 0
[ 163.934055] ata2: EH complete
[ 163.934124] ata2.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
[ 163.934126] ata2.00: irq_stat 0x40000001
[ 163.934128] ata2.00: failed command: FLUSH CACHE
[ 163.934141] ata2.00: cmd e7/00:00:00:00:00/00:00:00:00:00/a0 tag 9
[ 163.934141] res 51/04:00:00:00:00/00:00:00:00:00/a0 Emask 0x1 (device error)
[ 163.934142] ata2.00: status: { DRDY ERR }
[ 163.934144] ata2.00: error: { ABRT }
[ 163.934509] ata2.00: configured for UDMA/133
[ 163.934512] ata2.00: device reported invalid CHS sector 0
[ 163.934519] ata2: EH complete
[ 163.934581] ata2.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
[ 163.934582] ata2.00: irq_stat 0x40000001
[ 163.934584] ata2.00: failed command: FLUSH CACHE
[ 163.934589] ata2.00: cmd e7/00:00:00:00:00/00:00:00:00:00/a0 tag 10
[ 163.934589] res 51/04:00:00:00:00/00:00:00:00:00/a0 Emask 0x1 (device error)
[ 163.934590] ata2.00: status: { DRDY ERR }
[ 163.934592] ata2.00: error: { ABRT }
[ 163.934947] ata2.00: configured for UDMA/133
[ 163.934949] ata2.00: device reported invalid CHS sector 0
[ 163.934954] ata2: EH complete
[ 163.934958] sd 1:0:0:0: [sdb]
[ 163.934959] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 163.934961] sd 1:0:0:0: [sdb]
[ 163.934964] Sense Key : Aborted Command [current] [descriptor]
[ 163.934965] sd 1:0:0:0: [sdb]
[ 163.934967] Add. Sense: No additional sense information
[ 163.934977] dpm_run_callback(): scsi_bus_suspend+0x0/0x40 returns -5
[ 163.934982] PM: Device 1:0:0:0 failed to suspend async: error -5
[ 164.506235] PM: Some devices failed to suspend, or early wake event detected
[ 164.506441] sd 0:0:0:0: [sda] Starting disk
[ 165.171009] iwlwifi 0000:02:00.0: L1 Disabled; Enabling L0S
[ 165.177816] iwlwifi 0000:02:00.0: Radio type=0x2-0x1-0x0
[ 165.270265] PM: resume of devices complete after 763.734 msecs
[ 165.270597] PM: Finishing wakeup.
[ 165.270599] Restarting tasks ... done.
¿Alguien tiene una idea de cómo solucionar el problema y solucionarlo?
Si es el SSD el que impide la suspensión, estaría bien deshabilitarlo por completo.
gracias de antemano
ACTUALIZACIÓN:
Encontré una solución alternativa enesta publicación
Apliqué la solución alternativa detallada en la respuesta validada y parece funcionar bien.